well u might wanna think about those....

 

when you put the HMF on,,,did you use the copper crush rings

 

If its poping your too rich and you need to turn the screw in 1/4 at a time. I had the same problem with my 450 until I turned the srew in a 1/4 turn. No more dam poping.

 

This is from the mikuni carb website.





4: Backfires in Exhaust

Note:

It is normal for many high performance exhaust systems to moderately backfire or pop when the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm.

The popping is a result of the air/fuel mixture becoming very lean when the throttle is closed and the engine is rotating well above idle speed. It is also necessary that the exhaust system have rather open mufflers.

Why This (normally) Happens:

1) When the throttle valve is in the idle position, fuel does not flow out of the main system (needle, needle jet, main jet). Fuel is only delivered to the engine by the pilot (idle) system.
2) The combined effect of the closed throttle and elevated engine rpm is to create a fairly strong vacuum in the intake manifold. This vacuum, in turn, causes a high air flow rate through the small gap formed by the throttle valve and carburetor throat.
3) Under these conditions the pilot (idle) system cannot deliver enough fuel to create a normal, combustible air/fuel ratio. The mixture becomes too lean to burn reliably in the combustion chamber. It gets sent into the exhaust system unburned and collects there.
4) When the odd firing of the lean mixture does occur, it is sent, still burning, into the exhaust system where it sometimes ignites the raw mixture that has collected ---- the exhaust then pops or backfires.

Other possible causes:

Air Leaks:

Any source of fresh air into the exhaust system can create or worsen the conditions that bring about exhaust backfiring. The most common entry point is the junction of the header pipes and mufflers. Even a small air leak can dramatically increase the intensity or likelihood of exhaust system backfiring.

A high temperature silicone sealant, as can be found in many auto parts stores, may be used to seal the pipe/muffler junction.

Lean Carburetion:

While exhaust system popping may be considered normal, it is certainly made worse by an overly lean idle circuit.

Be sure that your carburetor's pilot jet is the correct size and that the idle air mixture screw is correctly adjusted before looking for other causes of popping. The procedure for adjusting the pilot circuit is covered in the Tuning Manual.

Ignition:

If exhaust system popping is very loud, irregular and accompanied by loss of power, then you should suspect that the ignition system is not performing as it should. If, for some reason, the ignition sometimes fires at the wrong time, then exhaust popping can become very energetic (loud). Look for failing high tension leads (plug wires), failing ignition coil(s) and especially switches or connectors as possible causes.

 

more times than not,,,its caused by a lean condition

hondabuster hit the bullseye with that post

 

yea he did [img]i/expressions/face-icon-small-smile.gif[/img] ty man..

 

Thank yall very much I turned it in today and it only does it every so often im going to keep slowly adjusting after each ride. The spark plug has a nice brownish color so im in the ball park I figure. And once again thank you all I hope i can help yall oneday [img]i/expressions/face-icon-small-smile.gif[/img] . GOOD RIDEING TO YOU ALL. And by the way its not my raptor its my dads bayou 300 man that thing about drove me crazy sunday listening to it pop going down the hills

 

you mean out,,,,,,right

turn screw out to richen the idle circuit

 

YEA i meant out whoops!!!!!!!! I turned it probally 3 and a half turn before i got it

 

One more time TURN THE SCREW OUT TO GET RID OF THE POPING. If you go ut more than 3 turns, you will need a bigger pilot jet.