C: Clutch G96

[timetraveller]

Kevin, I think that you might be overthinking this. Have you put a long piece of stiff wire or a length of 1/4" inch rod into the gearbox main shaft and measured how far in you can push it? If you do that and operate the clutch lever you might even be able to feel the lever arm trying to push against the stiff wire or rod. My guess is that there is something left in the hole but there is no magic or hidden subtlety involved. It is a straight hole that requires something straight going through it. From the figures you have given it seems that there is something about two inches long in the hole.. Have you ever had the kick starter cover off since you owned the bike? There are some clever people who have made a short length of rod with a forked end which will fit over the lever arm and prevent the rod rotating and wearing a groove into the lever arm. You might find that you are lucky enough to have one of those.



On another front when I started supplying the needle roller thrust race conversion for the twin clutches I did use 7 mm diameter silver steel. The idea was that this was a nice fit inside the main shaft tunnel and would further help to prevent any tilting of the outer clutch plate. However, once the Spares Company started to stock them they asked me to keep to the standard ¼” diameter as there is a bush inside the clutch end of the hole through the main shaft. I used to knock this out to allow the 7 mm rod to pass through but it seems most people did not want to do that and so they are all provided with ¼” diameter rod now.

 

[Vinnie Boy]

I think I have heard of owners using a mini car valve to encourage the pressure plate to lift squarely you would then be looking at lopping off a couple of inches from the push rod as has been done to one piece. Is something like that hiding coyly up the hole?

 

[Bill Thomas]

That's what I did many years ago on Twins.

 

[timetraveller]

That is what I did for the first one for myself. However, once I made some for other people I thought it was too crude and designed the present ones.

 

[Kevin Emery]

Hello Bill

I checked G93 and it is connected the right way around.

I thought there couldn't be anything left in the shaft but shone a light through it anyway. I couldn't see the light! I pushed a length of welding rod and out came a length of rod and another ball bearing. So my two piece rod was in fact a three piece rod with two ball bearings. Just as a check I measured it and it was exactly 1 13/16" in length !!!

I will go off now and eat my humble pie.

You win first prize Bill. Thank you everyone else who have contributed to the solution.

 

[Bill Thomas]

We are all still learning Kevin,
Tricky Bikes these, I thought T.T. got it first, But no matter as along as you got there.
So much to remember, Trust nothing !.
Well Done, Bill.

 

[Kevin Emery]

Just to complete the thread. Please see below a photo of the three section push rod removed from bike. The total length is 12 7/16" which is slightly too long. This is good as I suspected the pushrod was too long.
Thank you all for your help with this.

 

[Mikeant]

I think that I have the same problem, a slightly overlong push rod being a combination of two rods and a ball. Initially I had the situation that the clutch end adjuster C42/1 was drilling a hole in the outer cover. So I tried to move the pushrod the other way and then found that the gearbox cover screw ET27 was hitting the kick start crank. Could well be that when I first built the engine in 1976 I converted to two rods and a ball bearing and did not shorten one rod to allow for the ball. OK this is easily sorted. However I have another vexing problem.

The friction part of the clutch is slipping. C21 rearplate is new, A front plate C23 is on order with the Spares Co. meanwhile my original plate is installed and it is flat. The drum C1 was modified in 1976 to take a one piece friction disc C24/1. This is not worn as the bike has hardly been run since this initial build. New springs of the correct length have just been installed and they are not binding in the cups. With slack in the cable so the clutch is fully under control of the springs, the clutch slips. I cannot see how installing a new front plate when it becomes available is going to change things. All was thoroughly wiped with Acetone. Any suggestions?

This is particularly frustrating as the rebuild is all but finished, the engine was started with a tow and sounded great but the clutch was clearly not 100%. Stu has overhauled the servo part and C13 centre part rotates correctly with 5 thou end float and pushes out the shoes onto the drum.

 

[Robert Watson]

Look on the back side of the inner primary clutch plate C21 and see if there are any witness marks where it has been rubbing on the ends of shoe pivot bolts C5/1 If there is contact here the primary clutch cannot fully engage and slips. A little grinding on the ends of the bolts, but not too close to the snap ring grooves, a little grinding where the witness marks are and assembling so that these two place are aligned (there are 3 different positions that the two bolts can be assembled to) and if necessary some very thin washers between C21 and the C13 clutch plate carrier ---- or all three in moderation!

Good luck

 

[greg brillus]

With the inspection cap removed from the kick start cover, can you move the top of the G91 lever left to right........Thus you can feel some free play in the lever.......if not then the adjustment, is too tight.......The extra length of the push rods will probably be the issue here. If there is no free play then the clutch will slip for sure.......... A standard Vincent clutch using the original 7/8" pivot handle bar lever should have quite a lot of free play in the cable assembly, as you are only lifting one pate to release it.