Clunky gear change after rebuild

[roadrocket]

Hello

I rebuilt my engine and box last summer, and have done 300 miles on the bike. The gear box clunks when changing, in just about all gears. Neutral to first is worst, but all gears have some clunk. Under way I can sometimes change between 3rd and top without any trouble. All gears engange quickly and without any other trouble than the clunk. I can select neutral at standstill without difficulty. I have adjusted the clutch, and have a 4 springer with an SRM plate. All bearings and bushings in the box are new, and the actuating arm was sleeved. Detente spring is quite loose now. Primary chain too. I have tried to disengage the clutch with a cable tie, while rotating the rear wheel, and changing gears. Audible clunks when changing all gears. This is annoying as I have had a smooth silent box before the rebuild some years back, before a locked up cush drive shattered everything in the box. I guess the clunks come from the gears themselves, and I feel a smack in the lever when changing by hand.

What can be the cause?

Otto in DK

[madsens]

Hi Otto
A bit off topic - did you make the sleving of the Clutch arm yourself? I have same job ahead, and trying to find somebody to help me out...

Regards
Joergen

(app. 7km from you 

[roadrocket]

We should meet! The always friendly Bendt from the Club made it for me. And helped with assemling the whole bike after the rebuilt engine came back from Horsens.

[duTch]

 Sounds kinda normal really, only thing I can think of, is the final drive chain tension...?
Otherwise, do you use the throttle when changing..? I ride mine like it's between an old truck with a crash box, and a GP bike,  *eek*and match the gears with revs....

[roadrocket]

Dutch; well it didn't use to be like that. I was used to fast positive changing without any noise at all, much better than my 1986 BMW with its inherent "clack".

[muskrat]

I agree, our g/box's are pretty bullet proof and if set up right should change quite well. Most culprits are clutch, detent spring, and indexing. A worn camplate or selectors can give trouble. That reminds me, did the selector forks go in the same way? They are both the same but can wear into a groove and if swapped over give problems.
My '57 box handled 9 years of racing with only the very occasional oil change.
Cheers

[The Artful Bodger]

Hi, if it's worse neutral to first sounds more like a clutch issue. When the box isn't turning when the bike's stationary and clutch is in, the only thing that can cause a clunk is clutch drag. The effects will be less once the box is turning via the back wheel, certainly going up the gears but probably worse when going down the gears unless the throttle is blipped to get a bit of a speed match.
 Colin

[roadrocket]

Bodger; will have a second look at the clutch. Muskrat; I am not sure which way the forks went in, but I have three sets, so something to experiment with. I also have a spare cam plate and quadrant. However, I don't seem to have any clutch drag, as I have no pull while stationary in first with clutch disengaged, I know how that feels! But Maybe I should look at the plates even though spring tension seem ok, maybe they stick for some reason.

[Gerry]

Hi Roadrocket, I have the same problem and maybe a bit worse as I cannot select neutral without difficulty when stationary and selecting first is quite clunky. What I have noticed is that with the clutch plates removed turning the inner drum is not as free as I would have thought it should be (four spring clutch) and a friend has told me that if the rollers are not correct they could be tight against the drum causing the drag. He showed me some rollers and using a mike there was a difference of from 0.001" to 0.004" in their length. So I am going to remove the inner drum and check this out. Will let you know what transpires. Cheers. Gerry

[duTch]

 Hey Gerry----haha I ain't stalkin'....I have a feeling that others can verify or not, that later clutches should use what are I think commonly known as 1/4"x 6mm (maybe "6mm" being something like 15/64"), so possibly a previous owner (PM), used 1/4" x 1/4" instead- just a fly crap or two longer- 1.5thou.....just a wild guess....

[unclerob]

I had a very similar problem on a bike I bought a couple of years ago which had a rebuilt clutch and gearbox but 'clunked' badly when changing gear. To cut a long story short the problem turned out to be not exactly the clutch dragging but being momentarily slow to disengage as it were, just enough to cause gearchanging problems....
Once I finally got round to pulling it apart I found the plates had a sticky residue on them....a mixture of rust (from standing unused for a long while) and too thick oil....a thorough cleaning and the right oil improved things enormously!

[wilko]

T'was obvious from the start that it was a grabbing clutch ??

[unclerob]

No, it wasn't grabbing....just (I think) disengaging slowly! If you changed gear normally it would clunk into the next gear, if you pulled the lever in, waited a second, then changed gear....it was fine. I spent a fair bit of time adjusting springs to get it to release evenly but it was only when someone here suggested a thorough clean of the plates that the problem was solved...so I'm assuming that what was happening was that whilst the clutch was engaged the plates were tending to stick together a bit and the extra effort of breaking that sticking as you pulled the lever in was enough to spoil the gearchange?

[wilko]

 Grabbing, sticking, guess it can't be the clutch then.

[edboy]

although i am not dismissing a worn clutch or a loose mainshaft i always associate clunky gearboxes with a lack of oil in them. if the box is rebuilt correctly and the oil level correct perhaps try a thicker oil .if still no good you really have to try and pinpoint the source by finding the wear in splines, dogs , bushes or bearings.