suzuki gs1000st running rough - snap crackle and pop

[met]

hi folks....me again.

same bike wes cooley 1000st - new problem.

the bike was sent away 3 months ago, to get carbies cleaned and fitted with full new kit.
also had service and tune done together with carb balance.

engine was done about 1000kms ago.

came back to me and it started 1st time every time
and rode like an absolute dream for about 200 kms.

then on the last ride after about 6kms of riding it started to pop and backfire just out of the blue that also affected the performance of the bike.

7 km later and it brought me home ok, lame as it was.
plugs are ok...i did a night check to see if there's short anywhere, all ok there.

now, it still starts 1st time every time but it has that backfiring noise and offcourse i am reluctant to ride it more than a block away....

im thinking carbs...?
but then ...........the carbs were done.

any ideas?

[Nessism]

Is there any rust in the tank? And have you ever changed the petcock?

[met]

ah yes - i forgot....tank is free of rust and had a tank liner put in about 9 months ago.
petcock is new, but has a slight leak out of the one mounting bolts, to which i will fix.
but.......apart from the petcock filter, i don't have a secondary filter on the fuel line.

[Big T]

Drain a carb or 2 into a container and see if there's any sediment

[salty_monk]

You could also look for an air leak, check the ignitor & check the connections at the coils (check for spark). I had a Dyna coil go bad that gave similar symptoms.

[Boriqua]

Crazy thought while you are checking stuff. I was suffering some popping but it wasnt really loud enough to hear but I could feel it through the pegs. I remembered when I was a kid and I took the baffles out that I experienced the same thing so since I am not the original owner of this I thought .. let me go over the exhaust from front to back. Turns out my right muffler clamp screw was stripped out and wasnt providing a good seal.

Off to home depot for a screw .. tightened it up well .. and it was gone. Just thought I might throw that out there.

[Kiwi Canuck]

ah yes - i forgot....tank is free of rust and had a tank liner put in about 9 months ago.
petcock is new, but has a slight leak out of the one mounting bolts, to which i will fix.
but.......apart from the petcock filter, i don't have a secondary filter on the fuel line.

Check your coils both primary and secondary for the correct resistance, the readings are in the supplemental manual page 9..

http://zeus.mtsac.edu/~cliff/storage/gs/GS1000S_supplement.pdf

I had similar symptoms with the GS650 and had a flaky resistor in one of the plug caps, bike started OK but misfired once under way.

Did you install the correct washers on the fuel cock, rubberized washers, they are item # 4 in the diagram, without them the fuel cock will leak.
https://www.partsoutlaw.com/oemparts...e9c2/fuel-cock

BTW in line fuel filters can cause issues with the CV carbs, there should be a good filter in the tank that should do the job if you replaced the fuel cock recently.

Good luck.

David.