Snatchy clutch or Kangaroo petrol?

[nkt267]

I was clutching at straws(forgive the pun).I have 25thou rock at the edge of the clutch drum..I have this idea in my mind,could be wrong, that snatching is cause by an uncontrolled movement somewhere.
I suppose I'm really looking for the point where the primary stops working and the servo clutch takes over,I feel that the servo is cutting in too early.I think plunger pressure must be one of the main factors in this,please correct me if I am wrong.
I found that no matter what I do with the plunger spring the plunger will not lock and I really could not get the pressure that I felt should be there.The reason that I think that the plunger should lock if the thimble is screwed in tight is that a friend did this and his clutch slipped really badly,the plunger stopped the carrier from rotating so the shoes held off the drum.When we backed off the thimbles the clutch was fine.If I can get my clutch to work like his then I'll be happy as Larry..John

 

[Bill Thomas]

Not sure, But I don't think the plungers should lock, One of our top sidecar racers told me, He screwed them right in so as to get fast gear changes, The stronger the springs the quicker the shoes will come away from the drum, But some say if you do it too much , It will make the clutch slip ! The outer plate clutch must be able to move the shoes into place to lock on the drum, If you try to turn the shoes , By hand on the pins, With out the outer clutch not fitted , You can see what is working, One way is for Kick starting and over run, The other way is Drive. If the plungers are not touching the pins, The slack will allow the shoes to flap about and maybe touch the drum befor you want them to, There should be 25 thou between the shoes and drum at rest.Cheers bill.

 

[BigEd]

I suppose I'm really looking for the point where the primary stops working and the servo clutch takes over,I feel that the servo is cutting in too early.I think plunger pressure must be one of the main factors in this,please correct me if I am wrong.
I found that no matter what I do with the plunger spring the plunger will not lock and I really could not get the pressure that I felt should be there.The reason that I think that the plunger should lock if the thimble is screwed in tight is that a friend did this and his clutch slipped really badly,the plunger stopped the carrier from rotating so the shoes held off the drum.When we backed off the thimbles the clutch was fine.If I can get my clutch to work like his then I'll be happy as Larry..John

The plate clutch is the servo as this is a light clutch that engages the main clutch by pushing the shoes onto the drum.
If I correctly understand what you are saying you are on the right track. In relation to the C7 shoe plunger, if your friend had the thimble screwed right in then the pressure was too great for the primary clutch to overcome so the shoe was not forced hard into the drum. As you said, when he backed off the thimble and thus the pressure, the primary was then able to apply sufficient pressure to the shoe. In an instance as described the C7 pressure can be backed off a little at a time until the main clutch grips. If you slack it off too far it will start to grab. It is not an easy thing to get your head around until you study all the bits.
Read "5" again in my previous post.

 

[Rob H]

Had the same problem with the clutch on my twin which sometimes was so fierce it felt like it would snap the chain. I contemplated replacing with a multiplate but decided to recondition the original at a similar cost. When I took it to pieces, found that the edge on one of the shoes had broken away a little. Got new shoes, friction plate, inner and outer steel plates and a bearing lifter to ensure the plate lifts squarely, plus replaced all bushes as a matter of course. Result being was transformed, super light and super smooth, no slip.

The only problem I had was with the setting up of the pusher. Using the bearing type means that you have to remove the screw adjustment from the outer plate and have to cut the pushrod to the exact length. This very time consuming and pretty impossible to get it right first time. In order to set the adjustment I got some shims made up which will also allow for future adjustment when the friction plate wears. Not sure how this can be done otherwise.

As an aside I remember reading an article somewhere that either Conways or Kemp offer a service to set up the shoe sprigs on a special jig they have

 

[greg brillus]

John if you are trying to see if you can feel the point where the pilot clutch engages the shoes on the drum you may be waiting a long time.....!! How have you set up the cable....? If your clutch lever at the handlebars is standard, that is that the pivot points are 7/8 of an inch apart, you should have quite a lot of freeplay at the lever, say a quarter of an inch. If you have very little, you will find the clutch engaging too late when your fingers are outstretched the most, and the take up point on the clutch will be savage because you have lost control at the right point. Remember that you are only lifting one plate, and when all is set up right, it takes very little movement to actuate the clutch. The plungers should take a good strong push with your thumb to compress, and one will be weaker than the other. It is also important to Loctite the grubscrews in place with some medium strength blue 243 Loctite when done, or else they can come undone by themselves. This I do by putting some on the threads once I am happy with the adjustment, then back the screw out two turns, so it picks up on the Loctite, then wind in the two previous turns, so it is back where it was, then wipe out the excess with a rag and small screw driver down each hole. Do not use red high strength Loctite or else you will never move them in future. Look carefully at the picture Bill posted earlier, and it shows how much travel each plunger should have, you can set this up first without the springs, by moving the plunger in and out whilst adjusting the grubscrew, then count the number of turns to remove the screw and refit the springs, and so on. The amount of travel actually dictates how much tension is on the springs, the springs should not become coilbound to limit travel, and over compressing the springs actually damages them......Keep at it, and you will have a great clutch, all the best.......Greg.

