PDA

View Full Version : back fireing ex


badass300ex
04-19-2003, 09:57 AM
I have a 03 300ex. I have a full DG pipe,K&N< and its been rejetted all done by my dealer. Heres my problem It always pops and backfires when reaching high rpms. The dealer says when you add a perfomance pipe it will backfire. Peoplke are telling me it shouldnt. When I push it hard through all 5 gears and let off the gas it pops and backfires like crazy. Is it running to rich?Dealer cant do anything else for me.
TRX_Thumper
04-19-2003, 01:09 PM
bump the pilot jet up one size
canadian400ex
04-19-2003, 01:35 PM
My geuss is you have an air leak in your exhaust system somewhere. (probably where the pipe and silencer join together). Check it out.:)
phatswinn
04-19-2003, 03:04 PM
canadian400ex is right, mine did that before i got a little $12 gasket that goes inbetween the header and silencer from my dealer
White_Knuckles
04-19-2003, 06:09 PM
With high-flow exhaust systems 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 airflow rate through the small gap formed by the throttle valve and carburetor throat.
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.
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.
modracer5
04-19-2003, 11:37 PM
i just put a new pipe on friday and my bike was popping like crazy sat when i went to ride. found out that the copper crush rings that go between the header pipe and the motor had stuck to my old pipe when i took it out causing it to suck air. put in 2 new crush rings and it stopped.
250EXking
04-20-2003, 01:10 AM
it sounds like your running lean. you have to increase the jet a little bit. for a little more gas.
300exazzkikr
04-20-2003, 02:20 PM
Originally posted by 250EXking
it sounds like your running lean. you have to increase the jet a little bit. for a little more gas.

NO. definetly not. If anything your running rich bump the pilot up. But most likely the exhaust is sucking air somewhere, mine did it too until i found the little gap where it was suckin air.