TexasAggie’s first bike build

Haven’t been able to work on it since, but after some research I’m thinking there’s a chance my chain isn’t perfectly tight. I used a protractor to find exactly where atdc +90 is, but I’ve seen that sometimes it’s a little past that and I noticed that and the point I marked one valve (right intake) is not quite as loose as the others. So when I do get a chance to open it back up, I’m going to try adjusting the cam chain first.


Sent from my iPhone using Tapatalk
 
Yes, though the tensioner is automatic once the lock bolt is loosened, if the cam is not in a position where it has no force being applied to it from one direction or the other, the tensioner may not be able to push enough to tighten both sides of the chain
 
Ok today’s the day I get this thing running.

I started out with adjusting the cam chain tensioner again. I went a little past 90 and insured all the valves were loose before opening it. It didn’t make a sound this time, but I opened it all the way and closed it anyways for good measure. Maybe the spring on it is weak? I did not replace the plunger.

Went and adjusted each valve one by one again, I’m pretty confident they are correct after this much practice.

Now I’m trying to kick it over and I can it to start and run as long as the right choke is on a, but it dies when I cut the right choke. Could it just be the right idle screw? Which wag do I turn it to open it up?

The sound is still there a little bit, but quieter. Having never heard one of these bikes in person it’s hard to tell if it sounds normal. If it can get it to idle w/o the choke I’ll try to shoot a video.


Sent from my iPhone using Tapatalk
 
Pulled the right side spark plug, it’s very fouled. Checked for spark, and it runs on one cylinder which probably explains why I can get it start still.
Plug is still sparking though so my ignition module hasn’t failed. I’m going to do some research.


Sent from my iPhone using Tapatalk
 
Ok, I know next to nothing about carburetors and throughout my past wrenching experience I’ve just unbolted then broken one set the idle and closed the hood.

Both these carbs came with the bike that was originally over bored. Probably either 66mm or 67mm so either 2mm or 3 mm over. The pistons I bought are 65 mm so 1mm over. The reason I mention this is because the displacement has been lowered but I’m not sure by how much. Both spark plugs have large amounts of carbon on the tips just from the small amount of running I’ve been able to pull off maybe 10 min total since Saturday. All I did was clean the float bowl before putting it back on and I’ve since adjusted the idle screw a bit but nothing else.

Is it likely that the jets are just dirty? Or do I need to go smaller for the smaller displacement engine. These are mikuni carbs but I’m honestly not sure which size. I’m pretty stuck at this point.


Sent from my iPhone using Tapatalk
 
Apparently Mikuni doesn't mark their carbs for size. Looks like you have to measure the throat of the carb at the narrowest spot.
I did come across this http://www.mikuni.com/pdf/vmmanual.pdf for tuning them
Stock Keihin carbs were 28mm so I think you'll be fine if the carbs are VM30's (30mm). 32's will probably give you flat spots from being over carbed.
 
Is it possible that a stuck float could be causing my symptoms? I know they were stuck down the first time I ran it because gas was pouring out the vents. Is it possible they got stuck up and now only let fuel by with the choke on? If I’m reading this right the choke bypasses the float bowl.
5df8dbea042157d43b1f353263847465.jpg



Sent from my iPhone using Tapatalk
 
Yes, the "choke" on a Mikuni is not like the conventional carb that blocks off air flow to draw more fuel into the cylinder, the Mikuni method is an enrichener as the diagram shows, drawing raw fuel right from the float bowl. If the enrichener works on that cylinder, it suggests the float bowl has fuel. It's possible your carbs need a cleaning - did the bike sit for a while with the current carbs on it?
 
ancientdad said:
Yes, the "choke" on a Mikuni is not like the conventional carb that blocks off air flow to draw more fuel into the cylinder, the Mikuni method is an enrichener as the diagram shows, drawing raw fuel right from the float bowl. If the enrichener works on that cylinder, it suggests the float bowl has fuel. It's possible your carbs need a cleaning - did the bike sit for a while with the current carbs on it?
Click to expand...

Yes, and the only cleaning I gave it was admittedly superficial.


