back fire through carbs

[thebilby]

My engine starts and idles fine, a bit noisier than normal. when you put it under load it sounds like it is back firing through the carbs. any ideas?

[waltraud]

Sounds like lean condition, u changed anything recently? Might be worth seeing if there's any blockage in carb jets, any othe symptoms?

[BOXY]

If it's an Aircooled, twin carb check the nuts holding the carbs to the manifolds haven't come loose. If they have it could be pulling in air weakening the mixture? What do you mean when you say it's noisier? Is the exhaust louder or the induction side louder?

[thebilby]

I disconnected all of the plug leads from the right hand bank and it made no difference!! compression test showed all cylinders at 115 psi.

really stumped.

[mark]

ive had this on a couple of Aircooled engines sounds more like a sneeze than a back fire, you need to squirt some wd40/carb cleaner at the the inlet manifold gaskits carb bottom and heads. you should hear the engine note change, replace gaskits and bob should be your uncle

mark

[john1]

Just a thought.

My hydraulic tappit was not opening my exhaust valve fully, this caused a blow back up the carb.
I couldn't get above 30mph and it was chapping on that side.

Put oil in and took it for a driver and it was ok after that.

Not sure your problem is the same but thought i would share anyway.

john