Anyone rebuilt clutch basket cush-drives?

[James P]

Yamaha workshop manuals say to replace the clutch basket cush-drive assembly if there is any play. I found about 2mm of play in this DT200R assembly (identical to SDR/DT125R/TZR125 except for number of gear teeth and likely very similar to all wet-clutch TZR250s), so thought I'd have nothing to lose by dismantling it to see what was inside.



The only assemblies I'd dismantled in the past (much older European bikes) had springs for the cush-drive, but this uses rubber buttons. The six large rubber buttons perform the main cushioning duty, while the three smaller ones fit into the holes on the spokes of the gear (to prevent rattling of the clamping plate, I presume).
One of the large rubber buttons is round, one is almost round and the remaining four each have a flat edge which matches the raised blocks on the aluminium basket portion when the parts are assembled. The round and almost-round buttons were found in different slots. I wondered whether all of the rubber buttons started off round, but those with a flat edge don't appear deformed - it seems to me they were made in that shape.
The red "gasket" thingy is 0.6mm thick, made from some tough material which reminds me of Elephantide - it seems tougher than usual gasket paper. It appears to have been chafed/torn/deformed by continual movement, probably caused by the play in the assembly.

Although absence of play in the clutch basket cush-drive would be desirable, I can't see how a small amount of play would be detrimental (now that I know how the internals are arranged). New assemblies are very expensive and are no longer available for many 1980s Yamahas. If one can obtain the rubber buttons, rivets and a gasket (Dan...?), the assembly should be easy and cheap-ish to recondition.

Anyone had any experience in rebuilding these and/or know the specifications for the parts needed, or where to get them?

Thanks & regards,
James

[silverstrom]

It's very common for the dampers to wear or break down and cause free play between the primary driven gear and basket. The allowable limit is zero.

Search Yambits for clutch rivet and clutch damper and you'll find both. It's an easy repair, but an extra set of hands helps when peening the rivets. I heat the rivet ends and then peen. When done grind the rivets back so you have the same protrusion as stock. The dampers are quite rigid so can be fussy to install. A drop of oil helps.

I've repaired several RZ350 baskets, but the principle is the same for yours as well.

[James P]

Excellent - thanks for the advice!

The rubber dampers in this particular cush-drive (the one in the photos) don't look worn and are not damaged, but do allow about 2mm of play. I can accept that excessively worn or split/damaged dampers should be replaced, but I'd be happy enough to re-use these ones if replacements are not available.

I'll have a look at the Yambits web-site.

Thanks again & regards,
James

[silverstrom]

As I said, the allowable play is zero. If you have movement you need to replace the dampers even if no damage is obvious. Over time the dampers harden and will shrink as they do so. If you don't replace them the 2 mm of play you have now will quickly get worse. The free play limit of zero is there so you don't hammer the basket as you dump the clutch and then have to take up that free play before making solid contact. That contact will result in damage if you don't fix it. 

[James P]

Yes - I'll certainly replace the dampers if I can get new ones. Although I accept that mine have likely shrunk, they are still quite pliable and I have a hard time imagining that they would crack or disintegrate until they had been used for quite some time more. However, I'll defer to those who have had more experience with these things than I .

I've had a look at the Yambits dampers and they are all round ones - none of the flat-edged type as in my photos. Yambits list dampers only for RD, RZ and earlier models. Although these are all the same (Yambits No.CPA026), I so far have no idea whether these are correct for SDR/DTR/TZR etc. - I will ask the dimensions.

Regarding the basket cush-drive assembly in my photos; I will unlikely rebuild it, as the clutch basket slots are quite badly notched (although could still be filed or milled flat). I bought the DT200R bottom end to get some spares for my SDR. The DT clutch gear has a different number of teeth to the SDR gear, so it would be of little use unless I change both primary drive gears.

Do the RZ350 cush drives have the thin "paper gasket" like that shown in my photos? Were these damaged? Did you replace them? If so, are they obtainable, or did you make your own?

Regards,
James

[jools]

James

I did a few on my old TZ's and a few LC's.

I used countersunk screws and threaded the back plates also fitting half nuts loctite in place with the threads peened with a centre punch.
This has worked well and is a common mod on the TZ350/250 baskets.

[epa police]

Fondseca sell rebuilt kits for the TZ clutch and the parts individually. Not sure they will fit your basket but the rivets might and its worth asking the question. I bought two sets off them last year but still haven't got around to doing the job but the parts look the job.
       http://www.fondseca.com/index.php?main_page=advanced_search_result&search_in_description=1&zenid=5bd70f351acde28e50531e444952a97d&keyword=clutch+rivets&x=27&y=6

[James P]

I've received a reply from Yambits. The round dampers on offer (CPA026) are 22mm OD and 8mm thick, while the rivets (YBK014) are 6mm diameter and 25mm long.
It appears that a set of dampers with 22mm OD will take up all free play in the assembly, although the ones I removed are about 10.5mm thick (could the thickness have increased as the diameter reduced? ).
The rivets I removed are actually 6.25mm diameter (they had to be pressed out after disassembling the cush-drive), but a length of 25mm seems about right.
In spite of the Yambits dampers possibly being about 2mm too thin, I think they'd be worth a try (in the absence of ones which are of "correct" thickness) - I could perhaps make up some spacers to remove any axial play.

