Backfires I have a 2006 suzuki s40. I just took it in and had new jets put in because you had to ride with the choke wide open and had a lot of backfire when slowing down using the transmission. Now it runs better but at times will still backfire. I was told a new muffler would do wonders because they built the bike for emissions and it has trouble breathing.?? or something like that. What do you think?

Yes if it only runs with Choke, it has jets that are partially obstructed. Video should help.

https://www.google.com/search?q=2006+suzuki+s83+boulevard+clean+carburetor

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If you are lucky, you might just need new fuel filter and the fuel bowl cleaned out, and maybe new air filter. If not so lucky you need carburetor rebuilt. Backfire is usaully caused by engine running too lean ( too much air for the amount of fuel present). Fuel bowls get gunk in them and the fuel needles and fuel jets get varnished up. The accelerator pump gets worn out gaskets and/or bellows and doesn't give the right amount of fuel mist when you accelerate.

Full Choke is indicative of a motor starved for fuel

at wide open throttle the jets in the carb might be dirty not sending enough fuel for the demand

hi, first thing to do is identify if all the exhausts are hot when the engine has been running for a minit or two, probably the backfireing you are hearing is at least one of the spark plugs has become contaminated with fuel and as a result the engine is not running properly on that cylinder, the backfire will be the exsess fuel igniteing as the plug becomes warm and then fires, it may also be that the fuel has become contaminated, causing a varnishing effect within the float chamber, thus blocking or restricting the fuel flow through the main jet, the machine would run on primary jet and of course the choke jet, but would fail to respond on throttle opening through the main jet, try drain old fuel from float bowls, hope this helps welcome to the motorcycling world, the more you learn about the machine you ride, the more you will enjoy rideing it, paul edwards

Its not common with YZ but is very common with not starting the bike for long time - you need to take out the pilot jet and replace it with new, You could clean them but why bother they about $5 each?
If I were you whilst you have the carbi off I would change all the jets to new ones especially as been sitting for a while (not essential but worth while as off already?)

running only with choke on and backfire are classic symptoms of blocked pilot jet or incorrect size pilot jet so chuck new one in and you should be good to go
The pilot jet is the jet closest to the engine when carbi was installed (it has perforated holes on the side)
good luck regards Jamie

Ride the bike 20 or so miles on open road. Stop and remove plug to inspect. 'Are they black or white ?


Black =rich white=lean

Sounds like the carb is frozen or the ignition timing is way out (check distributor and loosen the clamp, turn it slightly with the engine running until it idles and revs up nice) . Reset the ignition timing, if that does not cure it, a carb rebuild is on the cards.

Vote for me if this helps, thanks.

Not for sure but u might try to re jet the bike.i own a 98 suzuki bandit 600s and it also is really cold hearted. those bikes are unfortunately known for that problem.not that it was much help but u might try contacting Dales Holeshot Performance he specializes those types of bikes he also sells the jet kits.
i would also try to adjust the idle slightly higher hope this at least helps