Kickstart Shaft Too Tight

A friend of mine just rebuilt his gearbox and now his KS will not return easily. He brought it to me for help, because I rebuilt mine successfully.
He seems to have excess friction in the shaft, even in the free-travel. Before I dig in to it, what is the most likely cause I should look for?
Thanks
Jaydee

Lack of end float or a binding bush/shaft if continuous, if intermittent eg only at certain angles then bent shaft is a possibility.

Over shimmed for the layshaft bearing.
Chose to use no gasket somewhere.
Did not releave the shims for the radius on the kickstart shaft where the shims reside.

pete.v said:

Over shimmed for the layshaft bearing.
Chose to use no gasket somewhere.
Did not releave the shims for the radius on the kickstart shaft where the shims reside.

Click to expand...

All good, or also the layshaft bearing is not seated fully in the case? Check for end float before digging in. It will provide more clues. Komando's comment about whether it is continuous or only at certain points of rotation would be easy to check before going in also.

Russ

I was putting together my gearbox tonight and ran across this problem. It is binding so hard that the kickshaft does not budge after installing the inner cover.

I have put all new bearings and bushes in.

I pulled all the gears back out and heated the inner case and using the old bush as a drift, tried to seat the kick shaft bush more fully in the inner case with my bench vise as a press. It did not appear to move as I was watching it closely. It is sitting a hair proud on the shell side of the inner cover, which I am guessing it should.

I heated up the shell with my heat gun, but I was afraid to do it too much as the mainshaft bearing and seal are also in, and using a socket as a drift I gave the layshaft roller bearing a few good whacks. I dont think it moved either.

I am using a SKF NJ203E 17 x 40 x 12 Roller and it went in very easily originally as I had froze it overnight and heated the shell in the oven. I did have to reheat the shell to reseat the mainshaft bearing, since I stupidly put the wrong bearing in there, but I made sure to tap the layshaft bearing.

I think it is sitting about 1/32 proud of the shell - is this normal, or does it need to go in more?

Edit: there are no shims on the ks shaft.

gortnipper said:

I heated up the shell with my heat gun, but I was afraid to do it too much as the mainshaft bearing and seal are also in, and using a socket as a drift I gave the layshaft roller bearing a few good whacks. I dont think it moved either.

I am using a SKF NJ203E 17 x 40 x 12 Roller and it went in very easily originally as I had froze it overnight and heated the shell in the oven. I did have to reheat the shell to reseat the mainshaft bearing, since I stupidly put the wrong bearing in there, but I made sure to tap the layshaft bearing.

I think it is sitting about 1/32 proud of the shell - is this normal, or does it need to go in more?

Edit: there are no shims on the ks shaft.

Click to expand...

Hi,

Sounds like the stars did not align on this job as often happens. I have only did four boxes so not as experienced as most of these lads but I usually put the lay bearing in with the shaft and you should be able to tell if the kick shaft bush is OK by the Paul and the way it rests on the assembly, but I am often wrong. But my boxes work OK after assembly if I take my time and the stars align .

jaydee75 said:

A friend of mine just rebuilt his gearbox and now his KS will not return easily. He brought it to me for help, because I rebuilt mine successfully.
He seems to have excess friction in the shaft, even in the free-travel. Before I dig in to it, what is the most likely cause I should look for?
Thanks
Jaydee

Click to expand...

Have it to bits for a look see , it's always good to help a pal.


Jg

auldblue said:

Hi,

Sounds like the stars did not align on this job as often happens. I have only did four boxes so not as experienced as most of these lads but I usually put the lay bearing in with the shaft and you should be able to tell if the kick shaft bush is OK by the Paul and the way it rests on the assembly, but I am often wrong. But my boxes work OK after assembly if I take my time and the stars align .


Jg

Click to expand...

No stars, just a big fat moon.

This is my first box rebuild, so I am in new territory. I put the lay bearing in with the shaft. Not sure how the pawl should sit, but it seems to move freely when hand-held in the lay 1st gear or in the inner cover. The gear comes about 2/3 of the way up past the kickstart pawl plunger.

I was wondering if it is possible to press the kick shaft bush in too far so the gear binds on the pawl carrier and doesn't contact the bush? But to my mind that would give too much free play wen bolted up, and not result in a binding of the kick shaft?

Also, how much can I heat the case and still have the sleeve gear seal be ok? I have seen layshaft bearings replaced in situ, with lots of heat and I am assuming the seals were not replaced on these, so maybe my fears are unfounded?

