backfiring?  By  bobby17772 (Read 601 times)

Backfiring is easy to distinguish, it sounds like a gun went off or firecracker POW POW, then you have POP sounds then you have what I call BURP or BRAT sounds each tells you what the problem may be.
So you have to be sure what it sounds like because each points to different problems.

Backfiring is caused by running really LEAN or out of TIME.
Now the Backfiring usually caused by a really bad air leak, the usual spots to check is the FLANGE that connects to the motor that is welded to the pipe. It could be loose or one or both of the nuts vibrated off or even a stud in the head came out and blew the gasket partially out.
Or the leak may be around the carb, by the intake manifold, Air Filter tubing air box etc..

Since you put in a new HEAD I would first check your timing.


If it is a POPPING sound on throttle it is way to RICH and a smaller main jet is needed.

If it just POPs coming off throttle at low rpms then just need to richen the Fuel Ratio Mixture a little more or raise the IDLE a little(sometimes that is enough).

If it BURPS or BRATS sound on throttle it is just a little LEAN and richening the Fuel Ratio Mixture will take care of that.
Alleyoop

Yep sure sounds like it is to RICH, go down on the MAIN JET.

Getting the right jets is a TRIAL and ERROR situation all motors are different have more compression than others and different mufflers and air filters change the jetting requirements.

When someone says mine runs with this and that those same pieces on his might not work on your motor.

But it is always better to be on the rich side when running a motor then you can dial it in by going down.
Alleyoop