270 degree crank

mdt-son said:

Jim, I am most impressed. Will you provide a Mk3 version as well?

Do you have weight and moment of inertia (I_max) figures for both versions featuring an 89mm stroke?

Cheers, Knut

Click to expand...

As with the Maney cranks - you just shim the main bearings to fit the crank to the Mk3 cases. But you could special order a MK 3 specific crank. The weight is approx the same as a stock crank. I don't have the detailed moment specs. I think the 360 deg crank in the photo above is in Yves Seeley now. See Yves thread "anyone as experience with 920 engine".

jseng1 said:

mdt-son said:

Jim, I am most impressed. Will you provide a Mk3 version as well?

Do you have weight and moment of inertia (I_max) figures for both versions featuring an 89mm stroke?

Cheers, Knut

Click to expand...

As with the Maney cranks - you just shim the main bearings to fit the crank to the Mk3 cases. The weight is approx the same as a stock crank. I don't have the detailed moment specs. I think the 360 deg crank in the photo above is in Yves Seeley now. See Yves thread "anyone as experience with 920 engine".

Click to expand...

And I am very happy with your crank, thanks Jim

Jim, in one of your videos you stand a featherbed Norton up on it's back wheel on the throttle. How does that happen - has it got all your good bits in it ? Or is it simply geared strangely or have a different weight distribution from normal ?

acotrel said:

Jim, in one of your videos you stand a featherbed Norton up on it's back wheel on the throttle. How does that happen - has it got all your good bits in it ? Or is it simply geared strangely or have a different weight distribution from normal ?

Click to expand...

Its a test bike for all the JSM products. It has the lightweight pistons, longer rods, JS0 cam kit (near stock lift and duration but with lightweight lifters), Beehive springs gapless rings, reed breather. So its very efficient. Some extra power comes from 1-1/2" free flow pipes and longer intake manifolds with 32mm carbs. All these things are street friendly and it still has the low end grunt. The top end and wheel lifting power comes from the Axtell port shape (with a little cobra head shape thrown in) - details I learned fro racing. It has the tall gearing equivalent of a Commando with a 23 tooth and it is stripped of weight like a racer except for the lights. It does 100mph at 1/2 throttle and approx 130 wide open tucked in. Yet its completely comfortable on the freeway at cruising speed. It amazes me everytime I ride it and I put as many miles as I can it.

I have always found that with a featherbed, the rear wheel will usually spin before it will pick up the front wheel. Have you got a gap between the mount on the front of the engine casings and the mount on the front down tubes of the frame ? Perhaps I had harder compound tyres ? Regardless, your bike is very spectacular when it does that. I've never seen that type of bike do that previously, even off the start grid during races when the guys rev the tits off their bikes and drop the clutch.