motor building questions

[the yazer]

I'm looking to give the 450r some more power with out going to a bigger bore (need to keep it legal for mx). i was thinking a high compression piston, but i still want to be able to run pump gas. I do some trail rides where you HAVE to stop at the gas station or you will not make it home !

so i guess i need to know. how high compression I can go and still run pump gas, what cam will work best with that. and what cdi i should go with?

I already have my mind set on a hmf full exhaust

I ride 85% mx and the rest trails

thanks for the help ahead of time

Justin

[jeepeater347]

What cam are you running? If your using the HRC or Hot Cam Stage 2 12:1 or 12.5:1 would be fine. If not I wouldnt go past 11.5:1

[the yazer]

I was thinking about running a stage 2 hotcams

[RedRacer44]

I tried the 11.5:1 JE piston and was dis-appointed, no power gains at all. I was trying to keep from running race gas but I bit the bullet and got the JE 13:1 piston. My quad rips now, runs great!

I have the StageII HotCam and love it, really pulls hard from mid-range to top end w/out any loss on the bottom. Great performance and great price!!

If you dont want to go to hi-compression, stick with stock piston and just put in the HRC or StageII HotCam. Its the most cost effective upgrade in my opinion.

[Kilabanshee]

The je 13.1 piston along with the thermal coating which c&d racing does should run fairly safely on 93 octane. If you have a sunoco dealer they sell 94 which would help alittle bit and you can also mix alittle bit of race gas with 93 to get it to the octane level your looking for.

[29FTEX]

A 12.5:1 or 13:1 will allow you to run regular gas, as long as you use a cam with enough overlap, like the HC stage 2 or HRC. If you go this route, make sure that the gas is fresh as well.

[RedRacer44]

As far as I know, you cant run pump gas with the 13:1 pistons unless you get the thermal coating done to the cylinder.

I have the JE 13:1 w/ StageII HotCam and from what I know, you have to run race gas. The pump gas wont detonate (cant spell) right without the thermal coating. I know on my buddies 425EX, we put a 13.5:1 piston in it....he tried running 93 octane and it caused it to blow head-gaskets. The same should happen with the 450 hi-comp pistons

I ran a 50/50 mix of 93/111 octane at the dunes and my bike ran like crap compared to the straight 111 octane. Just going off what I know.....

Maybe I dont know anything ??
:huh

[Kilabanshee]

I'm almost sure that with the 13.1 piston and the hrc cam without the thermal coating that you are able to run 93 octane but the gas has to be fresh. c&d doesn't thermal coat your sleeve they just aply it to the top and sides of the piston. Use about a 1/3 c12 and 93 mix when I'm just doing a normal riding. I put 1 gallon of the c-12 right into my gas tank and top it off with 93 and just shake the quad back and forth for a few seconds and it seems to run great. When I'm Racing or doing hard riding I usually run a 3/4 race to pump gas mix.