ET: Engine (Twin) Stripped Splines on Kickstart Shaft and Lever (Weep)

[AndyBee]

Hi again,

Andy in Lincolnshire (UK here). So, in a stunning sequel to my other newbie question today, while attempting to learn the correct starting procedure for my newly-acquired 1950 Black Shadow today (holding the decompressor in 'til the bottom of the kick) I managed to strip the kickstart splines. Looking at the shaft, I think it was already in a pretty sad state when I got the bike (pic below). So I guess I need to get myself a new kickstart shaft and lever. Before I do this I wondered:

1. Is it okay just to drill and bolt the lever and shaft? Is this a thing?
2. Is there anything I can do to prevent the same happening to the new hardware? The splines look pretty fine/thin to me.
3. Is there some sort of upgrade/improvement I can do?
4. Does anyone have a link to a good resource to help me change the shaft?

I'm still feeling a bit sad and forlorn about the broken starter assembly, so I'd better fix it pronto to redeem myself!

thanks and best wishes to all,
Andy

 

[royrobertson]

Hi Andy, You could drill a hole longitudinally half in the shaft and half in the kickstart say 5 -6mm diameter, at 90deg to the split, once you set the kickstart at the required position and fit a hardened dowel. A similar modification lasted 18 years on my Norvin until I sold it in 1984. I also found that undoing the bolt and with careful prising the kickstart could be removed and refitted. Instead of drilling, which I must admit is tricky, there is always spark eroding.
roy the racer

 

[Len Matthews]

I'm not sure if he still does it but Ray Elgar was able to reform the splines in kick start cranks he did one for me.

 

[Bill Thomas]

The kick start is a hell of a price,
So Roys idea sound good,
But if you have to buy a new shaft, Go for the longer one, That helps to miss the Exhaust.
The normal splines are OK , But you must keep the pinch bolt tight !.
Good Luck, Bill.

 

[chankly bore]

Some Panther owners have posted about carefully drilling and fitting bearing rollers of about 5 to 6mm. diameter.

 

[oexing]

Andy, don´t feel bad about the stripped spline - not your fault, it was never ever a great idea to pair a spline with a pinch bolt and slotted lever. This never was a joint on any other brands as well that held up on kickstart levers at brute forces. Look at push bike pedals - or Guzzi classics or BMWs : No splines but taper bolts acting on flats milled on the shaft. Some British gearboxes used same design, SA or Burman possibly.
I was lucky to have one of two B Rapides come with a stainless kickstart lever, so one job - and worry - less to have it chromed finally. Certainly splines and shafts were scrap from Argentina, so my decision was the pushbike pedal mod. The slotted end was binned and a stainless cap welded on the lever for getting the meat there for the taper bolt. So no splined shaft was needed, just a new shaft splined and brazed into the gear segment, the flat waiting to be milled as I am still far from trying position of lever with bike on wheels.
Another easier repair is having the lever slotted end cut off and welded shut for a square through hole to be wire spark eroded, best with square sides one degree taper cut - every day wire edm job in toolrooms concerned with sheet metal cutting/forming.
The kickstart shaft then gets its one degree taper square on the dividing head on the mill, no miracle to do, just take your time. Best to have a shoulder as final stop on the taper square else you´d have trouble to get the lever off with excessive force. So test the fit of taper by push the lever on the shaft with finger, check depth and bolt up as hard as you will do later. Take another depth check in this position and remember to have this difference for distance from final step on shaft. So in the end you get a suitable fit on the kickstart shaft that lasts and can be taken off with acceptable force - depending on your chosen bit of final pull up to the step. In this design you have a bolt and big washer on the shaft end for pulling the lever up the taper and keep it there. This would be the Horex design postwar. Yes, you cannot set fine positions of lever like with the splines, so you mark sides of square as you like them. But with BMWs, Guzzis and all , for many decades there was never a big discussion about setting lever positions, no real need, once an acceptable average was set. . . . . and there was never discussions about stripped splines and scrap levers from this as well . . . .

Vic

. . . . yeah, no rubber on lever : Recently I did the gasoline soak trick on tough Guzzi foot rest rubbers - worked like a dream, no sweat at all. Just accept stink for a few weeks till fuel has evaporated completely :

 

[Peter Holmes]

A good spline mated to a good shaft will last the life of the bike if the pinch bolt is tightened correctly, and checked for tightness now and then, and the kickstart is infinitely adjustable for the desired position, which none of the alternative bodges are, although once the splines are wrecked they might get you out of trouble as a temporary measure.

 

[oexing]

Obviously this pinch spline idea does not last forever, fact is, only a few splines closest to the slot carry all loads, so over time they fail , starting from the slot and advancing around till failure. The splines prevent forces from the pinch bolt to spread around the whole spline logically. So there the logic gap in this. Pulling up the pinch bolt just takes up wear in splines near slot walking around till failure. Anyway, restoring all parts to standard splines is a biiig job unless you buy all new. And you´d be challenged to find a shop to do it today. This is the most complicated repair you could go as alternative to my samples.

Vic

 

[Peter Holmes]

OK I concede, nothing lasts forever, not even cotter pins, but I purchased my Rapide in 1965 and it is still using the original Kickstart lever, so 57 years so far, and no sign of getting worn out yet, kick start spline sheering is not a regular topic of conversation on this Forum, so I would assume that I am not alone in finding the standard set up to be highly successful and reliable. Your solution is taken from the older cycle world, but no longer used there, apart from on the very cheapest cycles, we referred to them as cotter pins, and the nuts that held the cotter pin tight to the bottom bracket shaft needed to be checked and tightened frequently else they loosened and mangled the cotter pins and the pedal cranks came loose, in my opinion a ghastly solution to a problem that does not exist. It is of course essential that the male and female splines are a very close fit when the pinch bolt is loose, ideally requiring a firm push to engage the two, once that is achieved, and the pinch bolt tightened, the set up will last a very long time, for me 57 years and counting.
But if your starting point is a worn spline on both components, then no amount of tightening the pinch bolt will solve the problem.

 

[ClassicBiker]

Actually back in the 80s my father bought a brand new kick start shaft and kick start lever from one of the well know suppliers and after three kicks it stripped, in spite of being tightened right up. So he made up a rather large fitting and pinned it to the stripped shaft. That lasted for a few years, till the shaft snapped on me. So I have no faith in the fine splines on the Vincent. The spines on my unit Triumph 500 are far courser as are the splines on my 125 Yamaha. My answer to the stripped splines was to make my own kick start shaft from 4130, 0.25" longer to clear the exhaust. I positioned and marked where the lever would be most comfortable for myself. I then put shim stock around shaft placed the lever back on and drilled two 0.1875" holes parallel to the axis of the shaft half in the lever half in the shaft at what would be top and bottom when on the bike and a further 0.25" hole at what would be the rear. I then hardened the shaft and installed on the bike and placed dowel pins in the holes. When clamped down there is no way it is going to move.
Perhaps what is available as replacement parts now is better than it was in the 80s, but back then it was rubbish.
Steven