An in between job, CB72'66 and a C77'64

[jensen]

If I make it over to Europe someday, it would be a pleasure to look you up. Failing that, seeing these pictures of the local scenery (and motorcycles) is always a satisfying experience.

You're welcome "someday", and keep in mind that life is short, especially the healthy part.

Found some time to proceed the break-down of the CB72, starting with the rear fender. It took a lot of cleaning but eventually it was decent enough.



Unfortunately, somebody found it necessary to add more holes, probably for a different style tail light in its early life. The rear fender is decent, but needs a few small repairs before re-painting. The inside came out nicely, no hidden rust holes, large cracks etc,



Taking picture sis important, as we're getting older. The ground wire is, compared to the CB450, connected to a strange point, at the top of the front right engine hanger bold.



Tomorrow the frame will be parted from the engine, made all the preparations tonight.



And after an evening wrenching there are a lot of parts which have to be cleaned, plated, re-chromed or replaced.

 

[jensen]

Today I parted engine and frame. Since I'm careful with my back, and my sons weren't home, I had to be smart.



Did put some wood underneath the engine and lifted the table, disconnecting frame from engine was an easy job this way.



Pushed the engine to the rear of the motorcycle lift, and secured the engine (these engines are top-heavy.

 

[jensen]

Had a spare hour, so, top end time.



Always nerve wrecking, but everything came loose as it should...






Easy job, but will be replaced by an endless type:



Right piston skirt (back side):



Left piston skirt (back side):



strange pattern, wrong angle, probably a "do it yourself" honing job:



Good pliable rubber spacer wheel:



All parts off :



Next job is to split the cases, that will be a dirty job....

 

[ballbearian]

Those rings look like the older style wider top two rings.

 

[stl360+450]

It looks pretty clean from here, even that plug visible on the bench looks good to me. How long does cross-hatching typically last after a proper honing? Would I be correct to think that the at-home hone marks seem fresh and the motor did not accumulate a lot of miles after the last rebuild?

I'm also curious of your assessment of the skirt wear. Back side receives the most wear? Typical for the mileage?

A clip-style link on a cam chain?? Never seen that before. And, apparently Honda sold that style link for this motor?

 

[jensen]

Those rings look like the older style wider top two rings.

Don't know, I will take off the pistons somewhere this weekend for further measurement, and to analyze the skirts, but the pistons plus rings will be replaced anyway.

It looks pretty clean from here, even that plug visible on the bench looks good to me. Would I be correct to think that the at-home hone marks seem fresh and the motor did not accumulate a lot of miles after the last rebuild?

Yes, pretty clean indeed, I came across a lot of worse engines in the past. It looks like the engine was "rebuild" with minimal effort. I have to clean the pistons to see if they are std or overbore, but I think that the PO just cleaned the cylinder with a cheap hone job alone. The rings don't seem to be replaced, but maybe they are, we'll see tonight or tomorrow when examining the pistons. Either not a lot of miles after the hone job or tolerances between piston, rings and cylinder too wide. I also see blow-by on the pistons, but like I said, cleaning the pistons, cylinder and rings will give more detailed information.

How long does cross-hatching typically last after a proper honing?

That's a difficult question to answer, it depends on a lot of parameters. I have taken apart engines with less than 6000 km where the cross-hatching was gone, but I also have taken apart my CB450 K0 after 10.000 km and the cross-hatching was still in perfect shape. I have to say that it seems that a lot depends on engine construction, side forces on cylinder walls, tolerances, breaking-in process, riding style, amount of heat-cold cycles, and last but not least, oil quality.

I'm also curious of your assessment of the skirt wear. Back side receives the most wear? Typical for the mileage?

Not really, I took a picture of the backside because I was too lazy to take a picture from the front . Anyway, I'll take pictures when the pistons are dissembled from the rear, front and sides. I had just one hour to get the top-end off, and taking pictures at the same time, and since this thread is not really followed by many, people, I sometimes forget to take pictures of every step. I think these type of bikes are maybe a little too far away from the commodity bikes seen here at the forum (250, 350, and 450's mainly). The 250 / 305 department on this forum is maybe an underachiever .

A clip-style link on a cam chain?? Never seen that before. And, apparently Honda sold that style link for this motor?

The answer can be found in the exploded view above, as you can see. I don't like them, and will be replace by an endless camchain (and a stronger one too). Remember, this bike was designed in 1960, and was one of the earliest "over the counter" sports-bikes in the world. Honda learned from their mistakes, and in this bike there are a few to take into account.

