Bad Clutch Slip..with New Plates!

[mspenz]

Check you have the correct amount of plates in the right order.

I don't think that the clutch would work at all (and it would probably be very noisy) if things were the wrong way around and I'm pretty sure that are right...I'll double check though.

[mspenz]

Hi Mike,

 

Try using Putoline Nano Trans GP - http://www.splatshop.co.uk/putoline-nano-trans-gp.html

 

When the clutches are worn, it makes a huge difference, you can freshly swap the oil with Putoline Light Gear Oil, and it will slip, change again with Nano Trans and it will work perfectly.

 

Also see the following info below that Chris has done to help people out:

 

The clutch fibre plates are 2.73mm when new

The steel plates are 1.53mm new

The clutch pressure plate is 5.30mm from where the friction plate makes contact to the outer edge.

The clutch hub is 3.00mm from where the friction plate makes contact to the machined outer edge, the hub can also get quite grooved where the steel plates sit causing problems with clutch slipping and sticking.

The basket is also prone to getting grooves where the friction plates sit, again causing problems with clutch slipping and sticking.

Clutch springs can loose their springiness, the free length of the spring from new should be 45mm, if they get below 44mm they will cause slippage in high gears under high load.

If the spring have shrunk replace the springs http://www.splatshop.co.uk/sherco-clutch-springs.html or we do some washers to put extra tension on the springshttp://www.splatshop.co.uk/shim-washer-14x20x1-din-988.html

We have found the main reason for the clutch to drag (other than mucky oil) to be the friction face's on the hub and the pressure plate been out of square, so if you have the equipment it might be worth clocking up the friction face and the clamping face to ensure they are parallel

to each other, if not you can give the friction faces a quick clean up on the lathe assuming there is enough material left. With these faces being made of aluminium they usually wear more than the friction plates.

Also I assume you have changed the oil recently, if not I'd recommend changing it. I personally change my gear oil every couple of months so it probably gets changed about every 8 times I ride the bike, this helps keep the clutch working well.

The oil type makes quite a noticeable difference to the response of the Clutch, Putoline Nano Trans GP is the best oil we've tried in the Sherco, especially with the clutch, it's pretty good with the gear shifting too and it seams to work for a long time before it needs changing.http://www.splatshop.co.uk/putoline-nano-trans-gp.html

Ipone's Box Xtrem is also pretty good and not quite as pricey

http://www.splatshop.co.uk/ipone-box-x-trem-1ltr.html

See the picture below for the washer that might be missing that causes very bad clutch slippage (highlighted in red) http://www.splatshop.co.uk/sherco-washer-a82035.html

This washer behind the clutch hub should also be 1mm thick

 

The clutch thrust bearing is 2mm thick

The washer for the above bearing is 1mm thick

 

Cheers,

Tim

Thanks Tim, what a brilliant detailed reply!

 

I'll do the simples first (measure plates, thrust etc) before delving in, you have me thinking about the clutch hub washer (M208) but I have the old washer here along with the rest of the elderly replaced parts and I've also found a couple of invoices from you guys with all the new parts listed as supplied and I don't have any 'extras' lying around.

 

The old basket was notched but the hub was still pretty good so I don't think that the plates are 'hanging'. Does the oil really make a significant difference?

 

The old plate set up didn't have any drag either, only slip under load in the higher trail gears...but not so much as there is now ??

 

I currently have a BM 1150 in bits with the gearbox out and a CCM SM with the back end off in the shed at the moment so space is severely limited but I'll try to make some progress this weekend. 

 

Cheers,

 

Mike.

[tony27]

1 other thought 

A couple of Shercos ago I ended up with major slip which was caused by the bellvue washer used behind the clutch hub nut not doing it's job allowing the nut to sit proud of the end of the layshaft which meant the clutch release bearing wasn't fully returning 

While you have the pressure plate off have a look at where the nut sits & retorque if needed

The reply from Tim at Splatshop is why so many of us hold them in such high regard, they've helped me out a couple of times even though I live as far away from the shop as humanly possible 

[mspenz]

Got It!

 

I'll post the result once I've heard back from John at offroadmotouk...

[mspenz]

1 other thought 

A couple of Shercos ago I ended up with major slip which was caused by the bellvue washer used behind the clutch hub nut not doing it's job allowing the nut to sit proud of the end of the layshaft which meant the clutch release bearing wasn't fully returning 

While you have the pressure plate off have a look at where the nut sits and retorque if needed

The reply from Tim at Splatshop is why so many of us hold them in such high regard, they've helped me out a couple of times even though I live as far away from the shop as humanly possible 

Good shout! It's proud by about 1mm so all seems to be in order there.

[mspenz]

The new plates are nearly all down on the specified thickness, that combined with some wear on the hub face and on the cover face was obviously too much to keep the pressure on under load!

 

I should have measured my old plates first but had already decided that I'd put a fresh set in since I was doing all the other bits under the clutch, my own steel plates all measure between 1.5 & 1.53mm and my friction are between 2.7 & 2.73mm....all good.

 

The new steel plates vary between 1.46 & 1.49mm and the friction plates vary between 2.62 & 2.68mm, quite a bit lower than they should be so likely a manufacturing process / quality control issue.

 

I put my old plates back in with the new springs (which measure 3 @ 46mm & 3 @ 44mm....my old springs are 43mm) and it's a transformation, I first tried it and slowly built up to around 35mph in 4th before cracking open the throttle expecting the slip again, wrong, the front wheel came up so quickly and I just managed to dab the brake or I'd have been off the back and lying in a field covered in cow **** 

It does the same in top.

 

I'll still add those shim washers mentioned by Tim until I decide if I can keep the bike longer, if so I'll replace the hub and cover and do it properly.

 

John has been totally understanding and has asked for the plates back so that he can examine them and replace as necessary.

 

Many thanks for all the advice and helpful information 

 

Now I just need to find somewhere I can get out more often...

 

Mike.

 

[mspenz]

I must add that John from offroadmotouk has been absolutely brilliant to deal with so I have to make that clear   .

 

The plates are slightly under the thickness of my originals but they are from Sherco and well within tolerance, there's maybe been a slight change in the manufacturing process over time which would explain the new plates being slightly different!

The main problem is probably the fact that the hub and cover faces are worn enough to let it slip with the slightly thinner plates which wouldn't be a problem in another bike without the same amount of wear, my one is obviously borderline but isn't slipping with my old plates and the new springs...at the moment anyway.

 

Mike.