help please bf 750 backfiring

[chine]

could someone please help my engine keeps backfiring would could i do

[God Of Thunder]

well what'd ya do to cause it to start backfiring? what year?

[jawsfx4]

hey, mine was doing the same took a long time but finally found that the exhaust pipes where they bolt on to the motor were cracked.the crack started right at the motor and went back about six inches they were both in very hard to see places. welded them up and its good to go,just make sure if you are not too good with a welder dont try to do it yourself the pipes are surprisingly very thin.

[Kenny4]

How did you find those leaks in the pipes---I have sprayed Engine Start all around my pipes especially at the headers to no avail---It's supposed to increase the idle if there is a leak when the ES goes over it---I've tried every combo of jetting, A/F mix etc---Still

Kenny

[DaBrute]

Quote: Originally Posted by Kenny4

How did you find those leaks in the pipes---I have sprayed Engine Start all around my pipes especially at the headers to no avail---It's supposed to increase the idle if there is a leak when the ES goes over it---I've tried every combo of jetting, A/F mix etc---Still

Kenny

I think one would use engine starting fluid around the intake to check for leaks if your expecting to hear the idle raise. Spraying it around the exhaust i think would do nothing, as this area is post combustion. Take a welders wire brush and buff your headers and pipes clean, that will show cracks in dark lines.Also have you checked your valves for gap? Sometimes they get a little tight and will cause backfire issues exspecially on hard decel of the throttle under load ie:downhill.

[Kenny4]

Noop---Been holding off on the valve adjusting---Didn't want to go there if I didn't have to----Must be something you can spray around the header gaskets that will show if there's a leak

Kenny

[jawsfx4]

dabrute is right,clean them up real good should see them or maybe the leak is further down where the pipe goes in the muffler,you can also heat the pipe red if there is a crack it will expand.i found it when i was doing the valves had the batt out, you could just see something on yhe side took it off sure enough it was cracked took the other off and she was done too.

[chine]

so if your pipes are cracked that will cause backfiring.what causes the engine to take a long time to start?

[DaBrute]

Quote: Originally Posted by Kenny4

Noop---Been holding off on the valve adjusting---Didn't want to go there if I didn't have to----Must be something you can spray around the header gaskets that will show if there's a leak

Kenny

You can spray Magnaflux on the pipes and it will show you the cracks if any,but your pipes will have to be cleaned first.

[nfox]

IF it cranks for a while before it starts if you are carbed u might have a needle and seat leaking fuel into the cylinder.