920

Terry Prince says it will make well over 100 rwhp withou the need to rev past 6 k. How much over 100 is yet unkown as no other engine of this exact configuration has been built to date. His own Bonneville 1360 has most of the same parts but a bit higher comp and fuel injection.
It made 142rwhp on the dyno at 6500 rpm.

Glen

Dances with Shrapnel said:

Jim, you are saying "not breathing well" figuratively, not literally?

My understanding is that the reduced reciprocating mass allows the engine to accelerate faster as a result of:
1.) less inertial mass of the "lighter" reciprocating parts and
2.) less rotational mass due to the lower bob weight requirements and
3.) less translational mass to move down the track.

It has nothing to do with the term "breathing" as commonly used in reference to engines.

I thought Dave Watson did more to his engine than lighter pistons and rods.
Inquisitive minds want to know.

Click to expand...

Yes, "not breathing well" is figurative. And yes Dave Watson did add the JS stage 3 cam which is similar in valve action to his previous 7S cam. he 7S intake valve action is about the same as the JS3 but the JS 3 is symetrical and has much healthier exhaust lobe action than the 7S. So yes the JS 3 is hotter and that is part of the equation. The motor revs much more freely with the lighter reciprocating pistons and valve train parts and they gave him and additional useful 1700 RPM. He's pretty much cleaning the tracks in open vintage class now with Gary Thwaites in the saddle.

New JS cam profiles comparison chart here compliments of Jim Comstock.

http://www.jsmotorsport.com/technical_CamProfiles.asp

Gary leaning it below.

Good stuff Jim.

If you can take a call tomorrow I want to chat a bit about some stuff.

Another factor of lighter pistons/rods is their lesser mass for less acceleration jerk forces that can tear apart at higher rpm. Jim here has bested everyone in lightest pistons as he's drilled and milled his own beyond out of the box offerings. So a win win, allows higher rpm and tougher too.

Hi

Just for your info. My engine is Dave Watsons ie Garys engine from a few years ago. The spare & just not used much, so he sold it to me

Chris

Chris said:

Hi

Just for your info. My engine is Dave Watsons ie Garys engine from a few years ago. The spare & just not used much, so he sold it to me

Chris

Click to expand...

What frame is it going into? Have any photos of the project?

Hi Jim

Its in the orange mk2 Seeley.

Chris

The orange seeley looks fantastiic and very trimmed down. I hope you can afford to get the JS lightweight pistons/rods in it someday. It will transform the bike.