Engine backfire's

[Millhouse]

Does anybody know what causes the engine to backfire, it only happens when going down a hill its fine otherwise.
is this normal?
im running a 1600cc with twin carbs, electronic ignition and a quiet pack exhaust.

 

[gvee]

I had this when slowing downhill; caused my a funky air-petrol mix.
I did this myself, but I only run a single carb so just toyed around till I got a better engine noise, not sure with twins; I guess you adjust the mixture screws on both together (assuming they're already balanced).
Well, I don't feel that was a very useful response, sorry :lol:

 

[matt-me]

look for any air leaks on the exhaust connections. My back fire was one of those

 

[ozziedog]

Does sound like an exhaust / air leak if it`s just on the downhill /overrun stuff. If it is causing your bus to backfire, then it should be a fairly obvious leak and easy ish to spot. Good luck with it,, and report back as to where exactly the exhaust was leaking

Ozziedog,,,,,,,,,,,I like a bit of banging every now and then ! :lol: 8) :lol:

 

[Millhouse]

Thanks for all the help. I'll have a look at the exhaust pipe over the weekend and let you know if i find any leaks or not.

 

[rev-al]

Look for an air leak at the the carb.
A backfire on the over-run could be an overly rich mixture - so un-burnt fuel getting out the exhaust valves & igniting next fire. ? (My Bonneville can do this due to either reason).
Good luck with it.