Clutching at Straws.

Camel, Sahara, Kanguro, Coguaro
Butch
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Joined: 15 Oct 2016 16:47
Location: Essex
Location: Mid Essex

Clutching at Straws.

Post by Butch »

Thought I’d start a new thread for my continuing issue, namely my draggy clutch. To recap on the story;

This was an issue when I bought the bike. Simple enough to fix … I thought.
Had problems in my initial strip down as a couple of compression nuts were overtightened and locked solid.
After some slightly destructive disassembly I then found the plates heavily oil contaminated.
Ordered and fitted oil seals, friction plates and replacements for the two cups and nuts I’d had to butcher.

The clutch was still draggy.

I’ve since fitted new plain plates and also experimented with and without the dish plain plate in the stack.
It also has a new cable and I’ve checked operating arm angles etc.
I’ve probably been in and out of that clutch a half dozen times now – it is at least easy after that first strip.

The clutch is at least as draggy now as when I bought it.
It is quite heavy at the lever.
The pack expands as the bike warms to the extent that the lever will come half way back the bars by this time – I have to adjust the slack out on the fly.

I’m sick of it. What trick have I missed?

Thanks
Last edited by Butch on 31 Jul 2017 07:54, edited 1 time in total.
'It must be a .....'
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Joined: 12 Sep 2010 12:25

Re: Clutching as Straws.

Post by 'It must be a .....' »

Hi, could there be a problem with clutch push rod/s length; someone added a ball bearing etc which would mess things up at the operating lever end? I've got an engine apart at the moment so I'll get back to you with measurements, Ian
'It must be a .....'
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Re: Clutching as Straws.

Post by 'It must be a .....' »

Hello again,
Clutch operating (release) rod is 30mm long and a diameter of 7mm
Two clutch release rods both 89mm long with a diameter of just under 5mm
Clutch operating 'mushroom' 50mm long and again with a diameter of just under 5mm and the head diameter is 16.25mm

Might be worth checking that the engine has the correct adjuster screw on the operating lever; slotted head which is domed towards the thread for the lever to pivot on.

Hope this helps, good luck
Butch
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Joined: 15 Oct 2016 16:47
Location: Essex
Location: Mid Essex

Re: Clutching as Straws.

Post by Butch »

Thanks for taking the time to check that out. Gives me another line of attack.

I'll report back in due course.
harrymuffin
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Re: Clutching as Straws.

Post by harrymuffin »

If your clutch is dragging then the centre of the clutch is binding on the plastic 'thrust washer'. If you remove the clutch centre you will see a white nylon ring that locates into the four holes that hold the clutch basket to the gear wheel behind the casing. There should be shims on the shaft that the clutch centre locates on. If there insufficient then the clutch centre will bind on the nylon thrust ring. Shims should be added onto this shaft such that there is just sufficient clearance between the clutch centre and the nylon ring/thrust washer, if too many are added then the clutch will be a bit digital - grabby. Benjy Straw did a very nice and simple set of instructions with a diagram of what you have to do for adjusting the clutch and if you want a copy send me a PM and I will forward you a copy.
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72degrees
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Re: Clutching as Straws.

Post by 72degrees »

harrymuffin wrote:If your clutch is dragging then the centre of the clutch is binding on the plastic 'thrust washer'. If you remove the clutch centre you will see a white nylon ring that locates into the four holes that hold the clutch basket to the gear wheel behind the casing. There should be shims on the shaft that the clutch centre locates on. If there insufficient then the clutch centre will bind on the nylon thrust ring. Shims should be added onto this shaft such that there is just sufficient clearance between the clutch centre and the nylon ring/thrust washer, if too many are added then the clutch will be a bit digital - grabby. Benjy Straw did a very nice and simple set of instructions with a diagram of what you have to do for adjusting the clutch and if you want a copy send me a PM and I will forward you a copy.
I suggested checking the clutch 'shimming' early on in the saga. Opinions differed on whether it could induce dragging if there was zero end float ;)
The hill climber is still behaving in a rather binary way despite being perfectly 'shimmed' as far as I can tell but I suppose I should check it again. Perhaps the primary gears and or bush are worn allowing extra 'slop' which is making it worse? Oh well, you only use it once on a run - but a progressive clutch makes for a better launch and 64 ft trap time. I may try the just give it the beans and dump it strategy at Curborough this weekend. The new 'ace' bars should help to keep the front wheel down.
Butch
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Joined: 15 Oct 2016 16:47
Location: Essex
Location: Mid Essex

Re: Clutching at Straws.

Post by Butch »

Update;

Ordered some shims from NLM Friday morning, they were on the mat Saturday morning. They provided three shims of varying sizes - all quite thick ones. Pulled my clutch again in the afternoon and found I had three thin shims in there, all the same thickness. A bit of trial and error showed that it was pretty much shimmed up perfect as was. So it all went back together with the three shims that were in there.

Next up will be checking the actuator push rod lengths, and the amount of cable pull my clutch lever provides, though it take a fair squeeze as it is. Again, thanks to all here for their input to my continuing issue.

B
Butch
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Location: Mid Essex

Re: Clutching at Straws.

Post by Butch »

Test rode on the morning commute today. No better - no surprise.

Off roading the bike this coming weekend up the Peddars Way - Thetford to Hunstanton in Norfolk so we'll see how that goes I suppose.
Butch
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Location: Mid Essex

Re: Clutching at Straws.

