Burman 52 gearbox - clutch issue

[G3L1946]

Good evening all,

In a nutshell. I’m unable to select any gear as, when I try, the gears ‘ graunch’ and fail to engage. I used to get a pleasant ‘clunk’. All new clutch plates (excluding the plain steel ones which are O.K.).
Thrust rod is the correct length and ball ( ball bearing) is at the correct end. New ,correct, clutch cable. Five new pressure springs. I can (just) adjust the cable to allow for the correct amount of play at the gearbox end adjuster. Plates are moving with no apparent obstruction and at the same rate.
Springs adjusted as per manual. Clutch set up as per instructions in manual. I even replaced the old, worn, clutch plates but still the same
I’m now at a loss! If I try to extend the adjuster to allow greater ‘pull’ the rotary clutch lifter mechanism overrides itself so it would appear the mechanism itself is not at fault. It can be seen that the actuator rod is moving correctly.
Photos of cable adjuster , clutch, old and new plates.

Matchless G3LS 1955. Burman 52 gearbox.
Help!

Steve

[SPRIDDLER]

G clutch 2.jpg

It may be your photo but all the springs should be screwed in an equal amount.
If you operate the kickstart with the clutch 'free' (h/bar lever puled in) all the plates should rotate in the same plane without any 'wobble'.

The cable adjuster should be adjusted to give about 3/16" free play at the h/bar lever. If this is achieved and the balls override their ramps you haven't adjusted the thrust rod correctly (sufficiently). You say you have adjusted it to the manual instructions. This must be done with plenty of free play/slack in the cable or preferably with the cable nipple disconnected from the clutch operating arm.

[G3L1946]

Hi Spriddler,

There is a slight difference in amount of stud protruding for each spring. This is unavoidable due to the amount ( four ) turns out from fully closed. Four turns of each spring adjuster results in this difference. In short, each spring is equally screwed in ( more accurately, out from fully closed up ) and under the same tension. They are all new springs.
There is about 3/16 play at the lever, handle bar end with cable ‘lift’ from gearbox end of about 1/8 ins. This is within the prescribed limits. With this set up there is no ‘over run’ of the ramps.
Tried setting with complete slack on clutch cable and with cable disconnected at the mechanism end.
Plates open at the same rate ( equal amount) with no wobble.
Just can’t seem to get it right after different pressures on springs, variations on centre nut and using additional ball on basket end of rod ( ball each end, not as manual but a recommendation). Adjusted in the right sequence.

Thanks,
Steve

[SPRIDDLER]

There is a slight difference in amount of stud protruding for each spring. This is unavoidable due to the amount ( four ) turns out from fully closed. Four turns of each spring adjuster results in this difference. In short, each spring is equally screwed in ( more accurately, out from fully closed up ) and under the same tension. They are all new springs.

I may be misunderstanding but I can't see how four turns out can result in the nuts being in different positions, because:
If the springs are all of equal length and the spring cups are all of equal depth an equal force on the pressure plate must be with all the spring nuts recessed or protruding the same amount as each other. The length of each the five studs is irrelevant, but they should all be the same length unless any of them aren't fitted in the back of the basket with the 'flat' on the head against the radiused boss on the rear of the basket (- difficult to explain).

I've never used the 'four turns out' method. I always start with all nuts flush with the pressure plate, then if it slips I tweak each one in maybe a quarter of a turn. In fact I make any necessary tweaks by putting the front wheel against a tree with the engine running and try to 'pull away' in 1st gear with normal 'pulling away on a hill' revs and can normally unscrew them a bit which reduces the effort needed on the h/bar lever. I can operate the Burman clutch on my '54 G3LS with my little finger. I have to, as I have the clutch and front brake levers one above the other on the left of the h/bars. Regardless of the manual I suggest that you equalise the nuts so that they are all flush with the pressure plate and see how it performs.

[SPRIDDLER]

The length of each the five studs is irrelevant, but they should all be the same length unless any of them aren't fitted in the back of the basket with the 'flat' on the head against the radiused boss on the rear of the basket (- difficult to explain).

You can check whether any of the studs isn't fitted correctly (i.e. isn't fitted with the 'flat' in the correct position) by removing the springs and cups when each stud should be free to flop about. If any of the studs have trapped heads it will be held rigidly in place and won't flop about.

To clarify my mention of both levers on the left of the 'bars, front brake above clutch lever............

2020-05-11 K lever cable swap 011 (640x425).jpg

[clive]

If one of the studs was not wobbly as described by spriddler then it would engage with the clutch basket. With the engine running this would result in drive still being imparted to the clutch centre and hence grauching when you try to change gear. Well worth checking.
I often have to have one or more of the clutch spring nuts turned in or out more than the others to get a flat pull on the pressure plate but yours do seem to be a strange pattern 3 out 2 in. Normally i have to adjust it so one is out and the ones either side of it are out but rather less to get the flat pull.

[G3L1946]

Morning Spriddler and Clive,

Firstly, the studs are free (wobble) and all equal in length. The only way I can understand the difference would be that when tightening down I’m inadvertently not getting each one exactly to the same level of tightness ( bit difficult to explain ). Common sense would dictate that all should achieve the same travel if the start point is the same. I will re-examine. Today, I will readjust the springs so all studs are flush and try again. With reference to play at lever end. There is no way I can adjust at this end with all adjustments being achieved at the gearbox end. However, as it happens, the play either end are as required and stated by Spriddler. I’m surprised that do achieve this the adjuster is practically all the way out with very little of the threaded part located ( see photo ).
If the problem persists it may be an idea to undo each ‘nut’ a couple of turns and retest to see what that results in. Any other ideas you might have, much appreciated.

Regards,

Steve

[dave16mct]

Are you sure you slackened the cable right off before you adjusted the thrust rod? (The screw and locknut in the middle of the pressure plate.) Then slacken the locknut, screw in the adjuster until you feel it against the thrust rod. The back off 1/4 to 1/2 a turn and tighten the locknut without moving the adjuster. Then adjust the cable.
Dave

[G3L1946]

Hi Dave,

To the letter! That’s why I’m running short of ideas! I followed the adjustment sequence diligently
on each occasion I tried the various options.

Steve

[SPRIDDLER]

As you/we have assumed, the most likely reason that the gears are graunching is because the plates aren't freeing.
Time to go back to basics.
Has the clutch ever been O.K. or did you obtain the bike as a non-runnner or boxes of bits?
What prompted you to replace the clutch (friction) plates?
When you pull in the h/bar lever can you see the pressure plate lifting?
If you hold in the h/bar lever and operate the kickstart (in Neutral) does the kickstart depress easily with virtually no resistance nor turning of the engine ?