GSX1100F running poorly

[Ivan V]

Hello all, my first post. After doing some reading on running problems I have come to a conclusion that my carbies are not preforming as they should. I have a 1989 Suzuki GSX1100F . The bike runs with bad spluttering and backfiring through the rev range. I removed the tank and air filter and set up a bottle of fuel to run it so I could see a little easier as to what the problem could be. While running carby no 2 is backfiring and feels like it is too rich. I have not run the bike all this year because of this problem and is giving me the wobblies.
I think the the needle and seat in the no 2 carby is faulty, can somebody please confirm this?
Ivan

[92xjunker]

Backfire-through the carb. Afterfire-through the exhaust. If it is a backfire, check your sparkplug/ wire sequence. (Left coil-plugs 1&4 right coil-plugs 2&3). Afterfire is a lean condition, most likely a carb cleaning is due.

[maniac1886]

You say 1989..... I say yup, clean the carbs.


It will run wayyyy better if you get them all the way clean. I fear, only fixing cylinder 2 is a band-aid and the other three would likely need some attention at some point. Might as well do it all at once so you dont have to keep taking them off.

You'll likely need float bowl gaskets at the very least. Probably float needles and some orings too.

[shpielers]

What is making you think #2 is the problem? Is that header temp cooler than the rest? Hotter? If it's running rich, it will be cooler. Could be rich because of a bad float valve o ring, the needle wearing after years of use, the emulsion tube being out of round, or varnish/debris keeping the float needle from completely sealing. If one header is hotter it is running lean. Likely due to an air leak. Find it, seal it, pat self on back.
Also, make sure all 4 air/fuel screws to 2.5 turns out.

[Ivan V]

Thanks gents for a quick reply.
Mr 92xjunker the spark wires are correct although not sure if I am getting possibly some crossfire through the leads.
Mr maniac1886 last year I had the carbies tuned, I believe the needle and seats were replaced and it ran quite well, basically it sat in the garage for 12 months without use.
Mr shpielers as I mentioned in my original post only carby no 2 is backfiring as I could see flame coming out of it, others seem ok.

[maniac1886]

Did you drain the carbs before letting it sit? Or treat the fuel with stabilizer?

[92xjunker]

Try running carb cleaner in the fuel. If that fails, you're going to have to reclean The carbs

[Kreylyn]

I know "carbs" is always the go to point, but... seriously... how would they cause backfire?

Something is causing a spark when the intake is open. That's what causes a backfire on these bikes. Carbs don't do that. What work has been done to the bike. Any work done in the engine at all? When was the last valve adjustment? Are all the valves closing fully?

I see the plug wire order has been addressed. So lets check the wires to the coils are correct, and not been switched. Run the bike in the dark with the tank off to check for any arcs across plug wires. If none of that is an issue, then I'd check the ICM for possible issues. Check the plugs on it, the wires coming out... make sure nothing been in there chewing on things to cause cross connections. Final and very last thing would be to temp swap the ICM with a known good one. Unfortunately there is no other way to economically test the ICM directly.

Krey

[92xjunker]

He never acknowledged if it was a backfire of afterfire. Assuming it was an afterfire, since Kats dont have a tendency to backfire. Carbs are a logical target if the bike sat for a year.

[Kreylyn]

He never acknowledged if it was a backfire of afterfire. Assuming it was an afterfire, since Kats dont have a tendency to backfire. Carbs are a logical target if the bike sat for a year.

I was going by this...

Mr shpielers as I mentioned in my original post only carby no 2 is backfiring as I could see flame coming out of it, others seem ok.

...As confirmation it was backfire.


Krey

[92xjunker]

Check I suspected a plug wire but, a valve issue could also be the problem.

[Ivan V]

Yesterday I replaced right hand coil and high tension leads and ran the engine. Nothing changed. This morning I took the carbies off and checked the needle and seats and the only possible problem I could see is one of the o rings on the needle housing was damaged, so I replaced them all. The seats and needle sealing areas are very good as they are new replaced last Christmas by the bike mechanic. I also checked the jet needles which had a little of brown gunk which was easy to remove with my finger nail.
Made sure that all needles are sealing by filling the bowls and blowing in.
All of this still made no difference, still occasional popping and backfire through the second carby. The bike has little more than 50 k on the odometer which makes me think that it is too early to have a valve problem, but anything is possible.
Happy new Year to all, Ivan

[92xjunker]

Popping threw the carb is a timing issue, valves are timing component. When you turn it over does it puff threw the carb? ........thinking.....it can't be a timing chain or the pulse generator, the problem would be on multiple cylinders. Could be a carb issue, flooding fuel remaining in the cylinder then igniting on the #3 compression stroke....not likely though. Valve tightinging up is possible and does happen. Could be a mix of both carb and valve issues..

[Ivan V]

On Monday I checked valve to rocker arm gaps and all was very good with in manual specs. To check the gaps I removed the spark plugs so I could turn the engine a little easier. When I installed the spark plugs back I swapped 1 with 2 and 3 with 4 so if my problem still exists it would show itself but at different positions.
When I started the engine my first thought was if my old man was still alive he would kick me up the rear for missing such an obvious mistake. Obviously I had overthought the problem not realizing that a plug could be such a problem.
Thanks gents for your inputs.
Gratefully Ivan