One of these "mistakes" or as I rather call them "design flaws" is the type of cam chain. Other "design flaws"are :

- Primary chain drive, not only prone to wear, bur also making the primary transmission shaft running in the "wrong" direction.
- Counter shaft used as kickstarter shaft, due to the "wrong" direction of the primary shaft.
- Transmission gears are prone to wear due to local hardening failures on gears, straight dogs, no undercut to keep the transmission in gear.

And many others (less significant) "design flaws" or "learning curve" of Honda engineers.

Btw, thanks for following and responding to this thread, this way I keep motivated to proceed.

 

[ballbearian]

Bill Silver says the thicker rings were discontinued due to increased friction and a loss of performance.

It also appears that you have the earlier narrow cam chain adjuster housing with the 32mm bolt spacing. My 64 CA77 uses the later 41mm spacing. It is curious that your push rod for that is so extended, perhaps the housing there has a longer hole in it. Here is one I'm modifying to replace the hardened rubber wheel with a removeable bolt and reproduced wheel.

How old is your motor? As you said there has been quite a few design changes, many of them within the first 2-3 years of the 250/305 production.

 

[stl360+450]

Btw, thanks for following and responding to this thread, this way I keep motivated to proceed.

My pleasure. It's a great opportunity to learn, not just about the 305 models, but how to assess any used motorcycle from top to bottom during a restoration or rebuild.

Thank you for taking time to answer questions, e.g., the one about cross-hatching. I hadn't even considered the possibility of reusing the rings with greater clearances, but given the DIY (do-it-yourself) hone work, that could very well be.

Honda learned from their mistakes, and in this bike there are a few to take into account.

I enjoyed reading about these. The evolution from these bikes to the next generation wasn't just about motor size, but also engineering advancements.

I think these type of bikes are maybe a little too far away from the commodity bikes seen here at the forum (250, 350, and 450's mainly).

Parts availability seems to be a concern with the 250/305 models — scared me away from them early on. For those of us who got into the hobby later, it would be a costly enterprise. Luckily, I'm more drawn to the 70s styling, anyways.

 

[boddy]

since this thread is not really followed by many, people

I think a lot of people follow your threads no matter the model of bike you are working on. I enjoy your threads and the knowledge you pass on.

 

[ancientdad]

I think a lot of people follow your threads no matter the model of bike you are working on.

Almost 500 views in 14 days since it started, I'd say many are viewing it.

 

[jensen]

I think a lot of people follow your threads no matter the model of bike you are working on. I enjoy your threads and the knowledge you pass on.

Almost 500 views in 14 days since it started, I'd say many are viewing it.

I didn't look at the followers, my error, but more to the responses I got. I noticed that the last four additions to this thread were mostly mine.

 

[ancientdad]

I noticed that the last four additions to this thread were mostly mine.

Not unlike most of my threads, a small number of members following and responding but mostly my posts. Personally, I just enjoy sharing what I've done, it helps me better enjoy the other hours I spend here while doing my everyday job.

 

[jensen]

Personally, I just enjoy sharing what I've done, it helps me better enjoy the other hours I spend here while doing my everyday job.

Me too, but to find the level of detail you put in a thread is measured by the remarks and questions, there is nothing else.

 

[Davomoto]

It also appears that you have the earlier narrow cam chain adjuster housing with the 32mm bolt spacing. My 64 CA77 uses the later 41mm spacing. It is curious that your push rod for that is so extended, perhaps the housing there has a longer hole in it. Here is one I'm modifying to replace the hardened rubber wheel with a removeable bolt and reproduced wheel.

How old is your motor? As you said there has been quite a few design changes, many of them within the first 2-3 years of the 250/305 production.

Other way around. The early tensioners were wider, late narrower. Change occurred in 66 iirc. Very cool remaking the tensioner wheel hopefully works out well!

 

[ballbearian]

Other way around. The early tensioners were wider, late narrower. Change occurred in 66 iirc. Very cool remaking the tensioner wheel hopefully works out well!

I also have my friends 65 CA77 (5xxxxxx) in my trailer I can check, but I'm sure it's the wide body also. Bill silver states the change occurred at CB72E-1007137, in his restoration guide. I only have first hand experience with the C/CA motors, but there are usually similar aspects to the CB/CL models, like Jensen's.
His motor does seem to be a fairly early example.

Oh, and thanks for the encouragement on the wheel repop project. I hope I can get it done before I really need it! I'd bet Jensen has some spares for his, if needed.

 

[jensen]

Yes, I did read this (at the beach), CB72E-1007137, mine is 10075xx. In the meantime, I did the measurements on the pistons and cylinders, but first I examined them visually.



