1977 CB200

One thing I did notice is that the tickover rises a bit (from 1,500 to 2,500RPM) after a couple of minutes, and I also noticed a little bit of fuel (drops) overflowing from the left hand float bowl. Here is my thesis: the left hand float or valve is allowing the bowl to flood very slightly at tickover - so after a few minutes it fills up, richens the mixture on that side and so increases the engine speed. Does that sound plausible?

I could just bend the float tab up a bit to lower the float, but the carburettors will have to come off anyway, so I might as well fit the reconditioning kits I have.

:)
 
Othen said:
One thing I did notice is that the tickover rises a bit (from 1,500 to 2,500RPM) after a couple of minutes, and I also noticed a little bit of fuel (drops) overflowing from the left hand float bowl. Here is my thesis: the left hand float or valve is allowing the bowl to flood very slightly at tickover - so after a few minutes it fills up, richens the mixture on that side and so increases the engine speed. Does that sound plausible?
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I'm not the best carb guy to ask, but I can tell you that slight imbalances in both idle speed adjustment between carbs as well as slight differences in mixture screw adjustments can often allow a change from cold to warm.
Othen said:
so I might as well fit the reconditioning kits I have.
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Minus the jets, and possibly the float needles if they aren't exact matches in every way, because kit parts accuracy is always suspect.
 
ancientdad said:
I'm not the best carb guy to ask, but I can tell you that slight imbalances in both idle speed adjustment between carbs as well as slight differences in mixture screw adjustments can often allow a change from cold to warm.

Minus the jets, and possibly the float needles if they aren't exact matches in every way, because kit parts accuracy is always suspect.
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Noted - I saw your note previously.

:)
 
NeverEverJamToday said:
Did you replace the old o rings on the intake manifolds?
If they are old flat and hardened instability can arise as the engine warms.
Also had to break out the English to English dictionary for "shooftie".
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My apologies for using such and Englishism, normally I remember to include the American version as well (silencer/muffler and so on), but I’d forgotten that ‘shooftie’ might not cross the Atlantic easily.

:)

Addendum: O rings? I’ll have a look when I take the carburettors off.
 
Whilst investigating that increase in engine speed I noticed the right hand cylinder was hardly getting warm - but if I pulled the plug lead off the engine died, so it was producing some power - but not much and hardly warming. It couldn’t be an ignition problem (good, strong spark both sides and static timing spot on), and it didn’t seem to be mechanical (same pressure in both cylinders - 90psi, but that was because I was using a car compression tester with a long whippy lead) so it had to be fuelling. I noticed that winding the stop screw in virtually all the way on the right cylinder did make the engine speed increase, but the result was erratic. The issue had to be an almost blocked pilot jet on the right carburettor.

The carburettors would have to come off again anyway, so I decided to rebuild both with the kits I had. A couple of hours later it is all back together and that fuelling problem is solved:

IMG_6664 by Alan Othen, on Flickr

The kits were pretty comprehensive, everything fitted perfectly and new O rings to the manifolds were included.

It is still a bit noisier than I’d like, but otherwise it seems to be running well: ticking over reliably at 1,200RPM, good reaction to the throttle and then settles down again quickly. Apart from the mechanical noise (better than it was I think) I’m almost there.

I do have a very slight fuel overflow, this time from the right hand carburettor - maybe the new float valve will bed itself in?

Alan :)
 
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Ancientdad was spot on about the float needles in the refurbishment kit - I couldn’t solve the slight overflowing issues (both sides) so I swapped back to the original float needles (with the replacement seats) and that fixed the problem.

The CB200 is running well now - I did a few circuits of our residential estate and everything was very nice. It is still a bit noisy, but I can’t find anything wrong so perhaps I’ll give it a good ignoring.

The only remaining substantial job will be routing the control wiring through the handlebars. I’ll try to get that little job done next week.

Many thanks for your help chaps - that one has taken 2 1/2 years (but that did include a house move).

Alan :)
 
Othen said:
Ancientdad was spot on about the float needles in the refurbishment kit
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Just dispensing information learned from others far more familiar, but I'm glad it helped you solve the problem. When a carb-knowledgeable individual like Mike Nixon says it, I'd suspect it to be true. Honestly, I've had my share of disappointments with kit parts even a few decades ago (missing pieces, incorrect gaskets and/or o-rings) so with time it seems to have only gotten worse.
 
ancientdad said:
Just dispensing information learned from others far more familiar, but I'm glad it helped you solve the problem. When a carb-knowledgeable individual like Mike Nixon says it, I'd suspect it to be true. Honestly, I've had my share of disappointments with kit parts even a few decades ago (missing pieces, incorrect gaskets and/or o-rings) so with time it seems to have only gotten worse.
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Many thanks - you called it just right - which saved me hours of head scratching. I also used the original float chamber gaskets as the replacements weren’t a very good fit.

