Replacing clutch plates, a pictorial

[Suzuki_Don]

My experience is that I had the same problem with my 550/700 (75hp). I pulled out to pass a 4WD vehicle and when I was beside him with oncoming traffic all of a sudden there was no drive to the rear wheel. Heart immediately moved from chest cavity to throat. Luckily I throttled off and on again and I got the drive back and passed the 4WD in plenty of time. Did I mention I was going uphill at the time.

I then fitted EBC friction plates and found that the gear changes, particularly in the lower gears and moving at low speed in traffic where many gear changes are required, were very notchy and sometimes could not get the bike out of gear. I had also fitted three of the six EBC 10% extra rate springs to the pressure plate. This made the clutch extremely heavy in use. Glad I didn't put all six EBC springs in.

So I then pulled the clutch again as I couldn't ride with the bike in this condition. I measured the tabs that fit in the outer section of the clutch basket and found that they were all over 12+mm. When I measured the originals they were on average 11.8mm and I remember when fitting the fibre plates they were quite a tight fit in the basket, I had to line them up very carefully to get them to slide into the basket.

So armed with this new information I filed the new plate tabs down to 11.8mm each on the side of the tab that does not take up the drive on account that if my filing was not absolutely square the plate and tab might be bearing on a small part of the tan if you know what I mean.

So I reassembled everything with the curved side of the steel plates inwards and installed this time the six new OEM clutch springs.

And from then on it operates perfectly. No slippage at full power. Light lever pressure with OEM new springs. And good and easy gear changes.

So this is the way to go in my opinion. New fibres with correct size drive tabs and new OEM springs. Works really good unless you have a really hotted motor like CHEF.

[Graham]

Something that was missed in the pictorial was checking if the steel plates are warped. Lay the plates on a flat surface (like window glass) and use a feeler gauge to check distortion. 0.1mm or less is normal. Check model specs.
Warped clutch plate makes a clutch unadjustable. A clutch that drags (hard to find neutral) when pulled and slips when released (under heavy load) may have a warped plate.

[Suzuki_Don]

Lay the plates on a flat surface (like window glass)

1/4" thick plate glass is best.

[Graham]

Might wish to mention you want to use the same oil used in your bike (no friction modifiers, such as diesel motor oil).

If you use "regular car" oil to soak them, you can have problems.

Nice writeup, and thanks for sharing!

- JC

Why and how did you come to the conclusion that the type of oil that clutch plates are soaked in is going to matter, car or motorcycle?

[Graham]

Most "car" oil has friction modifiers which will interfere with the proper operation of the clutches. That's why we use "diesel" oil in our bikes.

Soaking the clutches in the wrong oil will contaminate them and can cause them to slip.

- JC

I did read some stuff about friction modifiers but the words are “could interfere” not “will interfere”. To think about it the clutches didn’t slip because of friction modifiers 30 and 40 years ago when they became poplar. Has anyone ever tested this? Could it be somebody wants to sell high priced motorcycle oil? But then again I never heard of any issues from using oil for diesels in motorcycles either. But this is not the thread for this discussion.

[Milktown]

HELP!! first off this is my first post (tho I've been lurking for a while) so hello to all. I'm am the proud owner of a 79 gs425 and a 78 gs750. Today I was replacing the clutch plates on the 750. Was almost done, tightening the clutch spring bolts when the last one broke off halfway inside the threaded cylinder thingy. I tried drilling asmall hole in the bit of the screw that was left in there but it broke off at a funny angle so I couldn't get the bit to bite. So the next thing my genius mind decided to do was drill the whole thing out and cut new threads. Same problem as before the bolt broke off at such an angle that I can't get a centered hole going. I got to a point where I just stopped before I cause any more damage as you can tell I am a novice mechanic at best. Any suggestions on where to go from here?

[Nessism]

HELP!! first off this is my first post (tho I've been lurking for a while) so hello to all. I'm am the proud owner of a 79 gs425 and a 78 gs750. Today I was replacing the clutch plates on the 750. Was almost done, tightening the clutch spring bolts when the last one broke off halfway inside the threaded cylinder thingy. I tried drilling asmall hole in the bit of the screw that was left in there but it broke off at a funny angle so I couldn't get the bit to bite. So the next thing my genius mind decided to do was drill the whole thing out and cut new threads. Same problem as before the bolt broke off at such an angle that I can't get a centered hole going. I got to a point where I just stopped before I cause any more damage as you can tell I am a novice mechanic at best. Any suggestions on where to go from here?

I recommend a new center clutch hub. Shouldn't be hard to find from either here in the parts wanted forum or ebay.

http://cgi.ebay.com/ebaymotors/1978-suzuki-gs750-gs-750-dohc-sm104-clutch-/230611315727?pt=Motorcycles_Parts_Accessories&hash=item35b1816c0f