I have a 03 Suzuki Vinson 500, earlier this year it would fire up fine and idle/run fine up until the motor warmed up, then it would progressively get worse on idling, to the point it would shut off if I didn't have my thumb on the gas. Now it wont run at all on idle and spits and sputters while throttling all the while blowing white smoke. Took the carb and cleaned it, even though it had no varnish in it at all, changed spark plug. Still the same result. Please, any suggestions.

First suggestion, Should have bought a Honda.

Did you change out the fuel?

Yes changed the fuel wiped out tank with a towel. I also just about run non eth gas exclusively.

Hondas are nice. But this Suzuki has been problem free until now.

Sounds like the carb needs to be rebuilt. I know you cleaned it, but pay close attention to the high speed and low speed jets. If clogged at all...spit/sputter/rough idle.

Maybe. Both jets and any hole we could find was clean after we were done. Another thing I forgot to mention. This may actually be normal, but before I put a new plug in it and cleaned carb I took the old one out and cleaned it with a brush, got it pretty darn clean. After running it for short periods of time in hopes of blowing old stuff in carb. I pulled out the plug again, lots of carbon deposits on it already. Also prior to the cleaning and plug change, While trying to turn it over it backfired into the air intake.

Did you change the gas filter?

Didn't see a gas filter.

Jets clogged. Mine was doing the same thing last year. Cleaned both jets, and its running better than new.

The jets were clean.

Like said before rebuild the carb, I did mine for 18 bucks. Then tinker with the fuel mixing and throttle screw. I got online to find out exact turns on the screws.

Check to make sure that the carb intake boot to the airbox is tight. Also from the carb to the head

I don't know much about 4 wheelers but I had something like that happen to me. Come to find out it was my choke switch was messed up. I believe the guy said it was running to rich for two long. It did like yours slowly got worse till it wouldn't even start up. Got it changed out and works great now.

Non ethanol gas is still not good enough..The gas we get these days is junk buy you some "star-tron" enzyme treatment..

Just as a follow up.I took it to a certified dealer and they found that the petcock was the problem.. They cleaned the carb (even though we did it) and found a faulty petcock valve. They replaced it with a new one and it ran like a Honda. buck_buster.haha.Thanks for the info guys..

Also as 300gr mentioned the gas filter change... I think the gas filter is in the petcock....

As I was scrolling down reading my first thought was petcock.The filter is in the petcock.The petcock on these is renown for going bad.I have an Eiger basically the same machine.Mine did the same thing.Same fix.One bit of advice is to run some sea foam in it periodically.That will keep the carb working like new and keep the valves clean.That stuff is amazing and I could tell you some amazing stories about it.Also it is good measure to install an inline filter also because the petcock filter is a first stage filter.my $.02

Mine does the same thing. only it runs great when warm. when its cool it misses and sometime backfires. I don't have time now to work on it but the dealer said the timing was off. I didn't know you could change the timing but he said you could. That may be your problem

I've got a Zuki that will only run correctly on non-ethanol hi-test.