Hope these help, maybe .

Jg

Almost. Is that box open now?

It looks like the kick shaft bush is flush on the inner side? If that is so, then maybe mine needs to go in further, but I cant see how it could given pressed it fairly hard yesterday. Like I said, I can catch my nail on it as it is very slightly raised. And on the cover side, there is a very slight recess - I didnt measure it but I cant see it being more than .020-.030. But, if it was supposed to be flush on both sides, that would do it.


Hard to tell if the face of the 1st lay gear and the step on kick shaft that the plunger is in are on the same plane? It looks like this one may be a bit deeper in, but it is hard to tell. I will have to look at the interface here more tonght when I get home. But, again, I pressed this in pretty hard using the old bush as a drift in the big vise.

It all looks so easy in the video...

Hi,

The box is on my kitchen table if you need any photos , not a problem. I was howling drunk in Auckland at the Whitbread, what a morning!!





That bush is about 12mm in the shaft. Take your time and it will be easy.

Jg

auldblue said:

Hi,

That bush is about 12mm in the shaft. Take your time and it will be easy.

Jg

Click to expand...

I think I measured mine at 0.42" or about 10.7mm last night.

How far up out of the face of the shell side inner cover is the kick bush? Or how deep is it in the recess on the cover side that you have pictured?

Hi David, same thing just happened to me. Got the gears in then when I put the inner cover on, it would not go on all the way and the kick shaft was jammed. Took it of an d found I had rotated it into the engaging position and the pawl was stopping the shaft from fully going into place. i had not fitted the return spring at that stage and if it was there it would not have happened.

Dereck


btw, the kick start lever protrudes inside e cover exactly 1/2 inch.

sent you an email with same comment. let us know what you fpound

I can get the cover fully on. finger tight I can rotate the shaft.

The layshaft protrudes .95" beyond the face of the shell.

I get .49" to .52" from the face end of the KS shaft to the mating face of the inner cover.

I have .41" of depth from the face of the open end of the KS shaft to the face of the bush inside it.

I think I probably need to heat the shaft and drive the Bush home?

 

I would check to make sure the kick start shaft and the pawl are in the proper place..

gortnipper said:

I can get the cover fully on. finger tight I can rotate the shaft.

The layshaft protrudes .95" beyond the face of the shell.

I get .49" to .52" from the face end of the KS shaft to the mating face of the inner cover.

I have .41" of depth from the face of the open end of the KS shaft to the face of the bush inside it.

I think I probably need to heat the shaft and drive the Bush home?

 

Click to expand...

Is your trans still on the bike or did you remove it to do the rebuild? I had a similar problem years ago when I did my GB while on the bike, I had to pull the clutch basket, replace the circlip and re-shim it. For some reason it was binding up the gears when I went to re-install the cover.

Pete

Beach said:

I would check to make sure the kick start shaft and the pawl are in the proper place..

Click to expand...

With the the stud nuts finger tight I can rotate the kick shaft and feel the Pawl withdraw into the detent plate and extend out again and hit the stop the other way.

I heated up the GB shell so I could lift out the bearing with the hook end of a couple of Allen wrenches.


The bearing measures exactly the same depth as the one it replaced . 


Dropped it right back in and used a large socket the same size with a 10" extender to weight it down while it  cooled. 


Layshaft bearing was and is fully seated.


Bolted the outer cover on with the lay shaft  1st lay gear and the KS shaft. 


Still binds.


Must be the KS shaft inner bush is not fully in but I can't get it to move in further than .41".

Does anyone know how deep in the kick start shaft the shoulder is where bush bottoms out on?

Hi,

It could be the bush, it's not the first time I have had bushes that have been tight. I thought I measured it to be 12mm, So you are just over 2mm proud.
Jg

Just looked up the notes I made in 2011 when replacing my kickstart inner bush.
Not having measured the depth to the face of this bush before extracting the old one, I initially pressed the new one to a depth of 8.7mm or 0.34".
Naturally it bound on the 1st gear boss.
Re-pressed to 12mm (0.47"). All good.
Roller layshaft bearing. Kickstart shimmed.

On Friday I took the KS shaft in to an engineering shop near me that does a lot of frame work for Beezers here, and he pressed the bushing in. It gave a bit of resistance and then pressed in to 12.6 mm deep - bang on half an inch.

Assembled and shimmed to .005 - so all good.

Thanks, all!