I just bought a 1989 moto4 worrior 350 the guy I bought it from had a litype exhaust that broke off and rode it like that for awhile so I bought it off of him rode it then I was getting low on gas got some from a friend before I could get home I notice it started backfiring and I geared it down and got into it it bogged and cut off now I can't get it started all it does is pop and backfire once in awhile it'll blow constant fire out the exhaust im hopping it aint a burnt valve

 

check compression it's more than probably something simple change the plug look at the old one it will tell you a story if you look right

 

Ya I already changed the spark plug same results like it's wanting to start but it ain't

 

You have a fuel issue most probably if there is no compression it may be bigger issue but pull your plug out check compression.Check for spark as well,

If you have compr. and spark the problem is FUEl

 

It has compression and spark everyone I talked to says it's a burnt valve

 

Have you checked valve clearance? May be all it is. If that doesn't help then you can do a leak down test and it will show you real quick if the valves are leaking,plus you can hear air hiss from either the carb or exhaust.If it's leaking more than 25% then it's good enough reason to tear the head off and check things out.

 

I think it has something to do with the heads

 

How much compression does it have? Burnt valves usually cause low compression.

Have you checked for fuel flow? When you get "low on gas" is usually when all the trash gets sucked in the carb. That's really what this sounds like.

I'm not sure i understood...but if you said the exhaust was real short, then i probably will blow fire out of it.

 

Oooo ya lots of fire haha

 

So one kik me GoBugs956 so I can send pics of the bike and stuff