CM200 drive lash

[FBSF]

No, no, not out on the lash after a drive on the CM... although a stiff one to settle my nerves after a ride is becoming more the order of the day!

There's a big amount of play on the output shaft - it'll turn a good 30-40 degrees when in gear - meaning slow riding in traffic is getting horribly snatchy.

I originally thought it was chain tension or cush drive, but all seem correct - it's definitely inside the gearbox. The bike has about 23k on it.

Anyone come across something similar - is it likely to be a single cog that can be replaced or is the whole gearbox on old faithful about to die....and should I be wary of riding it?

Cheers, FatboySlimfast.

[Suntan Sid]

How are you getting the 30-40 degrees movement?
Are you measuring this at the output shaft or at the rear wheel?
Are you sure the sprocket isn't moving around on the splines?
Whether your front sprocket has a locking plate, or a big nut and tab washer, are you sure they're secured correctly?
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"Everybody needs money, that's why they call it money!"

[FBSF]

Hi Sid,

It's the output shaft that's moving even when in gear.

The sprocket is firmly attached to the splines (that was my first thought), but when the sprocket moves, so does the shaft.

This is what is concerning me - it's definitely something within the engine casings that has the play in it - I was hoping that the engine had a primary drive chain that had become slack, but it's all gears inside, looking at the manual.

[Suntan Sid]

I don't know a lot about gearboxes.
If a spline or tooth, within the gearbox, was worn or snapped, would that give constant freeplay, or just freeplay when the gears were in a certain position?
Is the clutch correctly adjusted, slipping at all, has the center locking nut come loose?
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"Everybody needs money, that's why they call it money!"

[Teflon-Mike]

OK, so you take hold of the drive sprocket, engine 'off' and twist, and it can turn, what, 1/8th of a turn....
Fact it only turned 1/8th of a rev would make me think "Ah! Its in gear" or it ought to KEEP turning.... forgive the egg-sucking 'basics' here, but worth going through them.. SO Next Question, What gear s it in? 1st?
I don't have the book for the 200, so don't know what the reduction ratio's are for each of its 4 'gears'....
On the 5-speeds, I do have a book for, you have about 3:1 reduction on the primary drive between the crank shaft and clutch, then almost another 3:1 Reduction on 1st gear..
SO, 1/8th turn at the out-put shaft should cause only 1/24th of a turn at the input shaft, and 1/72th of a turn at the crank-shaft... about 5-Degrees..... There's nothing 'locking' that shaft apart from the compression on the piston, and until you get one to TDC on the compression stroke, that will be bugger all, and even when you get there, 5Deg is still bugger-all, at TDC against compression... your 1/8th turn at the sprocket may just be the 'take up' of compression before you feel 'significant' resistance on the shaft.

NB... your 'test' isn't necessarily telling you much, if anything at all.

You could try it again in 4th, which probably only has 1:1 reduction to the clutch, you should get 1/3 the movement, but, still subject to your 'feel', and you still have no idea where any lash maybe....

IF there is any lash in that transmission, my 'bet' would be its in the clutch.

Drive is being transited through the 'tangs' on 8 fibre plates in the slots of the clutch basket, they have to be free to slide in, so have to be a pretty 'sloppy' fit to begin with, and the 'softest' bot of the transmission, compared to case hardened steel the place most 'wear' is likely to happen fastest...

BUT, you wont know without pulling the primary cover and having a much closer inspection of stuff, and being able to actually lock shafts to see where any 'real' lash may be.

As described, you have't rung any alarm bells; you may not have a real problem; It's likely if there's fault, it could still be in your Chain & Sprockets, your cush drive bushes, your back wheel spindle clamping, even the rear wheel bearings, the swing-arm (known to go a it wobby when they rot) the swing arm bushes, and even the engine mountings! and you have just jumped on something that just 'looks' like it could be a fault that isn't!