:)
 
This is just me thinking aloud chaps - but I’d certainly appreciate some thoughts about whether I’m barking up the wrong tree.

The CB200 is now starting easily, ticks over (still a little lumpy) but is still noisier than I think it should be. I’ve had the top end apart twice: once to replace the barrels and pistons, then again to change the cam chain and I can’t find anything mechanically wrong.

Now, remember this engine had been butchered in the past (probably decades ago) when it was bored out to 240cc (hence changing the pistons and barrels back to standard items), also remember that a few weeks ago I checked the compression and got an identical 90psi in each cylinder. At the time I put that down to me using a car compression tester with a long hose that had a significant volume compared with the compressed volume of each cylinder, but what if that wasn’t the explanation.

Okay so far? How about this hypothesis: when the motor was running at 240cc the head became distorted in the area between the two cylinders, such that even a new gasket has been unable to effectively seal between the two combustion chambers. It is a 360 degree twin, so a compression test would see one cylinder on its power stroke at TDC, the other at the end of its exhaust stroke. Could this lead to it reporting 90psi on both cylinders (yes, of course it could)? furthermore could it account for the noisy and slightly lumpy running? I don’t know, I’ve never come across this on an air cooled engine - but I’m hoping one of you chaps has some experience of something similar.

I could try just re-torquing the head, which might help, but I‘ve had similar noisy running after both times the motor has been apart, so perhaps that wouldn’t work. I could do a leak down test with the cylinders close to TDC and see if I get some air coming out of the opposite side exhaust. Any other ideas?

If it does turn out to be some distortion in the head (I didn’t particularly check the head, apart from a petrol leak test on the exhaust valves because I don’t suspect anything was amiss) then can these heads be skimmed? Are thicker gaskets available?

I’m running out of ideas to explain this pesky noise - any ideas would be well received.

Alan :)
 
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… further to the above. I’ve found and purchased a used cylinder head for £45, it looks to be in quite good condition from the photos. My plan is to check it off the motorcycle, and then swap it over with the cam/tachometer drive/ignition from the old head. Is this a sensible plan? I don’t know, but I don’t have any other ideas, and it is a low risk strategy in that £45 isn’t much money and if it turns out I don’t need it I’m sure I’ll be able to sell it on.

In the meantime I’ll get the handlebar switched routed properly and the wiring tidied up this week.

This CB200 has proven to be a challenge!

Alan :)
 
You would have to take off the tach cover and look straight at it, preferably moving the crank with the kickstarter by hand to see if there is any movement of the cover. It's possible to assemble misaligned, where it will run but not quite right. The easiest way to identify this is the case is if the kickstarter is harder to move than expected by hand due to friction on the camshaft. Think this issue was mentioned in a very long cb200 post on "the other site" where improvements were documented. This scenario has happened twice to me when reassembling, and it wasn't due to improper valve timing.
 
NeverEverJamToday said:
You would have to take off the tach cover and look straight at it, preferably moving the crank with the kickstarter by hand to see if there is any movement of the cover. It's possible to assemble misaligned, where it will run but not quite right. The easiest way to identify this is the case is if the kickstarter is harder to move than expected by hand due to friction on the camshaft. Think this issue was mentioned in a very long cb200 post on "the other site" where improvements were documented. This scenario has happened twice to me when reassembling, and it wasn't due to improper valve timing.
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Tach drive not engaged? That's the only other thing I can think of would cause it.
 
Hi again chaps,
I wasn’t doing anything else this lovely Saturday evening, apart from watching Motorcycle Rewind videos on YouTube, so I popped out to the garage for a quick shufi:

IMG_0654 by Alan Othen, on Flickr

… everything looks straight and level, I checked the JIS screws were tight.

I‘ve run out of ideas… hence the thought of swapping the head :)
 
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@Othen When you put your head gasket on, did you make sure to verify you aligned it based on the position of the cylinder seals, not the bolts? The repro gaskets I have purchased have all been stamped incorrectly, requiring filing out the bolt/oil channel holes to make the cylinder seals align correctly.
 
NeverEverJamToday said:
@Othen When you put your head gasket on, did you make sure to verify you aligned it based on the position of the cylinder seals, not the bolts? The repro gaskets I have purchased have all been stamped incorrectly, requiring filing out the bolt/oil channel holes to make the cylinder seals align correctly.
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Not at all. I used one of the new gaskets supplied by the PO in the parts box, aftermarket but I think from DSS. I don‘t remember it saying anything about having to file the gasket for it to fit in the manual.

When the new head arrives I can check carefully on the bench, and when I’m happy with it swap everything over.

:)
 
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ancientdad said:
Tach drive not engaged? That's the only other thing I can think of would cause it.
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Do you think it would be worthwhile to just take the tachometer drive, back to the right cylinder head cover off, then refit it taking careful attention to the drive being properly engaged on the camshaft?

