here's the prob. I'm working on a Arctic Cat 250, not sure of year model, but it has a new carb. It will run battery down trying to start, once started runs fine, kill it starts right back up, if within about five minutes. everytime I think I have it fixed come back next day to start and same thing, won't start. Bike had full tank of old gas, hadn't been run in about a month, and gas was varnishing, so I drained it and put 93 octane in to clean it out. Still no good. Pulled the carb off, went through it, thinking their was varnish in jets and bowl. Guess what, everything looked brand new. It's got fire because it will start after about 30 minutes of fighting it. I don't know what else to try, could the valve clearance cause this, surely not? I could really use some help on this one, any info would be GREATLY appreciated. Thanks

 

These engines where designed to run regular unleaded 87 octane gas , and if the valves are out of specs they can cause hard starting when engine is cold ; but usally make a popping/backfire through the intake or exhaust when valves need adjusting !

Check your airfilter clean and reoil if dirty.

But Sounds like it could be the choke not working correctly , easy way to tell is to pull the spark plug after turning the engine over a few times to see if gas is getting to the combustion chamber ; the plug will be wet if the choke is working correctly !

Try putting a new spark plug in before trying to start the engine , then if it doesn't start pull the plug and check for fuel on the plug ; if if's it's wet with gas try grounding the plug to cylinder head and turn the engine over to check for a good spark !

If this doesn't get it going check the valve specs for proper clearance and adjust if needed , this is all i can think of for now ; hope this help's ; and welcome to the forums !........

 

I'm sorta having the same problem. Is there a valve or timing chain adjustment that can be made? Mine does backfire when you let off after accelerating and just kinda lugs and bogs down. Lots of black soot on the plug and tailpipe too. I need a service manual I guess to figure this out.

 

Yes the valves are adjustable and the hardest part is removing plastics to get to the valve access caps , you have to remove the seat air cleaner and the rear plastics/fenders to get to them ; and there are two access caps on the head the one in front of engine is the exhaust valves and the one on the rear are the intake valves !

Not knowing what year model you have i'm not sure of the engine manufactuer , most likly it would be a Suzuki engine ; it would be alot easer with a repair manual to help you determine the engine make and step by step instuctions on the proceedure !

I wish i could help more if it's a Suzuki i have a manual that covers the 250 Suzuki engine , if not there should be someone that can tell you what the engine make is ; but we would need a little more info on the year and model !.....