Earlier, I wrote this :

Yes, pretty clean indeed, I came across a lot of worse engines in the past. It looks like the engine was "rebuild" with minimal effort. I have to clean the pistons to see if they are std or overbore, but I think that the PO just cleaned the cylinder with a cheap hone job alone. The rings don't seem to be replaced, but maybe they are, we'll see tonight or tomorrow when examining the pistons. Either not a lot of miles after the hone job or tolerances between piston, rings and cylinder too wide. I also see blow-by on the pistons, but like I said, cleaning the pistons, cylinder and rings will give more detailed information.

I think I nailed it, standard pistons, first set of piston rings (not changed), and a "do it yourself" hone job, maybe just for de-glazing, who knows



Piston pin clip gap positioned wrong:



Lots of blow-by:



Traces of corrosion:



Strange rough surface at the back of the pistons (both):



Deep groves, wonder if 0,5 mm overbore is enough (don't think so):



More closely:



Piston ring gap larger than 0,5 mm (0,6 wasn't fitting, and I don't have a 0,55 mm). And that was in the area where the piston rings aren't going. In the area where the piston rings slide, the gap went to 0,7 mm. On top of that, the piston itself had way too much play in the cylinder, not even bothered to measured.



Piston pins also have to be replaced:



And last but not least, two different plugs (heat range)

 

[stl360+450]

Do those two lines around the circumference of the wrist pin ultimately lead to excessive free play for the piston on the pin? Is this an area where one judges by eye or by micrometer?

I just ordered my textbook.

 

[ballbearian]

The moderate wrist pin wear is a good sign the small end rod bushings are usable. I'm sure G-man would've said if they were worn too much.

I've seen a hotter plug used to combat blow-by, but ring wear is what it is.

Hard to be 100% sure that the cylinder is original to your motor, it's possible that it was an earlier one, or much later, according to Davomoto.

 

[jensen]

Do those two lines around the circumference of the wrist pin ultimately lead to excessive free play for the piston on the pin? Is this an area where one judges by eye or by micrometer?

Since this bearing (small-end bearing) is the most critical bearing in the whole engine, and piston pins are cheap, I always change them, no matter what. In this case, I measured the piston pin at 3 places twice (90 degrees in between the measurements for detection ovality, two measurements at the piston pin ends of both sides, and one in the middle). The biggest difference was 0,02 mm, between the piston pin ends and the middle. To answer your question, visually I would replace them based on the radial scoring pattern in the mid-section, not directly for the brown rings.

I just ordered my textbook.

What do you mean by this ?

The moderate wrist pin wear is a good sign the small end rod bushings are usable. I'm sure G-man would've said if they were worn too much.

The crank in the engine feels right, the play on the small rod end is good, and visually no issues. I checked the play with a NOS piston pin, and it felt good on both sides.



No deep scoring, strange patterns etc. The crank, as far as I can see for now, is good to go, but has to be taken apart for cleaning and maybe some replacement rollers. I will replace the crank by the one that G-man checked, and this will be in my stash for later refurbishment.

I've seen a hotter plug used to combat blow-by, but ring wear is what it is.

The quality of the engine work tells me that the PO didn't do this on purpose, I guess he / she didn't have anything else lying around.

Hard to be 100% sure that the cylinder is original to your motor, it's possible that it was an earlier one, or much later, according to Davomoto.

Yes, I'm almost 100% sure that this is the right cylinder for this engine, and original, but will look into that later.



Here is a copy of the E (engine) numbers for the cam chain tensioner. It says that for the CB72, from 1036507 the tensioner changed, I have CB72E-10075xx. The number mentioned by Dave is for the CB77 only, not for the CB72. However, Dave cited the book of Bill Silver correctly, as Bill Silver writes that there are two changes, made at the same time (?), the bolt pattern and the position of the adjuster bolt, and that these changes were made at CB72E-1007137. However, the information in the parts manuals state that this is correct for the CB77, but not for the CB72 (as you can see in the picture above). In the past, I had some discussion on the 305 forum about the years and numbers, and find that the information in the original series of the parts manuals (I have all numbers and more) is not always the same as in the Bill Silver manuals.

In the past, when engines for these bikes could be picked-up for virtually free, I collected a few, the engines and these numbers I have:

CB72E-1101xx
CB72E-1111xx
CB72E-1500xx
CB72E-2101xx
CB72E-2125xx
CB72E-3137xx

CB72E-4002xx, type 2 crank
CB72E-4018xx

CB72E-10003xx
CB72E-10016xx
CB72E-10108xx

CB77E-2105xx

I also have engine parts from a 1959 / 1960 engine with a rotating gear shift pattern, probably one of the first bikes in the Netherlands, imported "unofficially" to exhibit in 1960 at the motor fare in Amsterdam. This bike has been seen by Cornelis van der Heuvel, an expert on the Japanese bikes in the Netherlands, he also wrote a book about the early Japanese bikes, named "Pictorial history of Japanese motorcycles", written in English. Sometimes this book pops up on Ebay.