...I used countersunk screws and threaded the back plates also fitting half nuts loctite in place with the threads peened with a centre punch.
This has worked well and is a common mod on the TZ350/250 baskets.

I was thinking along similar lines Jools - I'm glad to know that you have tried it successfully. In my case, the back plate is 3mm thick, but the holes are too large to be threaded M6. Of course, an option is to enlarge the holes and to machine shoulders on plain M6 nuts so that they drop into the back plate, giving as much thread as possible. The peened-over sections of the original rivets protruded about 2.5mm "above" the surface of the back plate, so I should be able to use M6 nuts about 5-6mm tall (with shoulder machined 3mm deep). I may even have the nuts welded in position. I'd probably fix the screws with Araldite or high-strength Loctite, so that all parts could be dismantled with minimum fuss later (if required). M6x25 coutersunk screws will be suitable, with any excess ground off as required.

Fondseca sell rebuilt kits for the TZ clutch and the parts individually.

Thanks for that Pat. Unfortunately the TZ cush-drive buffers seem to be rather too long to fit in the space occupied by the round or shaped ones in the DTR/SDR cush-drive assembly. The rivets may well work, but are five times the price of the Yambits ones (although it is a set of six, not four!). Apart from being countersunk, I don't think there is anything special about the DTR rivets - they are quite soft and were easily drilled. Besides, now that Jools has confirmed that the screw method works, I'd be inclined to go that way if I can make it structurally sound.

If anyone knows of any other likely sources of clutch basket cush-drive buffers (for any bikes) which may be good for my application, please let me know! If no better prospect arises, I'll buy a set of the Yambits buffers and see how they fit.

I'd also be glad to know if any other bikes use a "gasket" like the red one in my photos.

Thanks again to all who have replied so far!

Regards,
James

[Toop]

If anyone is interested I can have this in France ( or other type of head, material ... )

[Toop]

or this

[jools]

...I used countersunk screws and threaded the back plates also fitting half nuts loctite in place with the threads peened with a centre punch.
This has worked well and is a common mod on the TZ350/250 baskets.

I was thinking along similar lines Jools - I'm glad to know that you have tried it successfully. In my case, the back plate is 3mm thick, but the holes are too large to be threaded M6. Of course, an option is to enlarge the holes and to machine shoulders on plain M6 nuts so that they drop into the back plate, giving as much thread as possible. The peened-over sections of the original rivets protruded about 2.5mm "above" the surface of the back plate, so I should be able to use M6 nuts about 5-6mm tall (with shoulder machined 3mm deep). I may even have the nuts welded in position. I'd probably fix the screws with Araldite or high-strength Loctite, so that all parts could be dismantled with minimum fuss later (if required). M6x25 coutersunk screws will be suitable, with any excess ground off as required.


Regards,
James

James

you could open everything out so they would accept M8 csk screws - probably a better bet for added strength. just a bit of extra work to open out the countersunk holes to suit..

What I have done in the past is screw everything together, mount the finished basket in the lathe and turn the nuts down to the required clearance then peen the thread/nut joint with a centre punch

[4l04ever]

I think I used Wiseco Clutch rubbers when I rebuilt my LC clutch.  They may do different size ones.  Yambits don't have a good reputation for quality....

[James P]

you could open everything out so they would accept M8 csk screws - probably a better bet for added strength. just a bit of extra work to open out the countersunk holes to suit..

What I have done in the past is screw everything together, mount the finished basket in the lathe and turn the nuts down to the required clearance then peen the thread/nut joint with a centre punch

Hmm...not a bad idea Jools - definitely an option.

I think I used Wiseco Clutch rubbers when I rebuilt my LC clutch.  They may do different size ones.  Yambits don't have a good reputation for quality....

Thanks - I'll have a look.


Regards,
James

[Dmac]

I think I used Wiseco Clutch rubbers when I rebuilt my LC clutch.  They may do different size ones.  Yambits don't have a good reputation for quality....

+1 on that, They sent me some awful crap.

Footpegs, reflectors, cables - all junk

[James P]

My search for new replacement cushions/rubbers has so far been fruitless. I did see these (http://www.uppracing.com/item.php?pid=266&cid=71), which state "Banshee. Blaster...".
The Banshee and Blaster cushions are different (Blaster is the type I want), but the advertiser hasn't replied to my enquiry for more info after ten days .

It looks like I'll have to start talking to a urethane moulder...

When I get around to it, I'll dismantle one of my spare TZR 1KT clutch baskets to see what type of cush-drive it has.

Regards,
James