Suzuki GS 750 - Backfire

[Hariii]

Good morning everyone, 

i have a problem with my GS 750 lately and could really need some help or input. But first excuse my english vocabulary, it's not my main language. 

As soon as the engine gets warm, it backfires and i have no idea why. I use K&N Pods, new coils, new plugs, a Dynatek S, new intake manifolds etc. Got the right jets for the carbs on a test bench and it runs really well...Except for the backfire and the drop in rpm in neutral position. Here are some vids that hopefully help you to understand my issue...

 

[FJD]

Too lean, mixture screws or pilot jet richer

 

Thats not backfire btw, its farting in the exhaust

Edited August 9, 2022 by FJD

[Hariii]

Already tried that and it is definitely not too lean...

[Gixer1460]

1 hour ago, Hariii said:

Already tried that and it is definitely not too lean...

How do you know that? When you said 'backfire', I was imagining a bang from the exhaust! That 'tick' is deffo carb related and usually symptomatic of a lean condition. That is so small meaning jetting is nearly right, worse cases are proper bangs and can blow the filters off! Try taking the filters off (they should be oiled btw if K&N - which would richen mixture a tiny bit) and see if the problem is worse? Or wrap masking tape around filter, blocking half of the filter area and try that - the airflow reduction should increase the mixture. All solved with a jet change ie. up on the idle jet! Otherwise book a dyno session that has a AFR meter and do it properly rather than guesswork.

[Hariii]

Thanks for the tipps say what now!?. Turned out that the carbs weren't synced at all and after doing that, the tick is finally gone. Now the bike runs really damn nice