Furthermore, there are also a lot of wrong bolts used on this bike, many original (small) steel bolts are replaced with stainless steel, or even a steel bolts with a 13 mm head instead of a 12 or 14 mm head.

The only thing I know is that the engine and frame numbers are close, so I believe the original cases for this frame, it has the alloy front fork, that the VIN number is 1967, but the bike is a 1966. The last digit of the VIN number is stamped in the plate in the Netherlands, not in Japan.

I also tend to believe that the speedo / tacho assy (a1964-1967 model with 31455 km) is original too. Looking at the breaks, the overall condition of the bike, the odometer and the number of previous owners (3) are all in line.

Overall, the bike is taken care for by the PO's, but lacked the money, or time to do the engine rebuild properly. Don't forget that these bikes were almost worthless in the late 70's, and used as a cheap commuter bike at that time, in summer and winter (that explains why all bolts used for the mudguards, front and rear fork are replaced by stainless ones). I was happy the PO did this, because now it was a piece of cake to remove those. I'm also happy that someone was in the engine (top-end) as well, makes my work easy, and as long there is no damage, it works for me. However, I don't think the engine bottom case was opened in the past, by after cleaning we will see.

 

[ballbearian]

Sadly, I was not involved during the active times at the 305 forum. I'm sure there was a lot of good information there. I don't think there were very many 250cc models sold in the US, compared to the 305's.
You do have a great candidate for working on that was, at least, cared for. Those rod bushings would make me smile.

 

[jensen]

I wrote a lot about these bikes on the 305 forum, under the name jensen and later under jensey, because there were some problems with my account for some unknown reason. Virtually all CB77's went to the US, and most CB72's went to Europe and the rest of the world.

 

[stl360+450]

I just ordered my textbook.

What do you mean by this ?

I ordered a binder copy of Bill Silver's 250/305cc Engine Repair Guide. I figure it will be an interesting document to look through while following this thread.

 

[jensen]

I wasn't sure you meant that, so I asked. Sometimes it's difficult for me to understand what is written, sometimes it's a serious remark like this, sometimes a saying or a (local) expression, or even slang

 

[jensen]

I ordered a binder copy of Bill Silver's 250/305cc Engine Repair Guide. I figure it will be an interesting document to look through while following this thread.

Now you need to buy one (a CB72/77 / CL72/77). These (sports) bikes are the beginning of an era that lasts until today. I started to collect these bikes and parts in the '80's, way before I started with the CB450's. For me, these are the nicest bikes of that time, certainly very popular in Europe (dreams and CB72), and as far I know, also in the US, but mainly dream, CB77 and the CL's). The CL's were never imported (officially) in the Netherlands, a pity, because these bikes are very nice to see.

Today I was going through some old boxes of photo's and books (my wife and me are clearing out the house, thinning out everything what pilled up over the years) and found a long-lost picture of one of my first mopeds, a Zundapp KS50. After I sold this moped, got a Yamaha FS1, also the last 2-stroke moped, and went into 4-stroke with the Honda C50-H, the start of my Honda "addiction". Unfortunately, I don't have a picture (as I know of) of the Yamaha FS1, also not my Kreidler, the first moped I owned.

 

[stl360+450]

I wasn't sure you meant that, so I asked. Sometimes it's difficult for me to understand what is written, sometimes it's a serious remark like this, sometimes a saying or a (local) expression, or even slang

It's easy to forget that you are a non-native speaker — I will try to write more plainly or (more likely) add extra information so you can learn the slang without needing to ask.

Now you need to buy one (a CB72/77 / CL72/77).

We will see. At the very least, I will first need to thin out everything that piled up in my garage over the years. We have a saying in the US (probably everywhere) about eating that a person (often a child) should not ask for seconds (a second portion) while there is still food on their plate. In this case, I have some unfinished projects that should be closed before I would consider taking on another bike.

Today I was going through some old boxes of photo's and books (my wife and me are clearing out the house, thinning out everything what pilled up over the years) and found a long-lost picture of one of my first mopeds, a Zundapp KS50.

I bet it was a pleasure to find that photograph. Did you customize the KS50? I'm surprised to see a disc brake.

 

[jensen]

I bet it was a pleasure to find that photograph. Did you customize the KS50? I'm surprised to see a disc brake.

