This is a problem I have had for quite some time & have had no luck solving it.
I have the 4 spring clutch type fitted.
In my attempt’s to fix the issue I have replace the following with all new parts.
Clutch cable, conical spring in the right hand casing, pressure plate springs, friction plates.
What is happening. All the year’s I have had this bike when I have released the clutch lever the clutch would engage immediately, now the clutch will only engage when the lever is just about fully released.
This is making riding the bike quite difficult.
I have spent literally hundreds of hours making countless adjustments to fix this issue.
I can see what the problem is, there is just too much outward travel of the clutch pressure plate when the lever is pulled in & when released that travel means the clutch engages when the lever is just about fully released.
Andy, I’m assuming the bike is a pre unit Triumph twin with a BSA type 4 spring clutch.
Sounds like you’ve had it all to pieces so you understand how it operates, all the bits are there (using the parts book to check) they fit correctly and have checked their condition.
Correct adjustment is everything on these - if the clutch makes a clicking noise each time the lever is pulled then the three ball bearings in the lever assembly are being pulled out of their cups, adjusting will stop this.
Adjustment should be to slacken everything off. Both ends of the clutch cable and the push rod aduster nut and pin.
Once all is loose then turn the push rod adjuster pin until you can feel it touch the push rod just as it’s about to lift the pressure plate. Turn the aduster pin back a quarter to half a turn and lock it off with the lock nut.
Then, through the gearbox outer cover access hole, tighten up the cable until the nipple is touching the lever on the assembly.
Then adjust the cable at the handlebar clutch lever so it has about an eighth of an inch slack at the lever.
If the travel is still too much then I would suspect the push rod operating length. Have you installed a new push rod? Or done something that would cause the operating length to change.
I suppose a new stronger conical spring could cause the length to change slightly but nothing that corrct adjustment wouldn’t take up.
Try shortening a spare pushrod and see if that helps (remember to harden the ends or they’ll mushroom).
Let us know how you get on.
Edit - Andy, sorry just seen you have a 3TA on your other post some parts of the above may therefore not apply as I don’t know my way around those clutches in any detail but I assume trhey should be basically alike.
Just looked at the parts catalogue - yep, much the same as their later bigger brothers but with a few extra pieces:
The whole clutch operation is super smooth, no clicking, binding, nothing is worn, the pushrod is the correct length.
There is only the adjuster in the gearbox outer cover that is on the spoke (where the cable nipple goes in) that lifts the 3 ball ramp, along with adjusting that up & down and the adjuster on the lever it makes no difference, the travel stays the same.
If I was to put a shorter push rod in the adjuster screw in the pressure plate would not reach the rod ?
I did think about making another push rod out of some silver steel.
Andy
There is an adjuster on the clutch side (under the access plug by the left footrest) with the locknut and adjuster screw. That effectively varies the length of the push rod.
Only adjust that once the cable is slackened off. Then re-do the cable.
Numbers 17 and 18 on the parts diagram above.
The pushrods are pretty cheap (about a fiver) and are easily replaced through the clutch adjustment access plug if trying for a shorter one.
I have adjusted that screw as as many times as the other adjusters in the gear case & the clutch lever.
You can see how this has became so frustrating for me, there just doesn’t seem to be any reason why this is happening after all these decades of it working fine & no solution to solving it.
I have a friend who is a very good engineer & even he can’t figure it out
I have been in my workshop today & for the zillionth time had yet another go at trying to sort the clutch issue.
I pulled the clutch plates out & put in another set of friction plates I have, I also took the gear case cover off & took that all apart, checked it all over, no problems there.
When everything was back together, pulled the clutch lever in, same issue, pressure plate travels too far out & only engages when the lever is almost fully released.
With the clutch disengaged I measured the gap between the pressure plate & the steel plate, the gap was 1/4", so you can see how much travel there is before the pressure plate actually presses onto the steel plate for the clutch to work.
One thing I have never been able to workout is setting the pushrod adjuster screw. The manual says screw in till the pressure plate just lifts then back off a 1/4 to a half turn.
From what I see for this to happen I have to screw the adjuster in quite far & turning it back by the desired amount still leaves the adjuster in contact with the pushrod, which can’t be good, no tolerance for expansion.
What I do is turn it in till it just seats then turn it back.
The other thing that there is no guidance on is how far to screw down the pressure plate springs.
I tighten them down till the studs are about flush with the head of the bolt,
make sure the pressure plate doesn’t slip when kicking over the engine & adjust to take out any wobble of the pressure plate.