I'd do a LOT more proper investigatory before pulling the motor; and I wouldn't be looking at the engine too soon, I'd be eliminating the back end and ALL sources of 'slop' and then, before blaming cogs, I'd be looking at the clutch.

If that helps any.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[FBSF]

It's a good point - if something was broken, it'd be intermittant, whereas it does it all the time. The clutch isn't slipping, but I don't think that would be it - the movement causing the issue is really free - i.e. no resistance at all, not like it would be if the clutch was slipping a bit.

I don't think the CM has a locking nut for the clutch - it has a circlip on the clutch basket to keep it in. Diagram is below.

https://www.cmsnl.com/honda-cm200t-twinstar-1982-usa_model7281/partslist/E++07.html#results

I might drop the oil out and take the cllutch cover off and see if I can find any movement by holding the clutch basket (by hand) and then trying to move the gearbox sprocket...

[Teflon-Mike]

I'm pretty familiar with small honda clutches, ta... too familiar!
SLIP has nothing to do with the issue.
Plates might well be gripping quite nicely. When 'engaged'.
Drive is transmitted through the clutch plates by the 'tangs' on the edges of the plates that key them into the basket. Look at your diagram.
If those tangs have been worn, it wont stop the faces of the plates sticking together, will it?
Meanwhile you are obtudely sticking you your theory t HAS t be something IN the engine!
Do yourself a favour. while you have the sproket cover off, go check the two rear egine mountig bolts! Try waggling the engine in the frame.
NEXT, and another good bet, do yourself another favour, take the front engine plate off the down tube and engine.
There is a VERY good chace that over the years that has collected a full load of 'crud' and rotted, if ot the bracket, then the botto of the down tube, and any 'weakness' will let the whole engine 'rock' on load change, vibration loosening off other engine mountig bolts, and you clonking isn't IN the engine, its the whole chuffin engine!
SWING ARM, again, prone to collect crud around the pivot and in the brace between the two arms. Metal goes thin and weak, and swing arm pivots wear out, ad the whole back end slops about. And under load changes from the engine, the tension on the drive chain changes as the swing arm 'shfts' or flexes.
OR, the fish-plates where the spindle clamps up, they rust under the washers, leaving ridges, and when you adjust the chain, and tighten it back up in a new position, vibration shakes it loose, and let it shift.
Wheel bearings! More chance of slop. They wear. And under load change the hub can wiggle about.
Metalastic drive cushes i the hub; still can add to that.
You have not eliminated anywhere NEAR enough possible sources of plain 'slop' to be blaming anything 'in' the engine yet!
Go check the engine mountings properly.
Go check the swing arm properly.
THEN, you might return to the engine, and apply similar 'logic' to work through the problem LOGICALLY
Randomly guessing that the 'problem' might e in the gearbox, and then RANDOMLY dismissing the clutch, because it doesn't 'slip' is NOT working LOGICALLY, ad working 'random' its random chance whether you will fix ANYTHING!
GO CHECK THE BASICS!
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[FBSF]

There's a lot of things there to check. And check them I will.

The reason I was leaning to something internal (by which I meant not sprocket or towards the wheel from there) was that sometimes if I have to accelerate quickly, I get a big juddering vibration which goes away if I then throttle off for a short while.

Which, looking at what you've said, may well be the clutch. It's had new friction plates, but I haven't changed the plain plates. Another thing to check.

P.s. my last response was written whilst you were writing yours - I was responding to Sid's as I hadn't seen yours at that point. I wasn't questioning your knowledge - any input is welcomed.

[Teflon-Mike]

You are still trying to make connections between 'effect' you observe, and 'cause' you are purely guessing at.
STOP IT. this is where things go wrong.
Don't guess, it CHECK it.

You have 'judder' and 'clonk'. force that makes stuff move comes from the piston top, and goes all the way through to the back wheel, it could be ANYTHING 'in' that train that is supposed to move, or 'around' that chain, that isn't supposed to move.