O yes, I remembered this bike, but over the years memory starts changing the details. I forgot about the disk brake, which is indeed an add-on from a later model, if my memory serves well. I remember how fast this moped was, with 70 cc kit, expansion muffler (I added this later, not pictured) and a 16 mm bing carburetor it did easily 80km/hr. The fuel tank was huge compared with the later Yamaha FS1, which resulted in a long walk to the nearest gas station when I acquired the Yamaha. I don't think the clutch cable was routed correctly, but I forgive myself, I was 16 years old.

The build quality was slightly better than Honda from that era, stainless steel front mudguard, plastic rear mudguard, large 12V/35W headlight, good suspension and a speedo / tacho unit. The frame itself was made for the KS50 and KS80, so the moped could easily handle more power. The Honda SS / CD did have steel mudguards, low light output, only a speedo and a frame and rear fork plus suspension that couldn't handle a 70cc combined with high lift cams (necessary to reach the same speed as the Zundapp with 70cc high output cylinder.

 

[jensen]

Yesterday evening I had an hour spare, so back to the garage and disassemble the cylinder head. In the past I disassembled many 250 / 305 heads, and learned a few things on the way. Normally, when the head is never touched by a PO, it can be quit challenging, especially when moisture or high mileage are part of the deal.

In this case someone was in the head in an earlier stage, plus the bike stood in a dry, relative warm environment, so the job was easier then normal.

Starting with the ignition cover. I secure the head on wooden blocks with the back against the wall (protected with a piece of wood), this way I can push the (JIS) screwdriver really hard into the bolt with my sternum (I made a special piece of wood where the end of the (JIS) screwdriver is centered, dividing the pressure over my chest). Now I have two hands free, one to hold the screwdriver, the other one for tuning the screwdriver with a wrench. I could do it with a impact driver, but since the aluminum threads of these heads are vulnerable and sensitive for shock-load / impact, I choose not too if possible.



In these bikes, the camshaft is composed of three parts, the left- and right camshaft, and center sprocket. The advance mechanism, including the springs are build in the sprocket, thus if you have to replace the point shaft, or the advancer springs you have take the engine out, remove the top cover, etc. Not a wrench friendly solution, that's one of the reasons to avoid using the advancer and use an electronic ignition (Sachse) with build in electronic advancer. However, I keep the points-shaft and springs in place for points ignition when needed when the electronics break down.



All bolts are spared, and re-usable after cleaning and re-plating.



Like pointed out earlier, the points are not in a healthy state and are being replaced on the spare points plate.



The backside revealed black dust, this can be particles of plastic from the points (likely), coal from the exhaust fumes (unlikely), rubber from the oil-seal (likely) points-dust due to a bad condenser (most likely). I have to analyze this further to get to the bottom if it, never seen that in this amount.



The other side came loose too, and again all bolts are saved and re-usable after plating.





As you can see in the picture below, Honda-bond is used in huge quantity's, luckily it's Honda-bond and no silicon gasket. I had some issue's to get the follower shaft out, Honda-bond was applied there as well.



Unfortunately, all four valve covers are damaged, either by the PO or by me. After taking these of with heat and a chisel I saw why these were so stubborn. No O-rings were used, but instead, a large amount of Honda-bond on the surface AND thread did the trick



Once the head is off, there is no easy way to hold the camshaft from turning to get the bold of the clamp mechanism from the clamp bolt at the tacho side.



The easiest way I found is to use the cam-chain itself, works always like a charm. Now the camshaft is secured, the nut at the end of the R/H camshaft can be loosened.



This is the nut, and secures the clamping bolt. In most cases this nut is tight, very tight, also at this bike. After loosening, the bolt has to be hit with the nut still on it (to avoid damaging the internal advance mechanism). Before hitting the nut you have to secure the camshaft sprocket too, otherwise the whole camshaft will move, including the bearings, and that is something to be avoided at this stage.



I place a heavy piece of copper on top of the nut and give it a punch with a steel hammer, in most cases the bolts will come loose after one blow. As you can see in the picture, the bolt came loose, and is resting on the nut. I sprayed a lot of penetrating oil around the threads of the cam sprocket nut, because I think it will not give up without a fight (this will be one of the few times that you'll see me using a hammer).



Next step is to take out the camshafts, remove all valves, and decide If I can re-use this head or pick another one out of my stash. Enough too choose from, 40+ cylinders and heads available from all years.



It took a lot of work to categorize everything, but now I can make a picture of the CB72/77 and dream cranks in one place. every box contains 3 complete (used) cranks, and there are six boxes. Every crank is labeled, and there is a short description per crank of engine number, general state and a measurement report. With my press, some guiding of G-man for the tricks on these cranks, and some machines around me, I don't have to be bored after my retirement

 

[ancientdad]

I've never seen Hondabond in that color, my first thought was silicone sealer.

