Shooting exhaust pipe.

[Ib-Denmark]

Hello,
Now I really dont know what to do!
After reassembling my G 80 S 1957 this "Spring" I have got a problem.
Each time I close the throttle the engine fires in the exhaust pipe. The bike has never behaved this way before!
Everything else is function fine: Starting, driving idling a.s.o. Its just that damned shooting.
This winter I have made the following changes
( besides having the engine dismantled):
1.: The carburettor has got a nice fitting sleeve for the throttle.
2.: New contact breaker.
3.: New auto advance unit
Please help me.
Ib

[Rohan B.]

Popping and banging in the exhaust pipe on the over-run, also called backfiring, is usually caused by an air leak into the exhaust pipe or where the muffler joins the exhaust pipe - look for any signs of blowing or black soot escaping.

It may also be a poorly fitting carburettor, allowing air to leak in. Or possibly a worn inlet valve guide, allowing air in.

Try richening the idle mixture a little, if that doesn't help I'd be having a close look at how good the exhaust pipe seals onto the exhaust port - muffler putty or a high temp silicone can often help here.

hopethishelps,
Rohan.

[RogerNorman]

If you have a Monobloc its also worth checking the pilot airway in the intake of the carb. Its a very small hole (as you would expect) and needs to be carefully cleared - air line is probably safest. My Green Laner used to suffer from this problem which eventually became a pain on trails. Everytime you shut down any cows, sheep or worse, horses in the area used to bolt!

[Ib-Denmark]

Everything is easy, - when you just know what to look for!
It was nothing but a wrong idling mixture.
What an effect!
Now I am happy again and ready for the International in Norway.
Perhaps I see some of you there.
Thank You
Ib Vestergaard
Denmark