Yamaha beartracker 250 Quad problem

[Lukequinn]

I have a Yamaha beartracker 250 that I can’t seem to get running right

i am after replacing the spark plug, carburettor, and the carb boot to the engine when she starts she revs up like mad  even when the mixture screw on the carb is fully in when running she pops and stalls and won’t rev up 

has anybody have any idea what could be wrong with it thanks

[Gwbarm]

Sometimes when you put on a new carb the throttle cable might need adjusting, check to make sure the throttle plate is closing all the way. The mixture screw should be about 2 turns out. You might want to check your valve clearances to make sure they are correct.

[Mech]

It sounds like there might be several problems. If you wind the idle speed screw right out, and make sure there is play in the throttle cable so the butterfly is closed, then it shouldn't rev. Get it to run slow first, then find out why it's backfiring. If it won't slow down even with the butterfly closed off check the choke is right in and that there aren't air leaks around that new rubber inlet manifold. Some manifolds have a gasket or an O ring between the manifold and the head. It's been known to happen that the O ring gets dropped out during installation.

There are two types of backfire, one out the carb, and one in the exhaust.

 

[vlxerdon]

Just went through this on my bear tracker. It was just what GW said, throttle cable. Easy to replace.