I secure the head on wooden blocks with the back against the wall (protected with a piece of wood), this way I can push the (JIS) screwdriver really hard into the bolt with my sternum (I made a special piece of wood where the end of the (JIS) screwdriver is centered, dividing the pressure over my chest). Now I have two hands free, one to hold the screwdriver, the other one for tuning the screwdriver with a wrench.

This is where a JIS T-handle would come in handy.

 

[jensen]

Preliminary conclusion until now:

Overall, I'm surprised of the quality of work from the PO(s), not much was broken, damaged or destroyed. However, I don't understand why someone would use so much Honda-bond, but I'm glad that it is Honda-bond and not something else. And for me it's a complete puzzle why someone would use Honda-bond for the valve covers instead of the designated O-rings.. These covers are hard to get, and made of really soft aluminum, very vulnerable using the wrong torque or the wrong tools.

I'm also glad that the PO did replace the cam-sprocket for a NOS cam sprocket, including the springs. I have seen many cam sprockets, not one with this amount of km's was that clean, and had that good and stiff springs. I also noticed that he /she didn't replace the nut, as I can see the chisel marks

Furthermore, the cams look like new, just as the followers, but measurements have to reveal if they are. This week, when I have a few spare hours, I'll take the cams out after loosening the sprocket nut.

 

[jensen]

This is where a JIS T-handle would come in handy.

I tend to agree, and I have them, but I like my JIS screwdriver better for these kind of situations, due the fact that I can put a wrench on it (nr.13), and really press it in the bold. Did you see the amount of Honda-bond at the threads (did you notice the layer of Honda-bond at the bolt holes in the left sidecover)? Almost impossible to get them out without damaging with a (JIS) T-handle. the amount of force I had to apply to the (large) JIS screwdriver was immense, especially the left side.

 

[ancientdad]

I tend to agree, and I have them, but I like my JIS screwdriver better for these kind of situations, due the fact that I can put a wrench on it (nr.13), and really press it in the bold. Did you see the amount of Honda-bond at the threads (did you notice the layer of Honda-bond at the bolt holes in the left sidecover)? Almost impossible to get them out without damaging with a (JIS) T-handle. the amount of force I had to apply to the (large) JIS screwdriver was immense, especially the left side.

I saw the pictures, yes. You didn't address my question about the orange Hondabond, I've never seen it that color which makes me wonder about it.

 

[ballbearian]

Great pictures of this part of the process. I found several damaged broken JIS screws for the cam support bearings on mine. I used the Vessel Impacta screwdriver to remove them. Supporting the camshaft while loosening the expansion bolt and nut like you did was great. I found loosening the locking collar, with it's reverse thread, on the advancer to be quite interesting also.
Removing the camshaft halves with their bearings was also quite a challenge.

 

[jensen]

I've never seen Hondabond in that color, my first thought was silicone sealer.

I'm sorry, it escaped my attention. I have a very old tube of Honda-bond in this color brownish / red, that's why I think it's Honda-bond. It might be something different, but it feels the same,

 

[jensen]

I found loosening the locking collar, with it's reverse thread, on the advancer to be quite interesting also.

Did you know that there are two types of locking collars ?, One with normal thread and one with reverse thread ? I have both, NOS and used.

Removing the camshaft halves with their bearings was also quite a challenge.

Yes, it is, certainly at room temperature. I do heat up the whole cylinder head in my glass oven and remove them gently when hot. I heat up until 180–200 degrees Celsius or 360–390 degrees Fahrenheit. Same with the cylinder to remove the sleeves. Even a little hotter when I have to remove the valve guides.

 

[ballbearian]

Did you know that there are two types of locking collars ?

Yes, and with that very fine thread, it is fun to guess which one it is.

I do heat up the whole cylinder head in my glass oven

I should have done that . An excellent idea.

 

[jensen]

I do heat up the whole cylinder head in my glass oven

I should have done that. An excellent idea.

Yes, but you need heat-resistant gloves, don't ask me how I know

 

[jensen]

During dinner, I did put the cylinder head in the glass oven and cooked it until done. I warm up the head slowly, so it will stay straight. It took 1 hour to get it to the set temperature of 250 degrees Celsius.

Did put the head on the two wooden blocks, so I could start the job, and for this job you need good tools



As long as you block the sprocket from turning (with the chain trick posted earlier), the chances are, that everything goes smooth, and in this case it went very smooth. I expected a fight, but with a few blows of my plastic mallet, the collar gave up and came loose.



