Box Stock

Stock Predator Backfire

K

Kman1771

Member
I have a stock predator that I race. This past Saturday it started backfiring when letting off the gas. Now when I rev it up it’s backfiring. What could cause this ?
 
if its all stock, go up two jet sizes. some times to small of jet will back fire... i don't know why, maybe someone will chime in. also check the gap between the flywheel and ignition. maybe a hotter plug.
 
I went up to jet sizes. Didn’t seem to help. Backfired all night Saturday. Yesterday I changed the exhaust gasket. Still backfiring. So I put a different exhaust on it and it still backfired. Valve lash ?
 
What plug? Change it if you haven't already. Check the timing! Do a leak down test. How fresh is the fuel?

It doesn't sound like a backfire, Could it just be a misfire? Where on the lap are you hearing this noise?
 
Out of the exhaust. It started out backfiring when letting off. Now it seams to do it more often. I changed the plug and it didn’t help.
 
It is bone stock. Has maybe 8 races on the motor. I’m running a 3910x plug with a 030 main jet. Fuel pump is pulsed of the valve cover. The engine still seems to be running strong.
 
Checked the float level in the carburetor. Sounds like you just getting too much fuel. Do you know the jetting In the carburetor?
 
Anything with a hotter heat range than a 3910x really. It's probably backfiring because it's not burning all the fuel your putting into it and it's getting hot and going off in the exhaust. Are the plugs coming out black?
 
Have you tightened the muffler/header? Start it and let it warm up, and then tighten the bolts. I have to check mine all of the time or it will start poppin
 
BrendanFitz#73 said:
Yeah switch to a hotter plug your getting an incomplete burn and just soaking the exhaust tract causing your backfire.
Click to expand...
Along with that when does it back fire ?.
If when you let off the gas to turn or make a sudden move . That closes the butterfly which causes a rich fuel mixture ,
Then you step on the gas and introduce a nice fresh charge into the chamber .
 
You must log in or register to reply here.
Back
Top