 

[John Cone]

Also forgot fitted new C14 pins,all of which reduced the plunger to pin clearance..John

Hi John, My main clutch has turned out to be the cause of all my gear engagement problems. I have taken it to the miester, Bob Culver, who shew me what was wrong. All the springs were broken, the holes through C3/2 were badly elongated and someone in the past had drilled out the shoes and put in bushes where they connect to the carrier, but they were out of centre. Hopefully get it back this week, with new shoes , and main carrier C3/2 , springs and plungers.

 

[b'knighted]

As an aside I remember reading an article somewhere that either Conways or Kemp offer a service to set up the shoe sprigs on a special jig they have

Bob Culver has a jig, possibly the original and relined my shoes and reset my plunger springs, several years ago, for a very reasonable fee.
I posted my shoes to him and he noticed that there was a crack in the thin wall of the plunger housing I think on C7/1. This shoe had to be replaced with a second hand one which Bob relined and reset to match.

 

[timetraveller]

Regarding Rob H's posting above (34), he should have received an instruction sheet with the needle roller thrust race modification for the clutch lifting mechanism. It is certainly true that one looses one adjustment, the one in the middle of the original clutch outer plate, but that still leaves two; the one in the kick starter cover and the one in the clutch cable. I do not have the instructions with me for reference at the moment but it should read along the following lines. First put the adjustment in the kick starter cover in the middle of its range. Roughly assemble the clutch with the new parts and measure how far out the outer clutch plate is from the friction disc when it is pushed fully inwards. Then shorten the newly supplied push rod by that amount. Note that one end of the new push rod is left soft and the other end hardened (discoloured) so there should be no doubt as to which end is which. If you are doubtful about getting it right first time then make sure that you cut too small an amount off and then repeat the measurement.. Once you have it right, fit the push rod into the top hat shaped part and fix it with either silicon mastic or Loctite. You are then left with the possibility of combining adjustment of the cable length and the kick start cover adjustment to ensure that there is enough clearance and enough cable slack to give everything a nice feel. There should be absolutely no need for shims or any other finicky means of adjustment. I'm a simple lad and try to make any mods simple for others too.

 

[nkt267]

In an instance as described the C7 pressure can be backed off a little at a time until the main clutch grips. If you slack it off too far it will start to grab

Yes I made a good note of this,I had sort of figured out that the plunger pressure controls how quickly the shoes engage, but hadn't appreciated how important the amount of travel could be.
Anyway last night I made a new plunger a little longer than the new one I bought so as to get the plunger in a better position with the C14 pin.I also did not drill as deeply for the spring recess so that the sring pressure would be a little increased.
All was assembled last night and left till this morning. In the meantime I read Greg's post about checking the travel of the plunger,so I got out a C7 shoe that I was given to play with. I checked the plunger travel as Greg suggested and found that I only had to back the thimble off 1/3rd of a turn from fully in,a lot less than I thought and have read about in other VOC sources ie Whitikerpedia.
Interestingly when I put my clutch back together last night I only had the thimble backed off about 3/4 turn from the bottom,I need to recheck this inlight of todays information.
BUT I ran the bike up the road today,more slack in the cable as per Greg's post and I seem to have a clutch..When I can give it a good run I will report back..John

 

[Rob H]

Regarding Rob H's posting above (34), he should have received an instruction sheet with the needle roller thrust race modification for the clutch lifting mechanism. It is certainly true that one looses one adjustment, the one in the middle of the original clutch outer plate, but that still leaves two; the one in the kick starter cover and the one in the clutch cable. I do not have the instructions with me for reference at the moment but it should read along the following lines. First put the adjustment in the kick starter cover in the middle of its range. Roughly assemble the clutch with the new parts and measure how far out the outer clutch plate is from the friction disc when it is pushed fully inwards. Then shorten the newly supplied push rod by that amount. Note that one end of the new push rod is left soft and the other end hardened (discoloured) so there should be no doubt as to which end is which. If you are doubtful about getting it right first time then make sure that you cut too small an amount off and then repeat the measurement.. Once you have it right, fit the push rod into the top hat shaped part and fix it with either silicon mastic or Loctite. You are then left with the possibility of combining adjustment of the cable length and the kick start cover adjustment to ensure that there is enough clearance and enough cable slack to give everything a nice feel. There should be absolutely no need for shims or any other finicky means of adjustment. I'm a simple lad and try to make any mods simple for others too.

Yes did receive an instruction with it maybe did not read it carefully enough. Think the issue was that I did not realise that you could set the lever in the kickstart cover at the middle of its range, I thought it had to be at almost the outermost of its range to get the maximum lift., thanks for the tip guess will have plenty of adjustment left now!

Actually have another problem maybe you can advise, clutch works fine now, at low / normal speeds but does not like to disengage at high rpm when trying to accelerate hard. Would this be due to weak springs in the shoes?
regs