piston questions

[lee31]

I was thinking of boring out my 05 450 to a 470 with 11.5.1 comp. But I was told i need to replate the cylinderI dont really want toi spend an extra 200.00more. So i am thinking of getting a stock bore 13.1 or 13.5.1 My question is if I go 13.5 do I have to get difrrent vavle springs? I am thinking of leaving it stock bore with a 03 crf cam or stage 2 hot cam and port the head. If I go 13.5.1 compression with the cam and head porting how close power wise would that be to the 470 with 11.5.1 thanks

[lee31]

anyone with any knowledge please respond

[pro-rider46]

sorry i dont know much about 470s but a hi comp piston will help a LOT, and you should be okay with stocks valve train and a new cam. but you will have to run race gas (105+ octane) with a comp ratio above 12.75:1. check out www.rockenhorseweb.com and click on trx how to's and see the hi comp install.

[New450r]

I took mine to a 480 and went with a 12.5 and a st2hc went with bigger intake valves and I thought the extra money for the overbore was worth it but if you dont go with a 12.5 piston you can still run 93 pump but at least get it ported.

[chad502ex]

before you bore you may want to go with an exhaust, higher compression piston, a camshaft, porting, and all, if you can... valve springs are required when you go with an aggressive camshaft.

as for porting: I'm almost positive the feebleminded jokers from afar that has been flooding the ATVRIDERS gate lately with VENOM crap will be here tooting their gazooo before long. These guys all have dynos with power curves that are port hogged biased for peak hp with torque curves that simply sucks below 8000 rpm! If you wanting porting, simply find a porter that can validate the flow curve on a flowbench and not guess like venom has always been doing with his porting...