Within 2 minutes, the nut came loose, and the camshaft slides out. The heat of the heat makes that the bearings are easier to move, so the camshaft cam out quickly.



The first bearing is out, and the second bearing has to go through the fitting of the first bearing, and as long as the head is hot, it's an easy job as well.



If you look closely, you can see the advance mechanism inside the sprocket. This one is ok, but unfortunately, I saw many destroyed with a hammer and a driver.



To get the other one out (in most cases, the second camshaft is the most difficult one), you have to secure the sprocket against the head to avoid damage on the sprocket.



To get this one out was the biggest issue, it was stuck. I did slide a very thin piece of steel from the inside against the camshaft, avoiding touching the advance mechanism. And after some persiference, the camshaft came out as well, without damaging the sprocket.



After this I thought I deserved a beer, a cold Belgian triple this time. Meanwhile, the head is cooling down, as the cams. The next job is to remove the bearings from the cams.



First, taking off the circlip that holds the point's cam in position, with the right tool this is easy.



The point's cam seems ok, but actual measurement has to be done in the near future.



For this kind of jobs, I have a very nice, small puller. Placing a soft stainless steel washer between the puller and the cam surface avoids damage to both.



Bearings were stubborn, and difficult to remove, I needed force to get some of them off.



But finally the bearings gave up, and the camshafts are ready for cleaning and inspection



I guess, that at 6 March 1989 the head is done by a PO, he wrote the date at the bottom of the head. I don't think that the bike did run long after that date, let's say 1 year, 1990. That means that the bike stood still 34 years.

 

[jensen]

Maybe you noticed, but in the last picture in the previous post, it's clearly to see that the PO used 2 different (intake) valves, this is the left side:



And this is the right side:



Time to take the valves out for further inspection, and with the rights tools, a piece of cake.



No need to compress further than this, any further than absolutely necessary can weaken the springs.



Much easier than the 450's, fewer parts, and self-cleaning valve by rotation. However, these valves are not in a good state anyway.



And after a few hours everything is ready for cleaning, inspection and measurement. I already have s set of bearings (6004-C3) for the rebuild. The rest of the parts have to be measured to decide if need to be replacement (except for the pistons, and the intake valves).

 

[ballbearian]

You had mentioned that the advancer was either new or very good. Does it still have it's rubber bumpers on the weight arms? I've never seen them and do know that it is hard to see them in their limit holes.

 

[jensen]

You had mentioned that the advancer was either new or very good. Does it still have it's rubber bumpers on the weight arms? I've never seen them and do know that it is hard to see them in their limit holes.

Yes, the advancer is good, but shows that something was terribly aligned. I'll explain later. And yes, the neoprene bumpers are in place

 

[ballbearian]

Yes, the advancer is good, but shows that something was terribly aligned. I'll explain later. And yes, the neoprene bumpers are in place

It has been advised to carefully check the swaged pins that hold the unit together for loosening.
I'm patiently enjoying your process and explanations.

 

[jensen]

First a picture of the good side, no damage or any wear pattern on the sprocket teeth, this is the reason I concluded that the sprocket seemed new or very good.



However, the other side looked totally different:



The only correct conclusion is that the cam sprocket, cam chain and crank sprocket weren't aligned properly, resulting in an asymmetrical wear pattern.

Looking more precise to the camshafts, is it noticeable that also two different camshaft styles are being used. One with oiling hole, and one without. Below the one with oiling hole at the lobe:



And one without oiling hole:



My preliminary conclusion is that this bike had an issue with one of the cylinders. More intensive cleaning of the piston will reveal this, or not. For some reason, the sprocket is replaced (despite the asymmetrical wear pattern, it seems to be a NOS replacement), but also one of the camshafts is replaced by a new one. The replaced valve, and the replaced camshaft are all at one side of the engine. The PO didn't align the sprocket well and after a poor rebuild (hence the pistons, hone job, and using the old rings) he / she didn't use the bike much anymore, or sold it.

Also, it's clearly to see that the exhaust valve of the cylinder with the wrong type intake valve is much hotter than its counterpart, all at the same side. Either that side was firing too early, resulting in overheating, taking the inlet valve down. Another, more suitable explanation is that one side didn't get not enough oil for a longer period, destroying the camshaft, and maybe taking the sprocket down as well. i will look very carefully into the oil gallery's and the crankshaft oil galleries after examining the inner side of the piston from that side.

Another anomaly is the that only one valve guide is worn, the others are in good / reasonable shape. The worn valve guide is located at the intake, also on the same side as the replaced camshaft and the wrong intake valve. On top of that, as showed in the beginning, two different spark plugs were used.

 

[jensen]

It has been advised to carefully check the swaged pins that hold the unit together for loosening.