Andy
As above, undo everything (slacken cable etc) then do the adjustment on the screw in the clutch centre. You should be able to feel when the screw touches the pushrod (don’t worry about lifting the pressure plate) when it’s touching then turn it out (away from the pushrod) about a quarter to half a turn. The adjuster will not be touching the pushrod when locked off.
Then, and only then, adjust the cable at the handlebar lever.
As for the pressure springs adjust until the top of the studs are at the bottom of the slot in the pressure nut. Then adjust by tightening the springs with the nuts as required to take out any wobble in the pressure plate. (This may involve tightening three rather than losening one).
The clutch drum that is fitted on my bike has the part # 57-1442, I have looked at the diagrams for both the 63 & 64 models & they both have this fitted.
What are the depths for a 63, 4 spring drum & a 64, 3 spring drum please ?
OK, with the help I have had so far I have made further investigations in to this issue.
From the diagram in the No. 4 book for a 63 4 spring pressure plate it states that there are 9 plates, 5 steel, 4 friction with the steel being first in place, which sits upon the lip on the inner drum, which mine has on it.
Both the No. 4 & my No.6 parts books state that the clutch drum has the
part # 57-1442.
I have measured the inside depth of the outer drum & it is 33mm.
The friction plates at their maximum measure 4mm, times this by 4 = 16mm
The steel plates are 2mm thick, times by 5 = 10mm
Therefore by my calculation the total clutch pack comes in at 26mm
This leaves a space of 7mm from the last steel to the top of the clutch drum.
How is all this sounding ?
If I remove one friction plate I am not seeing how this is going to make any difference to the issue of the pressure plate moving too far out & my problem remaining ?
The pushrod again in both parts manuals has the part # 57-1456, which is what I have in my bike.
With this extra information, does anyone have further help to offer please ?
Andy, the clutch basket or drum, wont make any difference to the clutch operation as long as the plates aren’t literally overhanging allowing the pressure plate to move.
The problem, as I see it, is the length of the pushrod compared to the thickness of the clutch plate stack. I have had a clutch centre that didn’t match the taper on the main shaft and therefore wouldn’t sit far enough onto the main shaft causing a difference in length.
I believe there was a difference in the number of clutch plates and the clutch centre when the design changed from a 4 spring to a 3 spring.
The issue seems to be a difference in the clutch centre/clutch plates/pressure plate total thickness and the pushrod/adjuster total length.
Assuming adjustment is done correctly then the pressure plate is being lifted too far on the operation of the lever. So, the whole clutch assembly is either too far into the engine due to the clutch centre pushing too far onto the main shaft (the teeth on the front sprocket and the clutch basket would then not be aligned so I very much doubt that) or there’s not enough clutch plates to take up the pull or the push rod is too long.
As previously, for the cost of a pushrod, I would cut one down by the length that it looks to need when you watch the clutch operating on pulling the lever.
I took my bike to a friend of mine whom is an engineer & has vast experience of working on old British motorcycles.
I was concerned about riding it over with the clutch issue, it turned out I was right to be concerned, the bike broke down around a mile from his workshop, the nut on the clutch centre drum came loose, had to do a roadside repair & made it to his place.
He spent over an hour going through it all & he also couldn’t find out why it is doing what it is doing, he also said it makes no difference whether it is 3 or 4 spring clutch.
He didn’t think the abutment & adapter in the gear case is a particular good design, to sloppy, so he designed a new mechanism, this is going to be sprung loaded & will pull the cable back when the clutch leaver is released, it is also going to be adjustable, complete one off, bespoke to my bike, looking forward to seeing it & how it works.
a quick question, when I rode my bike to my friends house on Wednesday, It would not go above 48 MPH at full throttle, is this also related to the clutch issue ?
At one point it was both dragging & slipping at the same time, weird as that sounds, that problem has now been sorted and the clutch works great apart from the problem with the travel of the pressure plate.
I did fit fishtail mufflers and there was nearly no baffles in them, so I fitted some, it was still way too loud so I wrapped those baffles with exhaust wadding which brought the noise level to a much more acceptable level.
Would this cause the bike to lose 50% of it’s power at full throttle?
my engineer made & installed the new clutch operating device into the gear case, it is fully adjustable and I now can set the clutch lever too any point that suits me.
It works flawlessly and has improved the gear shifting, it’s so much smoother.
I wish I knew how to upload photos too show what it’s like, next problem too solve is why the bike has lost 50% of it’s power at full throttle.
some parts of the above may therefore not apply as I don’t know my way around those clutches in any detail but I assume trhey should be basically alike.
