KT100 Jack shaft question

Not a bad idea. Yamaha cranks are kind of prone at breaking at the keyway and a third bearing support will reduce the likelihood of that happening.
 
I can't imagine why that would be necessary. Still, it can't be any worse than with a clutch. On the other hand, I've never heard of anybody breaking a crankshaft running direct drive without a 3rd bearing. True, not much information in regards to that. I raced KT100 before the 3rd bearing was made necessary, with a clutch, and never broke crank. I would imagine that a 3rd bearing set up puts a lot less strain on the crankshaft.
 
F1F21,

Will you be running the clutch on the jack shaft? Chain or belt back to the jack shaft?

Many years ago for road racing (where we were typically using an axle clutch), I built my own Yamahas with an old "straight shaft" PTO crank half (combined with the modern tapered ignition side crank half). This allowed getting the belt drive pulley right up tight against the case, instead of having the pulley outboard a fair bit more to pick up the taper and keyway on the regular crank.

FWIW...

PM
 
If I'm not mistaken, I believe the 3rd bearing support was designed a while back for supporting the heavy oil filled Horstman & L&T clutches. Not really needed for the chain or belt drive on a jackshaft. Unless your track has a lot of rocks. Then you might need it.

Brian #89
 
Pete_Muller said:
F1F21,

Will you be running the clutch on the jack shaft? Chain or belt back to the jack shaft?

Many years ago for road racing (where we were typically using an axle clutch), I built my own Yamahas with an old "straight shaft" PTO crank half (combined with the modern tapered ignition side crank half). This allowed getting the belt drive pulley right up tight against the case, instead of having the pulley outboard a fair bit more to pick up the taper and keyway on the regular crank.

FWIW...

PM
Click to expand...
I’m running the on the Jack shaft output side.
 
If it doesn't hurt anything or slow you down use it because one DNF is worth a ton of wish the heck i'd of used it.
 
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