Bultaco M80 Clutch

[majesty320]

I have adjusted the clutch on my m80 as per the manual, but when I start it sometimes the kickstart engages and other times it will slip on the clutch. can anybody tell me if this is common, and how to cure this problem. Thanks Mark

[wilsonwash8]

I had the same problem with my Model 49. I bought new plates from Barnnett, replaced the inner clutch hub from a later model, and she worked fine. The original inner hub had the retaining pins that were a real bear, so I switched to one that had the threads. Might even be something as simple as your oil. What type are you using?

[john collins]

Change not to have ACU questions!

Very often on all Bultaco's - people buy clutch plates etc - when it is usually clutch adj that is incorrect.

Not sure which manual you are using ( bin is best place for most of them)

One problem I have found over 30 years of adjusting them is that it is best to go the whole hog - adjust and maintain whole clutch mechanism in one go - then thing work really well and is also lighter.

My method. May take a liitle longer - but is best.

1. I assume you have already looked at plates. On yours they will be all steel - not as easy to see wear as people pretend - and frankly although I have sold a lot - not as many as any other make - they are not a serious wear item as long as not abused etc.

If totally shot - the all steel plates will show real signs of wear when you look at them - but next steps will confirm it anyway. If you do find they are very worn - obviously you can but new ones - or if cash is tight - you can go over each one with a centre pop - but do it in a surface plate - and do not go mad.

2. You need to disconect all the cable and mechanism. By far easiest method is to remove the timing side cover. Remove the clutch plates from other side by undoing the nuts - or if you have the post and pin hub centre - compress springs and remove pins. There is a special tool - but you can easily make one.

After removing plates, remove what I call clutch mushroom ( about 40mm with flat head )

Remove clutch rod - by pushing out from either side with small screwdriver etc. CARE YOU DO NOT lose clutch ball.

Now is a good time to clean out the centre hole in the gearshaft that the clutch rod runs in - they tend to rust/crud up and a good clean with WD 40 - while working the clutch rod back and fo - or better still a similar dia piece of rod. Carefull if you are tempted to put a piece of rag in there you do not get it stuck.

3. Replace Clutch mushroom into hub on clutch side.

4. Re- place plates.

5. Check clutch thrust bearing is in place on outer clutch/spring retainer plate. Before you do this slacken of adj nut ( it takes 21mm socket) so that you can easily turn adj screw in centre of plate.

Use a little grease to hold thrust bearing in place when you put on outer plate.

6. Replace clutch cups and springs. Good idea to check no-one has put an odd ( short)

spring in here.

If you have post and pin - you have no control on spring tension - just compress spring - with dished washer on top and replace pins - care - or they fly accross workshop - this is why special tool is handy.

If you have threaded clutch hub - several methods really.

I - bottom springs - using a tubalar spanner - but when I say bottom - do not go mad or you will shear the threaded part. Just turn nut until it feels as if it does not need to go further - then slacken each one 4 complete turns. easier to count if you have a rod through your tube spanner - but easy enough whatever you do. This will usually leave about two complete thread showing at the top ( I mean you can see two threads on top of each clutch nut. If you do not fancy the bottoming method - you can just go to two complete threads showing in first place - but I prefer to bottom them.

You have not replaced any clutch rod/ball etc yet

7. Now you can find out if it was an adj problem or plate wear - as without rod and ball etc - and with the adjuster screw turned out half a turn from full in ( so it does not actually touch thrust bearing)

You can replace k/start lever and test. With your hand you can leave the timing case off.

If you are going to really test it - and need to kick it - best to but timing case back on as you are not so likely to bend k/start shaft. You can leave it off - but kick carefully - do not jump all over it!

You still have no clutch / clutch ball fitted.

No slip - your plates are OK and it is adj. Slip - plates are shot.

If plates are ok - or if you have needed to fit new ones - you can now carry on adjustment.

Take timing cover back off. Carefully refit clutch ball. Refit Clutch rod. On end of rod where it enters sleeve ( sprox) gear there should be a felt washer - to stop crud going in. A small disc of piece of rubber inner tube with slit works just as well.

Good time now to remove the clutch operating arm - and really clean and grease it so it is a smooth fit in the timing cover. It is retained by a shoukdered bolt. Check that the flat on the opertaing arm has an undamaged - half ball bearing shape on it ( it often gets damaged) Clean off any burrs on arm etc - and also check that the bore of the timing case where it fits is clean/smooth. Graese and turn by hand to ensure nice smooth action.

Replace timing case. New gasket is always best.

DO NOT FIT cable.

8. Adj as follows. Your clutch arm should be more or less positioned to it is at about right angles across he engine ie about 90 degrees to line of frame - actually just back from there is best - about one notch futher back towards rear. ( no more)

On other side turn the adjusting screw in - until all the play you can feel by hand on the operating arm is taken up - and then back off a little so you have about 2mm free play. In other words you can just wobble the clutch arm a few mm forward by hand until it becomes solid. Take up excessive play by turning adj screw - but never make it solid - so there is no free play - you need a few mm slack.

Inevitabvly when you try to tighten lock nut it will go out of adj - best to use 21 tubular with srewdriver through it to hold adj screw stready- or just use 21mm socket with T bar and when ready give the t bar a wack towards front of bike! You may need a few goes to get this right. Experiment!

Object is that you can move operating arm - by hand just few mm back and fo without feeling solid.

Absolute - no cable fitted. Final position will be clutch arm pointting back a little from halfway position. If you need to move arm take off spline and re-position- but do not have it more than a little further back than just past halfway.

Re-fit cable - and adjust at h/bar lever until you have 2-3mm free play at h/bar end.

If you find you have too much play at h/bar - either the cable is wrong/stretched - or the clutch rod is worn short or the clutch ball is the wrong one. Do not compensate for this by moving clutch opertaing arm - fix the problem.

If you really wish to set it up ( but not as critical as people think) pull cluch lever in and press k/start - clutch will slip - and you will see plates turn. Observe outer spring retainer plate - it will wobble.

If you have the threaded type clutch posts - you can play at adjusting nuts a LITTLE - in or out until pressure plate runs true - then thread some lockwire through nuts etc

If you have post pin - there is sod all you can do.

This will work