Bring a Production Engine to class size (Bike)

[wfojohn]

I have the 2013 rule book and am referring to page 133, section 7.J.1 under Engine Classes. I need some clarification to be certain I understand the Production Engine rules correctly.

Production Class - The Bike left the factory with 398cc. To obtain 499cc and be at class limit of 500cc only boring the cylinder will not provide anywhere near the maximum class limit so Stroking the crank in addition to boring would make class limit or reasonably close to it. Stroke change and overbore while still using oem case, cylinder and head will be possible.

Is this legal or have I missed something restricting the engine to stock stroke? This is only about Production Class.

Thanks,
John Ritter

[Jon]

Engine mods that aren't visible are legal in production class.

Cheers
jon

[wfojohn]

Jon,
I thought so but stroking a Production class engine just seems sooo wrong to me. Thanks.

[dw230]

What did the SCTA m/c tech say?

DW

[rouse]

Keep in mind that if you stroke the engine, you can't run stroker plates under the cylinders ( they can be seen ), So how you make it fit is up to you, it just can't show.

I heard that for the horses mouth.

Rouse

[wfojohn]

Rouse, we commonly use plates but they are visable. I really don't have an answer for that unless the engine having it done can utilize a different rod  and piston with a pin position that would allow the setup. I know John Noonan will have Wossner make a couple special pistons and the price is reasonable. I did not have any specific engine in mind when I posed the question. This all came about due to a spitballing session with my son and I said from reading the rules I thought it might be legal, neither one of us think anything other than a .020" overbore should be allowed in Production but hey the rules rule. Thats just our one-sided opinion, we are not trying to change anything. Thanks to all for the feedback.

[Stan Back]

I'd guess, in a way, it could kinda level the playing field in a particular class between the manufacturers.

(Like having 597cc, 599cc, 640cc and 650cc all in the same class.)

[rouse]

Rouse, we commonly use plates but they are visable. I really don't have an answer for that unless the engine having it done can utilize a different rod  and piston with a pin position that would allow the setup. I know John Noonan will have Wossner make a couple special pistons and the price is reasonable. I did not have any specific engine in mind when I posed the question. This all came about due to a spitballing session with my son and I said from reading the rules I thought it might be legal, neither one of us think anything other than a .020" overbore should be allowed in Production but hey the rules rule. Thats just our one-sided opinion, we are not trying to change anything. Thanks to all for the feedback.

All it takes is $, and lots of it at times if you want to change the stroke and not have it show on the outside. Bore is easier but then you still have to have new pistons. But then them OEM cylinder will only take so much.

That's why it's fun, if it was easy......

Rouse

[wfojohn]

Moving the crankpin (press together crank), fly cutting a bit of clearance in the cases, CWT computer balancing the rotating assy, boring, modifying the rods etc are things I have the equipment and experience to do, everthing in house except nikasil. We have a dyno room with a Land & Sea computerized engine dyno and Superflow bench but like you said who has time. The rule still has a bad gut feeling to it.

[fredvance]

Been that way for a long time!!

[rouse]

That's what keeps it fun. If it fits the class requirements and displacement limits, go for it.

I think that the rules are restrictive enough as they are, P and PP bikes can be verified using sales brochures from the manufacturer, why should a tech inspection have to go further than that.

SCTA has it right just like it is.

[Dean Los Angeles]

Production is "stock appearing". What you do to the internals is wide open.

[grumm441]

I had a shit fight at Lake Gairdiner this year with two production bikes that were the same only different and one vintage class bike that was claimed to be production but didn't have lights or a muffler.
The main thing is that it must look production. so no visible modification
I think we (Matt) kicked about five bikes out of impound last year for things that were not quite production and there
should possibly have been one more that left impound to be put in the bike tech trailer overnight.
so you can do what you want inside the engine as long as it looks like it looked on the brochure
also, as I understand it, you cannot run in a production class with a bike that is bored greater then the capacity for the class it is running in
G

[wobblywalrus]

John, a picture of your piston from the side, the rod length, the bore, and the stroke would be helpful.

[wfojohn]

Wobbly, the original question was to make sure IF we did decide to do a Prod bike that was manufactured a considerable amount short on cc's from the class maximum that we could legally stroke and bore to allowed class size. I was porting a customers roadrace engine and the engineering in it would definately allow the increase of bore and the crank design would allow a stroking and rod change within the cases without a problem. The oem transfer design in the cylinders would greatly benefit from a longer stroke and there is an over the counter piston that has a 5 mm higher pin height so that was how the discussion between my son and myself started, then he said it would be illegal and I said we would be allowed, I read the rules and so did he and we still disagreed thus the question on the board. The engine I was porting at the time is 102cc short of class size so the potential for improvement is substantial.
John