85 200x 12:1 question

[3wheelBandit]

i gotta freshen the top end of my 200 and was thinking of going to 12:1 wiseco but wanted to ask what else needs to be done to compliment this. do i gotta run bigger jets, carb, exhaust, cam? or can i plug and play? i know i gotta use higher octane too right? thanx

[Thorpe]

i gotta freshen the top end of my 200 and was thinking of going to 12:1 wiseco but wanted to ask what else needs to be done to compliment this. do i gotta run bigger jets, carb, exhaust, cam? i know i gotta use higher octane too right? thanx

Yep... Gonna need all these.... Not just a plug and play anymore...

[Vealmonkey]

Your better off just using a stock compression piston. At 12:1, you will need to run racing gas. More hassle then it's worth.

[TheRealFatShady]

Could you use an XR200 cam, XR200 carb, then aftermarket exhaust?

I have a spare XR200 bottom end I plan on using on my 200m with 200x kicker gears, 12:1 or 13:1 if I can find one, and use it for a speed set up.

[RIDE-RED 250r]

Your better off just using a stock compression piston. At 12:1, you will need to run racing gas. More hassle then it's worth.

agreed....with a 12:1 piston, you are definately in race gas territory

[joshco84]

agreed....with a 12:1 piston, you are definately in race gas territory

and not even that it is so expensive, its hard to find a lot of times, and never available (IE the speed shop isnt open) when needed.

[WilliamJ]

Here in the UK we can get 99 RON at the pump - not sure what the highest US octane is but I have a feeling its measured slightly differently - a combinatation of MON and RON maybe?
Anyway, 12:1 on 99 RON can be okay but it does depend on your camshaft. If you have a wild cam then you can, in fact you should, run a higher CR. I have run a race engine with 12:1 on 97 RON but it had a longish period cam (295 degrees) with a big inlet/exhaust overlap. The size of the overlap is important as the longer the exhaust valve stays open while piston is travelling up the bore, the lower the dynamic CR is. Do you know what the timing numbers are on the stock cam?

If you can't get the right fuel though you should keep the CR down.

[mullet_boy]

I run a 12:1 in my 200x. Can't really say what it will do on a mostly stock set up, but with just a pipe filter and carb on mine it was noticeable. I just jetted for e85 and have ran that since. Readily available in my area, high octane, and its alcohol to boot. If you plan on staying stock, throw in a wiseco 10.25:1 and call it a day. 12:1 tends to do horrible things to kicker gears as well as requiring higher octane fuel. If you want the hassle, it is worth more power. If not stay closer to stock cr.