Post by Butch »

Anyway, took the beast on its first serious off road foray at the weekend. As noted - running the Peddars Way from Thetford up to Hunstanton in Norfolk. I’d have to say that the bike was very capable out there too, though it was the first time I’ve ridden my own bike in such conditions, which kind of puts a different perspective on things. Still managed to face plant once – my excuse being the desert tyres not being up to wet grassy ruts. And bottomed the forks with a hell of a clang hitting one dip at speed.

Clutch remained f-ing awful throughout. Even the recently replaced cable was creaking roughly. So next up will be checking the push rod length, actuating arm angle, lever pull and another cable.
Butch
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Location: Mid Essex

Re: Clutching at Straws.

Post by Butch »

Bear with me if this sounds like an egg sucking exercise, I’m just trying to get my mind around this …

I now have a set of clutch push rods and yet another new cable for the Camel, all from NLM of course. Of the rods - I have two short lengths of the same diameter, which have clearly been heat treated at each of their ends. I’d guess they are silver steel. There is then a shorter rod of slightly increased diameter. They have also sent me a mushroom ended rod, which I don’t think I’ll need; I’m used to seeing that one as the splayed end of the mushroom sits against the pressure plate and I’ve been in there a lot of course. There is also a small steel ball, which must go between two of the rod ends when assembling it all up I suppose. If it actually needs all of the stuff – which is only to give a linear push between the lever on the left of the engine and the clutch on the right of course then I’d say that is a bit of a bugger’s muddle.

On the shimming for the clutch which I checked only recently, it is of course important to find the Goldilocks spot. Though with this particular bike that may be more or less critical. I’ve been thinking some more on this. If you have too much shim then the inner drum will rub more on the outer one. So in effect you would have clutch drag even before you assemble up all of the plates. So in theory you shim to just no slack. There is a nylon spacer in there which you should just hear rubbing as a witness. Mine is cock on with that instruction.

HOWEVER

If you have too little shimming you have movement between the inner drum and outer. The primary gears behind this are helical cut so if you have slack here then as you release the clutch the helical gears bang the drum out and you are left with pretty much an on off clutch with little slipping in between. So you get a stall or a tantalising take off. Thinking on this, that action must force one drum harder against the other, which going back to the over shimmed situation would give clutch drag. And it would only do it with the engine running which would explain why mine is fine turning the various bits by hand on the bench or pushing the bike around the yard with a dead motor.

If this is the case then I’m wondering if it points to a problem with the primary drive somehow. Maybe something there is badly shimmed leading to too much pressure on the clutch. So the plan is to try the new rods and cable, but I don’t expect that to help. Then I’m going to reduce the shim stack height to introduce too much slack into the drum assembly – by as little as I can with the shims that I have. That should at least make some difference.

Upshot may be that I will need to strip into the next casing behind the clutch to look at the primary. Maybe?

Does this sound at all feasible? or am I going down a dead end here? Cost and effort is mounting and I’m not making headway at all.

Thank you for listening.
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72degrees
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Re: Clutching at Straws.

Post by 72degrees »

Can't help with the specific arrangement of rods and ball on a 500 and I can't remember what was in the 350 I just rebuilt. Presumably the pressure plate is being pushed out as far as it can be - or will be with the new rods. A well known dodge for a draggy clutch on YZ250s of the mid 90's is to get more movement on the pressure plate and less drag by inserting a valve shim in an appropriate place in the actuation train.

As to binary clutch, then I suspect a very badly worn thrust washer and/or primary gear bush could exacerbate it even if seemingly shimmed hub/basket correctly. I'm beginning to think that might be the case with my 'race' engine but I've yet to swap over the plate stack and hub/basket yet but if that doesn't cure it I will delve in to the primary side more this winter.
'It must be a .....'
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Re: Clutching at Straws.

Post by 'It must be a .....' »

Hi again, with reference to my earlier post on clutch push rod lengths; I measured the rods in a 500 Camel and 500 5 speed and they were the same and there are NO ball bearings and both engines have no clutch problems.

I have since looked at 500 5 speed and 501 Camel parts books and there are NO ball bearings listed.

Of course NLM could have changed lengths to allow for a bearing?

Hope this helps? good luck.
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72degrees
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Re: Clutching at Straws.

Post by 72degrees »

Well, that's interesting. I came to swap the plate stacks to see if the binary clutch issue was transferred with them and found that the brand new last November plain plates in the racer on/off clutch were distinctly rusty and pitted! Dry as a bone in there (of oil at least as it should be given all new seals when rebuilt) but it looks as if damp must have got in standing over the winter. The 'conical' plate was almost stuck to the first friction plate. I suspect the one on the 375 may be nicely progressive as the plates have a remnant of oil contamination from the last time the seals went. I'm 'dressing' the plain plates on wet and dry on a sheet of glass and will try it again. If no better I'll go ahead with the swap - I don't think a misting with WD40 is the best (though tempting) strategy to adopt. The 'shimming' was, as I remembered, perfect.
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Ming
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Re: Clutching at Straws.

Post by Ming »

72degrees wrote:...- I don't think a misting with WD40 is the best (though tempting) strategy to adopt...
But the same clutch (basically) works in oil in the 250, so might be worth a try?
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72degrees
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Re: Clutching at Straws.

Post by 72degrees »

Ming wrote:
72degrees wrote:...- I don't think a misting with WD40 is the best (though tempting) strategy to adopt...
But the same clutch (basically) works in oil in the 250, so might be worth a try?
I assume the friction material is different. The plates certainly look different in the parts list. When I've had a really bad clutch oil seal failure on a 350 I have had 'slipping'. Anyway, I put the smoothed up plates back in and it's a lot better, but riding the 375 this afternoon reminded me again just how progressive the clutch is on that, so I may try the stack swap anyway out of curiosity.
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