flames out of the carbs?

[dtkid]

I have been refurbing an 83' GS1100G for a buddy of mine. I re-built carbs and some other necessary stuff. This morning I put the carbs on for the first time and it started right up (it had not been started in over 9 years), however, intermittenly the carbs would back-fire and flames could be seen through the pods I installed. I know I saw a thread on this matter a while back on this same issue. Can someone tell me what this back-firing into the carbs is an indication of. I was'nt surprised that I happened but I did'nt let it continue to run and "settle-down" because I wanted to see what you gurus' had to say about it.

The bike idles well and there is no dead-spot in the throttle which I think tells me that my choice of main jets, needle jets and pilots are ok. I know I turned the fuel-screws out about 3 turns. Also, I put foam-pods on the carbs (not K&N) so I think they are more constrictive than K&Ns'.

Any input is much appreciated: David

[pasteurized]

I'd be really interested to find out too. I had the same problem with my GS750 about a year ago. Except, I didn't realize it was spitting flames out the air cleaner until I took the original airbox off and realized it melted the rubber velocity stacks! I now run pods on it but I would be really interested as to why flames were shooting out the air filter.

[Hotblack]

I'd say combustion is getting back through your intake valves, either through improper timing or burned or worn valves. Sounds like you should first set your timing, and a compression check wouldn't hurt either. You do have a shop manual I hope.

[SqDancerLynn1]

CHeck the valve adjustment too!!!!

[duaneage]

Air and fuel will flow either way through a carb. This is obviously quite dangerous. Test it out side and make sure there are no fuel leaks.

You might have a valve that is hanging up due to crud on the valve stem. The cam lobe rotates off the valve, it is up to the spring to close it. Valves also rotate while the engine is running. A bent valve will intermittantly hold open as it rotates. This can be real tough to troubleshoot.

If the engine backfires several times in a row cut the engine and do a compression test immediately. you might find it hung open at that time.

[first timer]

it may also be the mix of the carbs, either to lean or to rich. i can't rember right now, maybe someone can back me up. i'm feeling it is to rich if it back fires out of carbs?

-ryan

[duaneage]

backfire from the carbs is caused (usually) by incorrect ignition or valve timing, stuck open valves, incorrect valve adjustments.

[rgierer]

I always feel abit foolish when i go down a road like this But, The only time I had fire shooting out of my pipes (I know they are not carbs) was when I had a bad stator and the electric for the engine was all ascew.

[focus frenzy]

having set for 9 years, there is a very good chance it is valves trying to stick open.