engine mods?

[mudrunner35]

what's the most you can do to the engine while staying on pump gas? i don't want to do race gas

[Cool Guy07400EX]

You can do as much as you want, just keep it at 11:5.1 compression or lower.
Even with 11:1 comp. you sometimes have to run a 50/50 mix of pump and race gas.

[drew416ex]

It also has to do with the size cam you put it in. A motor with 12:1 compression can have less cylinder pressure than a motor with 11:1 compression and a small cam. But gennerally the rule of thumb is 11:1 and lower on pump gas.

[Wheelie]

My engine runs fine on pump gas with about 11.3:1 compression. I run 50/50 at the dunes though.

[mudrunner35]

i don't know a whole lot about engines, but if i put a 416 or a 440 kit in it i could still run off 91 or premium? someone's going to have to explain this compression thing to me:confused:

i say if you bore it stay at 10.5:1 or 10:1/ If you dont bore it you could still do 10.5:1 or 10:1, curtis sparks advanced timing key, exhaust, air filter lid removed if you want more power, stage 1 hotcam. theres a bunch of things to do.

[drew416ex]

Originally posted by mudrunner35
i don't know a whole lot about engines, but if i put a 416 or a 440 kit in it i could still run off 91 or premium? someone's going to have to explain this compression thing to me:confused:

Yes you can still run on 91 octane as long as you dont go over an 11:1 compression piston. When you buy a piston it should tell you what compression it is: 10:1, 11:1, 12:1 etc. The compression ratio is the ratio between the volume of air when the piston is at the bottom of its stroke to when its at the top of its stroke. Highter compression ratio means more cylinder pressure which if done right means more power.

[mudrunner35]

thanks guys :) if i bought a 400ex how much would it cost to keep up with a 450? because most of my friends ride 450's. would it be reliable or would i be farther ahead to buy a 450? i sat on both and i like the way the ex feels and i don't have to stretch my arms as far to reach the bars so the ex would be a better choice for me