Alan :)
 
NeverEverJamToday said:
Is your right side cylinder head cover (#21 in the manual,p13) installed flush and straight?
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… as I asked Ancientdad in the post above, would there be merit in stripping the tachometer drive back to the cylinder head cover, and then refit-fitting it from scratch, taking care to make sure it is fitted correctly?

Alan :)
 
If the tachometer is working properly then the drive is assembled correctly, and if the gasket is sealing at the tach drive/cam bearing cover and the head then it would seem to be seated on the head correctly. If you do decide to remove the cam bearing cover, you would need to do some prep first - take all valve covers off, rotate the engine to a point where at least both valves on the right cylinder are closed fully, then loosen both valve adjustments on the right cylinder to as loose as possible before tach drive/cam bearing removal.
 
ancientdad said:
If the tachometer is working properly then the drive is assembled correctly, and if the gasket is sealing at the tach drive/cam bearing cover and the head then it would seem to be seated on the head correctly. If you do decide to remove the cam bearing cover, you would need to do some prep first - take all valve covers off, rotate the engine to a point where at least both valves on the right cylinder are closed fully, then loosen both valve adjustments on the right cylinder to as loose as possible before tach drive/cam bearing removal.
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Understood. In that case maybe leave it.

I‘m working on routing the switchgear wires correctly, which is proving to be more of a job than I’d anticipated because if all the things a PO has bodged that I’m putting right as I go. Report to follow in the next few days.

Alan :)
 
What appeared to be a simple little job: routing the control wires through the handlebars, ended up being very involved - but only because I spent a lot of time correcting a PO‘s bodges.

The project started off well: on Sunday I found a set of serviceable (rather than very good) handlebars from a Honda CB at an autojumble, complete with the holes to route the wires through - and including the left side switches, clutch perch and wiring already installed. I scrubbed off the surface rust and gave the handlebars a coat or two of some ’chrome’ aerosol paint I happened to have in the garage, ready to start on Monday (yesterday).

A little reconnaissance showed that a PO had butchered the bike a great deal: the kill switch didn’t work, neither did the horn and the wiring was all over the place - with some horrible domestic connectors here and there. Here is an example: inside the right hand switch a PO had cut the wires for the kill switch completely, leaving about 5mm stubs on both:

IMG_6718 by Alan Othen, on Flickr

… I have no idea why. I found the remnants of the two wires joined together with a household connector where they emerged from the loom about 6” away. So, the first job was to disassemble the right hand switch (taking care not to lose that little ball bearing), solder on some tails for the kill switch, reassemble everything and repair the loom with proper shrink trunking. At that point I could pull the right side loom through the replacement handlebars.

Roger so far? The left side was much easier because remember the new ‘bars came with the switch and wiring. I tested the switches both sides with a multi meter and everything worked as it should. The next job was reconciling the wiring in the headlamp bowl, under the tank and for the horn (Which had never worked in my tenure) The last PO to work on the motorcycle clearly had no electrical knowledge, and had left a few things disconnected where he/she couldn’t work out where they went. Nothing is very complex on these little bikes though, so I soon had everything working and tidied up considerably. The horn worked - it had just been wired up wrongly.

Close to the end of the day I felt quite pleased with myself: the wiring was correctly installed, loads of mistakes were fixed, the connectors were reconciled and the motorcycle reassembled. I had linked up the clutch cable using the perch that came with the autojumble bars, and tried it out half a dozen times whilst adjusting it: the perch then cracked through and through: it had looked fine, but had obviously been stuck together with Liquid Metal or something similar. Ho hum.

There is no point getting cross about things like this, I’m pretty sure the autojumble seller had no idea of the issue. I had to provide a clutch perch, so the answer was to make up a hybrid switch with the replacement top half (turn signals) still attached to most of the wiring and staying on the bike, and the original bottom half (the perch and horn switch) being swapped in place. This involved just one soldered joint (for the horn) and the provision of a frame earth return (it obviously wasn’t a CB200 switch, but that doesn’t really matter).

I‘m pleased to report that everything worked fine the second time of asking: now the kill switch and horn both work fine - as do all the lights:

IMG_6725 by Alan Othen, on Flickr

The handlebars are more or less correct. The switches are Honda CB, but not from a 200, and work just fine.

It is quite satisfying to get a job sorted out the way it should be; this one was a bit fiddly, but didn’t cost anything apart from a tenner for the handlebars and quite a bit of my time. The CB200 looks really smart now, and works fine apart from that mysteriously noisy motor:

IMG_6724 by Alan Othen, on Flickr

… I have run out of ideas regarding what might be wrong. I’ll have a secondhand head here in a day or so. When that comes I’ll check it out and then delve into the engine again: check the head gasket, tachometer drive and anything else I can think of :) .
 
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