When is it advisable to beef up the stock crank. At what level of torque or horsepower? Just wondering?

 

Any time is a good time to build up stock crank.
We have put about 125 hp on stock with blowers no probs. Also long as you dont beat the sh@#$% out of it. your okay. But what fun is that if you cant beat on it LOL.

We would like to see them all done from the factory would be nice.

But we like to say about 120 125hp then it time to beef it up. Than you you are pushing it.
But the new bikes the day they come from the factory.
My 2 cents.

 

We also use 120 as the number and the older cranks were pretty reliable. The newer cranks are all over the place. The bike in my sig. has a untouched crank in it and it does get beat on but it came with the Timken bearing.

 

if you are going to do rolling burn-outs, hole shots, wheelies, get it sideways, or generally having to much fun on a harley you need to get the crank worked--especially on the newer bikes.

 

If I ever split the cases I would do the whole thing. Crank and Timkin bearings upgrade.

 

Why is the tapered(Timkin) bearing considered an upgrade? Why wouldn't a high quality straight roller be just as good if not better?

 

A straight roller bearing eliminates the need for setting bearing endplay, which significantly reduces labor costs during assembly which is why the MoCo made the change in '03. However, a straight roller bearing cannot handle the thrust and the high loads generated by upgraded engines producing more TQ/HP than the stock engine was designed to produce. Once an engine reaches approximately 100 horsepower or more, normal crankshaft flexing at high speed can fracture the straight roller bearing's outer race. When that happens, broken bearing fragments fall into the flywheel cavity and end up circulating with the engine oil, destroying engine components and sometimes leading to catastrophic engine damage. Not a mechanical engineer but JMHO.

 

How about That...

 

So is this issue Harley Davidson specific? Is this only an issue to the stock bearing? Will an upgraded straight roller bearing stand up to the abuse of higher HP? I'm not trying to bust your *****, just trying to get a handle on the why's of a straight roller bearing vs a tapered in this application.

 

I ran across this looking into crank issues a while back. http://www.youtube.com/watch?v=9uh9FVm3Hv8