In perfect order, tight and no movement noticeable.

 

[stl360+450]

Once the head is off, there is no easy way to hold the camshaft from turning to get the bold of the clamp mechanism from the clamp bolt at the tacho side. The easiest way I found is to use the cam-chain itself, works always like a charm.

Neat trick. Noted.

The advance mechanism, including the springs are build in the sprocket, thus if you have to replace the point shaft, or the advancer springs you have take the engine out, remove the top cover, etc.

If I were guessing based on appearance, I would think that this is one of the first automatic advance mechanisms ever devised.

No need to compress further than this, any further than absolutely necessary can weaken the springs.

Also noted. I went beyond that when I disassembled my XL350 head recently.

My preliminary conclusion is that this bike had an issue with one of the cylinders.

It's interesting to follow the trail of evidence sealed inside the motor for 30+ years. Are you able to say what model bike/motor the incorrect intake valve comes from?

 

[ballbearian]

Good analysis and guesswork. There was a change in the diameters of the points cam spindle of .5mm, IIRC, and since the right cam was changed, I wonder if they are correct.
The advancer could still be usable, even with the wear caused by improper set up of alignment.
I would think improper valve adjustment or even a broken spring could have cause the prior cam damage as well as an upper end oiling issue.

 

[jensen]

The next step is to split the crankcase, but before I can do that, I have to take off the clutch cover. It seems that the crankcase was never apart. After a few attempts, I only got 1 bolt out, the rest are now bathing is penetrating oil.

 

[jensen]

Finally, after 2,5 hours of fighting the bolt of the clutch cover, they gave up. Every bolt is saved, and after plating, reusable. It was clear that I',m the first one in the engine bottom, everything is just as the factory put it together, except that 31.000 km added a lot of junk. The oil spinner was never opened as well, I wonder how much crude can be found in there.

 

[stl360+450]

My first look at this spinner design. I suppose the total amount of material removed by the spinner can be completely exhausted when there is only enough room for the oil to pass down the middle?

A general question: is there any particular reason why some designs put the clutch and oil spinner on the left side as opposed to the right?

 

[jensen]

My first look at this spinner design. I suppose the total amount of material removed by the spinner can be completely exhausted when there is only enough room for the oil to pass down the middle?

That's why Honda states in their manuals to clean the spinner on a regular basis, and change the oil often. I'm going to switch over to Castrol 10W60 or equivalent (for example Motul), rebuild the oil pump (maybe going the Cappellini route, or the G-man route, depending on the amount of spare time I have), dismiss the spinning filter, add a two stage filter setup, and make it possible to add an oil cooler.

A general question: is there any particular reason why some designs put the clutch and oil spinner on the left side as opposed to the right?

Everything is different with this engine when it comes to the transmission. It makes me wonder how the engineering department of Honda worked, because in the same era of time, the CB92 is designed, which is a way more modern setup (transmission wise).

In the case of these ranges of engines (250-305) the spinner is situated on the L/H side, the dynamo (rotor & stator) on the R/H side, oil pump underneath the crank, driven from the crank center, primary chain drive, spinning filter driven by a chain, The secondary chain is situated on the right side, rear wheel brake actuator on the left side by a cable, brake pedal is on the right side. This bike is a whole other breed then the later 450's. The CB72 is a predecessor of the dreams, the 450's a predecessor of the CB92 technology (transmission wise). It was clearly visible that Honda had to find their way yet. Another reason is costs, the design of the 250-305 engines with the primary chain is probably cheaper than a gear driven clutch. Who knows what the engineers thought, designing this engine.....

In short, there is no particular reason to situate the spinner to the left side, it was more or less dictated by the setup of the transmission and the availability.

 

[jensen]

A close examination of the inner parts of the L/H side confirmed that I'm the first one that opens the bottom case and taking off the clutch cover. The bolts of the cover were never loose, that's why they were so stubborn. The bolts gave up after heating them one by one, using a large T-wrench with a modified JIS bit, penetrating oil, patience and perseverance. The crank nut was never chiseled to get loose, and no other damages were found.





Lots of discussion on forums where the shim on the spinner goes, but this picture shows how the factory designed it:



Clutch bolts are untouched too, another sign that no one was here before:



Chains everywhere. This is a late engine with a primary chain tensioner, my '61 engine hasn't one. It's also clear that the chain is stretched, or / and the sprockets are worn, too much slack which results in a noisy engine. Same for the oil spinner chain.



To loosen the clutch bolts and get the clutch inner off, I have to block the primary sprocket.



The inner clutch is secured with a set-ring, and with the right tool, a matter of seconds to take it off.