Primary run out

[coater87]

 When I built my clutch from Suzuki parts, I discovered at that time my main shaft was cracked.

 I had a spare shaft, and finished the gearbox using that one.

 I noticed wobble in the clutch basket. After putting an indicator on everything and spinning, the shaft has .004 thousandth run out, which equates to .022 run out at the sprocket teeth moving side to side on the clutch.

 Anyone have an opinion on this amount as far as usability?

 I doubt the original was dead nuts, but I have no clue what a decent  go or no go figure should be.

Lee

[chaterlea25]

Hi Lee,
It is not uncommon to find the shafts "bent"
I have often wondered how this has happened, Broken chains? or gorilla armed owners hammering on the clutch nut??

Anyway the shaft should run absolutely true !
I have straightened one or two that were only a couple of thou out 
Your side to side movement seems a lot? maybe the better bearing ?
Does the chainwheel run true with the clutch disengaged?
Usually when the shaft is running out of true you will see the primary chain tension changing as you turn the gearbox over with the clutch pulled in
The bend is usually at the clutch end of the mainshaft

John

[JulianS]

I would be concerned that an out of true mainshaft would cause premature wear to the large mainshaft ball bearing and to the sleeve gear bushes.

[coater87]

 OK,

 Here is what I am going to do.

 I ordered a new main shaft from Degroot.

 In the mean time I am going to investigate the current main shaft further, and try to figure out exactly where the bend is. I will try to heat straighten it, if that gets it close enough I will use that shaft in the spares box. If I cannot get it straight, nothing is really lost.

 I know what you are saying Julian, running a bent shaft is hard on everything. The box has all new bearings and bushings, it would be a bit of a shame to run with a bent shaft, its not like I have to have one custom made.

 I would think the only way these could get bent is by owners over tightening chains. You have the primary pulling one way and the drive chain pulling in the exact opposite direction. Maybe add in a good blow or two from a lump hammer while it is under that kind of stress and there you go- bent shaft.

 Lee

[chaterlea25]

Hi Lee,
I have watched Keith Fenner  heat straightening marine shafts on you tube
Thats quite a skill

I used a home made jig that has a Sykes pickvant hydraulic puller jack as the mover
it gives enough feel to do delicate jobs
some Vee blocks and some copper pads and work away

John

[coater87]

 Hi John,

 The biggest hurdle I can see with heat straightening this shaft is the fact its hollow. I have no idea if its going to act "funny". Will it pull straight back towards the heat, or will it do one of those "S" kind of things and end up more like a corkscrew.

 Either way, old shaft is out, new shaft is ordered.

 The goal this year was to get the bike mocked up and running. I would send the tins out to be painted over the winter. If thing continue with 2 steps forward and 5 steps back, that may be unreasonable.

 Lee

 

[orabanda]

Hi Lee,
As John said, use a press, but don't heat.

[coater87]

 You guys have failed at the heat?

 I think I will just skip that entirely then, and follow the plan of just trying to press it back in.

 Lee

[KiwiGF]

You guys have failed at the heat?

 I think I will just skip that entirely then, and follow the plan of just trying to press it back in.

 Lee

I reckon the original shaft was made out of kryptonite and heat would have no effect anyway, I found this out when trying to remachine the thread on the gearbox end (after repairing a split with silver solder and getting it red hot). The shaft/thread was still glass hard even after being heated red hot and left to cool slowly and several carbide machine tools and eventually files were blunted trying to clean up the soldered thread 

This also might mean bending it straight might be tricky.....if it's more brittle than ductile.