Sent from my iPhone using Tapatalk
 
Anything is possible. If I was doing this I would be taking the carbs apart to inspect and clean. That way you can make notes of exactly what jets, slides, air bleeds, etc are in the carb for future reference. It will help in sorting out fuel issues when you know where you're starting from
 
LongDistanceRider said:
Anything is possible. If I was doing this I would be taking the carbs apart to inspect and clean. That way you can make notes of exactly what jets, slides, air bleeds, etc are in the carb for future reference. It will help in sorting out fuel issues when you know where you're starting from
Click to expand...

Yeah I think what’s next is to take them apart and more meticulously clean each jet now that I have a better understanding of the inside. When I first did it I was just trying to be extra cautious not to change anything because I didn’t know what I was looking at. Still not 100%, but trying is the only way to learn.


Sent from my iPhone using Tapatalk
 
Finally got time to start carb disassembly/cleaning. So far, things aren’t adding up.

I don’t have calipers, but using a tape measurer I’m getting 36mm at the top of the throat. That seems too big imo from what I’ve read.

First thing I’ve noticed, the jet needle is labeled 6DH7 which is not on the list for mikuni needle jets according to the tuning manual listed above. I see a 6DH3 for VM34s, but what I’ve got clearly reads 7.


Sent from my iPhone using Tapatalk
 
Just kidding, it’s a 32 I was measuring the wrong spot. It’s also labeled.
713f579315ef301439015ae0c9d53f54.jpg



Sent from my iPhone using Tapatalk
 
Update:
She runs! No starter plunger used at all (which after reading the manual I now realize I’ll probably never need in Texas). Clean carbs make a big difference and I learned a bit along the way.

https://imgur.com/a/SgYGxJl

A milder clatter sound present, but I think I isolated it to the pamco magnet having some play in it. It makes the same sound when you jiggle it back/forth.

Currently running very rich, I’m going to dial back the air jet and fix that. I have to take the left carb off to adjust it so it’s a slow process. First attempt I had the jet all the way open and it screamed to an idle of about 4500 rpm ha. These carbs are probably too big.


Sent from my iPhone using Tapatalk
 
First short test run was awesome!

Appreciate everybody on these forums that made this possible for me, riding something I rebuilt by hand was a really cool feeling.

This thread is probably done for a while, if I make any more improvements to the bike in the future I’ll revive it though. I’m thinking I’ll take it to that Honda mechanic I mentioned before to check everything I did, change the oil, check the valves and head bolts, but that’s about it for a while.


Sent from my iPhone using Tapatalk
 
TexasAggie said:
Appreciate everybody on these forums that made this possible for me, riding something I rebuilt by hand was a really cool feeling.
Click to expand...

It IS a good feeling, and we're glad you got there. Now about taking it to a Honda mechanic... as much as you've learned, you can learn to do that stuff too.
 
ancientdad said:
It IS a good feeling, and we're glad you got there. Now about taking it to a Honda mechanic... as much as you've learned, you can learn to do that stuff too.
Click to expand...

Haha I hear you, but I just want to get a second opinion before I go out on long rides. This is my first real bike and I don’t have any friends who ride, so I could’ve missed something that’s not obvious to me and I don’t want to find out the hard way. The mechanic’s not going to be the one who changes the oil and checks the valves/nuts though maybe my phrasing was off.


Sent from my iPhone using Tapatalk
 
TexasAggie said:
The mechanic’s not going to be the one who changes the oil and checks the valves/nuts though maybe my phrasing was off.
Click to expand...

Ah, that clears it up. Wondered why you would have done that after all the other stuff you'd already accomplished... (y)
 
ancientdad said:
Ah, that clears it up. Wondered why you would have done that after all the other stuff you'd already accomplished... (y)
Click to expand...

Read some yelp/google reviews on the mechanic... I think I’ll hold onto my money.

Can’t remember if it was this site or the old one but I’m pretty sure I read a quote from you about not second guessing your work and I think that’s good advice. I’ll keep my ears/eyes open to anything weird and just trust my work.
 
Resurrecting this thread for my new mission:
More than 20 min of sustained riding without idle problems.

Quick catch up since last post. No one else has worked on my bike but me. I’ve changed the fork oil and replaced the drain screws for the forks. I’ve changed the oil. I’ve switched from a faulty pamco to fresh points/condensers from 4into1 and in total put about 60 miles on it.

