Motor skiping and runs like crap

[Mud Goat]

I'm working on a friends honda 300 4-trax and I can't figure out wats rong. The motor idle's like it's on steriods(i.e like it's got a mean cam). it has a straight header, but i'm gonna put a muffler on it asap. when you rev it it cuts out and misses.
I put a new plug and air filter on it and it helped alot. it will idle now with the new parts. any help is appreciated.

[rooster300ex]

Probably needs the idle turned up & an exhaust. I had my 300ex without a muffler for awhile(other one broke) and i ran better. or it might of been cuz it was as loud as a dirt track car.

[2muchquad]

its probably real lean because theres not silencer,you better get one on there or you could ruin those exhaust valves,im sure its crazy loud but its losing power big time without it:rolleyes:

[bwamos]

Real twitchy/revvy at idle usually means you have an air leak somewhere. Either at the intake or exhaust side.

Your motor cuts out at high throttly because the atv is running way to lean without the muffler on there.

Replace the pipe. Replace the Exhaust crush gasket. Clean up the intake boot and check for leaks.

Then rejet the carbuerator for the new setup.

[wboy62417]

PUT EXHAUST ON IT that is bad on the vavles please do this b4 you ride it you will burn up your exhaust vavles if you dont

[Mud Goat]

Alright here is what it's doing now. We turned up the idle, and put a factory pipe on it and it still misses, then I felt something burning on my leg and I looked down and there was oil pouring out of the motor. It's got a cracked head:confused: :eek:
It will rev to about 1/4 throttle then it will pop and miss again.
is there anything I can do to it to make it rev, as my pal can't afford to have it rebuilt.

[fitethesystom]

Pretty much if there is a crack there is no other way but to replace it...

[ZeroLogic]

JB weld might work for a short term use but I would deffently buy a new head.

[fitethesystom]

JB WELD IS GOD.

[ZeroLogic]

It might crack from when it expands from getting hot and then shrinking when cold.:ermm:

[fitethesystom]

nah i wouldnt bother, i would just bite the bullet and replace it with a used one and have it off my mind....just me though