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Tech Information => Technical Discussion => Topic started by: F-Head on July 17, 2017, 04:20:14 PM



Title: Motorcycle tech question.
Post by: F-Head on July 17, 2017, 04:20:14 PM
Two tech questions from a newbie please.

I plan to build a motorcycle in the pushrod engine class; M-PG or A-PG.

1. Can I use aftermarket or modified cases, cylinders and heads?
2. Can I alter the bore and stroke provided I stay within the class capacity limit?

Or would these changes require entry into the 'Modified' engine class A.
I know vintage pre 56 entries must use the original (or close) parts but am unclear about 56 on.
I've searched through the book but can't find the answer.

Thanks for any help, Ian 


Title: Re: Motorcycle tech question.
Post by: Stainless1 on July 17, 2017, 06:49:26 PM
SCTA event or BMST?


Title: Re: Motorcycle tech question.
Post by: F-Head on July 17, 2017, 11:59:53 PM
BMST but from reading both their rule books I thought the specs were the same?
All help appreciated, thanks. Ian


Title: Re: Motorcycle tech question.
Post by: Frenchinjection on July 18, 2017, 06:30:22 AM
F-Head, our bike is APS-PBF 750.  It has billet head, rods, crank, block, gearbox, and cases.  It's still a pushrod.


Title: Re: Motorcycle tech question.
Post by: F-Head on July 18, 2017, 06:58:39 AM
Thanks Frenchinjection.

Did you seek clarification or just go with the rule book?
And did you change the bore or stroke, or stay with standard?

Thanks, Ian


Title: Re: Motorcycle tech question.
Post by: comet on October 25, 2017, 01:57:38 AM
How did you get on Ian?
I always assumed (dangerous thing to do) that the heads had to be as standard from the factory so I am curious to know the answer on this.

cheers
John


Title: Re: Motorcycle tech question.
Post by: Koncretekid on December 23, 2017, 09:54:32 AM
Ian and John,
I was just perusing some older posts and noticed this one that never got fully answered.  I don't have my rulebook in front of me but the only restriction that I'm aware of is that you can't change the number of valves in the head.  The head on my 500/600cc APG and APS-PG has been highly modified and in the 500cc version, the bore and stroke have been changed to remain under the class limit.  So a Westlake 4 valve motor is legal because it was made with 4 valve head, but I don't believe I can put a Westlake 4 valve conversion on my BSA single.  A Triumph 750 twin should be legal with the very late model ('78?) 4 valve head but you'd want to confirm that with tech.  I have only run AMA events so am not sure about SCTA on this rule.
Tom


Title: Re: Motorcycle tech question.
Post by: Frenchinjection on December 28, 2017, 12:50:36 PM
If it is in the A class then you can do pretty much what you like. 


Title: Re: Motorcycle tech question.
Post by: **RP** on January 04, 2018, 10:27:19 AM
SCTA allows 8 valve head on a Triumph in M or A frame - pushrod engine since it was a production head on one model one year.  At least a few records were set with them in the past.