Today I’m testing the cheap battery I have. Surprisingly, it looks good. I charged it fully, it ended at 13.14. Let it sit for an hour and it dropped to 12.9 then turned on the high beams to remove surface charge and it dropped to 12.75. Another high beam test and it bounced from 12.15 with the lights on back to 12.75 with them off. It still isn’t a lot of AH, but it should at least run the bike when kick started.

I’m going to remove the coils now and test them, haven’t done that yet.
 
Good progress, and good that you're keeping your money. We can get you through pretty much anything here.
 
The main potential culprits I see are valves, coil, battery and regulator. I’m going to check the coils (just pulled them off last night but didn’t test them) and set the valve lash again before buying anything. I might buy a sparck moto even if one of the other 3 solves it though.

1. Valves- I checked them multiple times but I was never very confident about the values I was getting. I think the way I was holding the engine in place backed up some slack on the chain and could’ve affected the my adjustment. I was propping the wrench against a longer m6 screwed into the stator, but setting this pushed the crank back a degree or so. Do I have to set them at exactly tdc or can I set them anywhere they have max lash? Ie set the intake at the bottom of the power stroke and exhaust at the bottom of the fuel stroke so that I don’t need to hold the engine in place. My plan for now is to have a partner hold the wrench while I set the lash. Holding the wrench with one hand and setting the points seemed to work really well, but I won’t be able to do that on the right side.

Also the rattling noise that I assumed was the loose pamco magnet didn’t go away after switching to points so it must be from in the rocker box (I hope). I assume this is either because the valves aren’t set right, the cam/rockers are unevenly worn (I kept the originals and didn’t machine them kind of regret not at least asking the machine shop if they do that), or the used springs I bought aren’t to spec. I had the springs tested and they all performed within range of each other even though two were from a different bike so I kind of doubt that one. The valves are brand new and the seats were honed so I don’t thinking seating is an issue. We’ll see what happens after the latest lash adjustment.

2. Coils - These are the original blue Honda coils and as I mentioned I left one on for about 3 hours and who knows how often that happened since 1973. I’m looking for 4-6 ohms on each primary and consistent values (15k?) on the secondary. We’ll see.

3. Battery- It’s holding a healthy charge but that’s about all I have positive to say. It’s cheap, and motobatt is not... we’ll see how generous my better half is feeling.

4. Regulator/rectifier - I think I remember seeing a page in the fsm to test these with a multimeter, but perhaps it was just with their fancy “service tester” (which I really want to find for my collection now). I’ve pretty much convinced myself I’m buying a sparckmotto anyways and will probably pull the trigger randomly in the middle of the day without warning soon.
 
ancientdad said:
Good progress, and good that you're keeping your money. We can get you through pretty much anything here.
Click to expand...

Most of the mechanic stuff I was mentioning was just because this was the first road legal bike I had ever ridden and I didn’t even know if it felt right. Sure Texas said it was good to go, but Texas also green lit my Jeep that’s missing a floorboard, has an audible exhaust leak and 2% of the rear brakes.
I recently took my motorcycle safety course however, and it’s calmed my anxiety on that front. Particularly because the loaner bike I used for the course was a 97 Suzuki gn125 that while 24 years newer wasn’t technologically advanced from my bike... and had crappier handling and clutch control. That sufficiently boosted the confidence in my build.
 
Being off a couple degrees from TDC on valve adjusts is fine, I used a block of wood to hold a 3/8 drive breaker bar to keep it as close as possible.
it's possible that the coils are ok even though you left the ignition on, if the points were open for the coils then there was no completed circuit to fry them. Test to confirm.
Yes, scrap the original rectifier and regulator and get one of Matt's so you have consistent charging. Do this before replacing the battery and maybe you'll be able to hold of on the MotoBatt for a couple of months.
LOL, those MSF teaching bikes are pretty trashed most of the time. Operational? yes Mechanically sound? doubtful Road worthy? death sentence
 
LongDistanceRider said:
Being off a couple degrees from TDC on valve adjusts is fine, I used a block of wood to hold a 3/8 drive breaker bar to keep it as close as possible.
it's possible that the coils are ok even though you left the ignition on, if the points were open for the coils then there was no completed circuit to fry them. Test to confirm.
Yes, scrap the original rectifier and regulator and get one of Matt's so you have consistent charging. Do this before replacing the battery and maybe you'll be able to hold of on the MotoBatt for a couple of months.
LOL, those MSF teaching bikes are pretty trashed most of the time. Operational? yes Mechanically sound? doubtful Road worthy? death sentence
Click to expand...

