So it was in a garage today having the mufflers replaced and apparently the air filter set on fire and the guy had to pour water over it to put it out..

Is this possible if so how do I stop it?

 

It's definitely possible as it's happened to me too! It happens when you get a back fire through the carbs. More often than not, I'd say it is ignition timing related, but I'd wait for the more experienced guys to chime in.

 

YEP.

Wakes up even the dumbest mechanic real quick.

Ya want to see a V12 light em both up, that is scary.

On the SU engines, it is one of 2 things.

1) The timing is too far advanced.

2) The carbies are set tooooooo lean. VERY common.

The filters rarely ignite that much, usually smolder a tad, but if they are oily mist soaked, or older in age, then Guy Fawkes is going to pay a visit.

I would be resetting the mixtures, richen them a 1/4 turn wil do wonders, balancing the 2 carbies spot on, and check the timing very carefully.

If all that proves fruitless, then lift the inlet camcover, and ensure the inlet camshaft is dialed in correctly, as it could be a few teeth advanced on the micro adjuster, and that could, at a pinch, cause a back fire flame, but that would be a very long way down on any list I had to compile.

 

Standard procedure with a carb or filter fire is to crank the engine to suck the flame inside and prevent it's spread.

 

That's right!

Sometimes, though, when firing up cranky engines, I've run out of battery before getting the carb fire fully sucked in, bringing on some tense moments

Cheers
DD

 

Been there. Cardio exercise!!!


Good reason to have a charged fire extinguisher nearby!!!


Carl

 

"Tense moments", Doug, that is pure classic.

Other phrases do spring to mind before that one fpr me.