You have to start at one end of the train, and work through it all, eliminating or confirming an issue' and not even assume that discovery of a 'single' issue' will be the sole cause of the effect... it usually isn't; two or more 'issues' compound each other to create the effect; so you keep going until you have eliminated all possible issues and identified as many actual issues as there may be, and fixed them ALL to make the effect go away.

Sorry for any excess frustration displayed in cross comms; but it's a lost Lesson in mechanics that infuriates me.

Far too many think, its all 'expert know-how', and a expert would know what to do; thinking that 'what to do' would be 'what to do.. to put it right'.. fault-find by ESP, NOT know what to do.. to FIND the problem, BEFORE they know what to do to put it to rights!

An awful large chunk of that 'expert know-how' isn't having seen problems before, its simply knowing that you have to work logically ad methodically, to FIND the problems. ALL the problems, to put them to rights.

And any one with half an ounce of common cocum, ought to be able to do that, and fix the problem.. in the end. They may just have to spend a bit more time working out all the possible issues, and more still eliminating the ones that aren't. But they'll still get there. Just time and effort, the 'expert' put in to get their 'expertise' in the first place, that so many don't want to to put in these days, hoping 'google' will give it them instead!
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Petemate]

My bike, too, is suffering from some slack in the transmission of power to the rear wheel. The bike is a recently 'restored' (lol) LA250 Custom, same engine as the North American CM250C, some Rebels, 250 Nighthawk, 233cc CB250 and CD250U among others, and very similar to the CM/CD200. I will brave the cold tomorrow and do what I have been promising myself for weeks now, well, since putting the bike back on the road in April, and that is put it on the centre stand and confirm what I think is the culprit, ie rear cush drive bushes. I know the clutch components are all OK, ie no play in the splines of either the shafts or the tongues of the plates, and no play whatever at the front sprocket and its attachment. As advised, check thoroughly, IMHO first from the rear starting with those dreaded cush drive silent(!)blocs. I would respectfully suggest that there is less likelihood of serious internal engine problems.
My bike's symptom is a noticeable clunk each time I feed in the drive from a pulling away. This does not occur when I have slowed down gently, ie not with hard over-run as in down changes with the resultant opposing load in the transmission (by transmission I mean everything from the clutch basket gear teeth to the rear wheel and its components), but when I have gone down through the gears and come to rest in traffic then into 1st gear and pull away again- clunk. The symptom has not got any worse from when I put the bike back on the road, though I had not ridden it before purchase and strip down. During the resto, I replaced the pair of 3rd gear wheels as there were a couple of teeth missing from one of them. The remainder of the transmission appeared to be in good condition, and I only have a very faint whine in 4th which I am putting down to bad luck/general wear as there were no chips or scratches on any of the gears noticed before reassembly. I have to assume that my clunk is not within the transmission as the caning I have given this poor little beast since recommissioning would by now have mashed up the innards completely!
I will report back tomorrow after the promised check.
Good luck OP in identifying the cause.
Pete

PS excellent advice from Teflon-Mike.
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82 not out....1983 Honda LA250 Custom
2008 Saab 9-3 1.9 Tid 150 Vector Sport estate
2005 Stirling Eccles Topaz 2-berth

[Petemate]

Can't find any obvious signs of slack in the cush drive bushes, so tomorrow I'll have a closer look at the front sprocket. Hmm. Mystery. I do know for sure that the clutch centre is OK; my model has a nut rather than the circlip that some of these engines have, and it is definitely torqued up correctly. I have had it apart and replaced the clutch plates since putting it on the road due to having the wrong oil in originally (don't ask.... doh) and I know the shaft and hub splines are perfect.

Too cold & windy to go out & check it today and anyway have pain in my right wrist following a cortisone injection in the carpal tunnel. Ouch.
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82 not out....1983 Honda LA250 Custom
2008 Saab 9-3 1.9 Tid 150 Vector Sport estate
2005 Stirling Eccles Topaz 2-berth