Do you think the adjustment would still be accurate on alternate strokes then like I mentioned? Or does maximum lash not last quite as long as I’m thinking?
 
It has to be done at TDC, while the valve may feel loose at an alternate position you don't know if the rocker is still on the up/down ramp of the cam. If you could see the cam while doing the adjustment you could place it so the rocker was on the heel of the cam which is the highest lash/gap possible. But that's not possible on these engines.
 
LongDistanceRider said:
It has to be done at TDC, while the valve may feel loose at an alternate position you don't know if the rocker is still on the up/down ramp of the cam. If you could see the cam while doing the adjustment you could place it so the rocker was on the heel of the cam which is the highest lash/gap possible. But that's not possible on these engines.
Click to expand...

Gotcha, that makes sense.
 
Just tested the coils:

At first, both got consistent results. About ohms on the primary and 15k on the secondary. When I went to test the right coil a second time however, it bounced around before landing on 5. Concerned, I tested it 5 more times and each test it got worse and worse settling around 6 and jump frequently between 5-40 ohms. After a little googling, I tried testing it while moving it/tapping it and sure enough this caused huge spikes. Same test on the left coil had no effect, it stayed consistently at 5 ohms. I think I can definitely say the right coil is no good, and the fact that it sometimes works in range is probably why it looks it works at all. I’m going to start shopping for two new ones and replace as a pair. So far I’ve found some replicas from Niche cycle that seem like solid deals at $24 a piece.
 
4into1 has a pair plus caps for $57.80. That’s probably the one I’ll go with. They look exactly like the niche cycle one too.
 
Confirmed the regulator is essentially functionless as well. 300-500 ohm resistance in both directions instead of the 5-40 the normal direction and 600+ reverse as outlined here:
d549e7e9c9adeea8b1d96fce2b3d9fd2.jpg

Sparckmoto got a VHT discount code?[emoji51]
 
4into1 was out so I ended up going with the niche cycle ones anyways. My spark plug boots were new so I’m just going to reuse them. They’re the same 5k ohm ones June’s got pictured.
 
My Sparck moto came in today! Question for someone who has installed one or Matthew (I know I’ve seen his logo on an avatar on this site):

The sparck moto replaces both the regulator and the rectifier, but the harness has two fewer wires (one less green and yellow). Is that because they are redundant? I’m seeing a wiring diagram show the same yellow go to both and green is ground so I’m assuming that’s the case. Do I need to take any special pre-caution on the now open yellow wire? I was just going to tape it.
Also, I’ve seen somewhere (it might’ve been those guys in Houston so I’m questioning it) that the alternator works in two phases with phase two only kicking on if the lights are on. FSM seems to corroborate this with daytime/nighttime expected charging levels. Does this unit change that or does the wiring for that happen only at the alternator?
 
Unless you have non standard wiring, the new reg/rec will plug right in to the old connector. Pull the loose black wire out of the sleeve and plug it into the vacant black connector left when you remove the old regulator. The two loose wires left after removing the reg should be taped up as I believe they are both hot. Green is ground so maybe it's just the yellow if indeed that's what's left.

I'd also add that the "full charging mod" is done in the headlamp shell and is simply removing the headlight switch from the charging circuit. I don't remember the exact wires you'll touch but it's as simple as disconnecting a couple of wires and connecting them elsewhere; you should be able to find better info with a quick search.
 
briandel said:
Unless you have non standard wiring, the new reg/rec will plug right in to the old connector. Pull the loose black wire out of the sleeve and plug it into the vacant black connector left when you remove the old regulator. The two loose wires left after removing the reg should be taped up as I believe they are both hot. Green is ground so maybe it's just the yellow if indeed that's what's left.

I'd also add that the "full charging mod" is done in the headlamp shell and is simply removing the headlight switch from the charging circuit. I don't remember the exact wires you'll touch but it's as simple as disconnecting a couple of wires and connecting them elsewhere; you should be able to find better info with a quick search.
Click to expand...

