+1mm Pistons Superstock Legal?

[ekraft84]

Hey Guys,

Quick question - what's the reason behind +1 pistons being Superstock/Supersport legal?

Just curious.

Thanks.

[Protein Filled]

I believe they are legal as long as they keep the stock compression ratio.

[grasshopper]

My personal view at the reason why is because if the motor blew up or got damaged sometimes a hone on the cylinders isn't enough to clean it up. Then you'd have to bore it a little. I mean come on... How much power will 1mm give you if everything else is left stock?

[ekraft84]

That's debateable, but anyone serious about racing would be putting a +1 in as soon as they got the bike.

I'm still surprised this is legal ..

[lbk]

I ran into that with my SV, basically it sat outside so long that the only way to salvage the cylinders was to go +1mm. Honestly I don't think going +1mm overbore in and of itself really offers that much more than some of the other mods that are allowed in the rulebook. Of course then again 1mm overbore is cool, yet a K&N air filter will get you dq'd. LOL

[Woofentino Pugrossi]

This is right from the rulebook. +1 over is allowed in SS as long as compression ratio is the same.

D. Original equipment air box must remain as produced. Air filters must be used but
may be Aftermarket units. Aftermarket air filters are restricted to units available
via normal commercial channels and designed for that specific model machine.
Aftermarket air filter units that replace part of the OEM. airbox are required to
maintain the original size and number of air inlet openings as the stock unit.
E. Engine modifications include the following:
(1.) Pistons which are no larger than 1mm over stock size may be used but must
be same compression ratio as the OEM pistons.

Dave I dont know why a K&N gets you DQ'ed if its just an OEM replacement unless you had to modify the airbox to get it to fit.

[EX_#76]

I ran into that with my SV, basically it sat outside so long that the only way to salvage the cylinders was to go +1mm. Honestly I don't think going +1mm overbore in and of itself really offers that much more than some of the other mods that are allowed in the rulebook. Of course then again 1mm overbore is cool, yet a K&N air filter will get you dq'd. LOL

A K&N air filter is leagal as long as it has the same size and number of openings as the OEM air cleaner.

[Eric Kelcher]

This is right from the rulebook. +1 over is allowed in SS as long as compression ratio is the same.

D. Original equipment air box must remain as produced. Air filters must be used but
may be Aftermarket units. Aftermarket air filters are restricted to units available
via normal commercial channels and designed for that specific model machine.
Aftermarket air filter units that replace part of the OEM. airbox are required to
maintain the original size and number of air inlet openings as the stock unit.
E. Engine modifications include the following:
(1.) Pistons which are no larger than 1mm over stock size may be used but must
be same compression ratio as the OEM pistons.

Dave I dont know why a K&N gets you DQ'ed if its just an OEM replacement unless you had to modify the airbox to get it to fit.

K&N does not make an OEM replacement for the 1st generation SV and therein lies the problem with it. BMC makes two versions one that is legal and one that is airbox mod similar to the K&N.

As to the 1mm overbore it is a maintaince issue to allow machines to be revamped rather than replaced, similar to decking a head to insure proper seal due to blown head gasket/overheat/etc of a motor.

Modifying a good part for a performance advantage was not the motivation behind the rule.

[MELK-MAN]

a worn motor getting a 1mm overbore is not always the best way to freshen a motor. The engineers have things worked out very well for a supersport motor. It is potentially a better idea to replace the cases. You will spend a good deal of money having old cases bored, and they will still be old cases. Then finding high quality aftermarket pistons is a job.. OEM new you cant really go wrong with. Just finished building a motor for my 05r6, went with new cases, new pistons, bearings, rods, valves.. all stock. Best motor i have ever had.

[lbk]

The K&N did in fact have a slightly larger opening than the stock air filter, after I found out it was no big deal just went back to stock. It's just amusing to me that a 1mm larger opening on the air filter dq's you yet a 1mm larger opening on the bore doesn't. Again I understand the rule for allowing overbore like I said if it weren't allowed I would've been up a creek and simply because I bought a used bike that needed it, I just don't think the larger air box makes a big difference either. I've been dq'd by that rule, and I've gained a position because of that rule, and even when I gained the position one of them resulting in a win, I still found it funny and felt sorry for the guy that didn't know aobut it. :D

[ekraft84]

K&N does not make an OEM replacement for the 1st generation SV and therein lies the problem with it. BMC makes two versions one that is legal and one that is airbox mod similar to the K&N.

As to the 1mm overbore it is a maintaince issue to allow machines to be revamped rather than replaced, similar to decking a head to insure proper seal due to blown head gasket/overheat/etc of a motor.

Modifying a good part for a performance advantage was not the motivation behind the rule.

But if I had a brand new Supersport build 600, I could go +1 and still get a performance advantage correct?

I see the point of this being a "maintenance item", but I've rarely heard people complaining, "well if I could have gone +1, I would have been a lot better off."  That doesn't seem to happen much.

It just strikes me as odd that the AMA doesn't allow that, WERA doesn't allow that (I can't speak for AFM, CMRA, etc.), but CCS does.  The intent of the rule may have been all good, but the performance advantage is there regardless whether it's needed for the intended purpose or not (as minimal as it may or may not be).

[Super Dave]

1mm over bore?  Was allowed for some time as a reasonable opportunity to rebuild a motor.  With iron bores, it was easy.  With the new aluminum bores with chrome bores...I think it's more of a project and an expense to execute, an over bore.

I'm with Greg.  The bore and stroke, the combustion chamber size and shape, the weights of all the parts were designed to pretty specific parameters.  Stuff's pretty darn good, really.  I'd leave it alone.