Sounds good.
I was mostly just curious if it’s a mod that’s even necessary now that the regulator/rectifier is modern
 
Ah, yeah I think you'll still want to do it. The new reg/rec won't change that you're only charging at 50% when the high beam is off.
 
80e3e0ebea7caae0013a39069b81faef.jpg

Here’s my installation, it’s where the regulator was and since the holes don’t line up I slipped a zip tie in inside slot. Feels tight and should last a while being out of the sun.
 
If you're running the stock battery size you could wait to see how your riding style might affect the overall charge rate. If you're up in the revs enough most of the time you probably wouldn't need it, but if you do a lot of traffic commuting at lower average revs for some part of the ride, it might behoove you to bypass the headlight switch to get max charge all the time when above 2500 or so. The mod is to connect the yellow from the main harness with the white that has a yellow colored half on the female connector cover (sometimes referred to as a yellow tube) also from the main harness, effectively eliminating the loop up into the headlight switch and "turning on" the extra alternator output all the time.

This diagram
 
briandel said:
Ah, yeah I think you'll still want to do it. The new reg/rec won't change that you're only charging at 50% when the high beam is off.
Click to expand...

To be accurate, it isn't just the high beam, it's the headlight itself no matter which beam is on. And, not that it matters much, but I think it's about 33% more (2 additional alternator coils added out of the 6 total)
 
TexasAggie said:
So you did it on your bike and no consequences?
Click to expand...
None so far. I'll let others chime in but I'm pretty sure it's a no brainer with no adverse effects (battery life, etc.). No wires are cut/spliced so it's completely reversible if ever need be.

As for reg/rec installation, I put mine in the same spot but enlarged/lenthened the holes with a Dremel so I could secure it with both bolts. Matt from SparckMoto says he just throws one bolt in there so I'm sure you'll be fine. Might want to put some blue lock tite on it for peace of mind.
 
ancientdad said:
To be accurate, it isn't just the high beam, it's the headlight itself no matter which beam is on. And, not that it matters much, but I think it's about 33% more (2 additional alternator coils added out of the 6 total)
Click to expand...
I see that now on the wiring diagram; thanks for the clarification. I don't understand why this "mod" is a thing then since I'm pretty sure it's required to have your headlight on while riding anyways (in the US at least...)

fa8b9fdea47db17224b2066482a60ff0.jpg


EDIT: I guess it's a state by state thing... Might spend some more time on this site tonight: https://www.motorcyclelegalfoundation.com/state-by-state-guide-to-motorcycle-laws/
 
I did the mod and added the Sparkmoto unit. Seems to work just fine and fixed my overcharging issues with the old regulator.
 
briandel said:
I see that now on the wiring diagram; thanks for the clarification. I don't understand why this "mod" is a thing then since I'm pretty sure it's required to have your headlight on while riding anyways (in the US at least...)

EDIT: I guess it's a state by state thing... Might spend some more time on this site tonight: https://www.motorcyclelegalfoundation.com/state-by-state-guide-to-motorcycle-laws/
Click to expand...

Actually, remember that these bikes were built and sold here before it became a universal law in most states that the headlight be on full time, which is why Honda changed the right hand switch on all models later on so there's no on/off switch for the headlight and the starter is the only thing that interrupts the headlight being on, then returns it to on after the starter button is released. All the 360s and the 500T in our category are equipped with no on/off for the headlight on the right switch, and probably the SOHC 400/450 series that came out in '78
 
ancientdad said:
Actually, remember that these bikes were built and sold here before it became a universal law in most states that the headlight be on full time, which is why Honda changed the right hand switch on all models later on so there's no on/off switch for the headlight and the starter is the only thing that interrupts the headlight being on, then returns it to on after the starter button is released. All the 360s and the 500T in our category are equipped with no on/off for the headlight on the right switch, and probably the SOHC 400/450 series that came out in '78
Click to expand...

That’s what I remember reading, and I think ‘73 was the last year.
It makes sense given the inherent charging issues and weak batteries back then that you’d probably take your short trips with the lights off.
 
You must log in or register to reply here.
Back
Top Bottom