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Well i've owned my Vstar 250 for like 4 or 5 months now and all i've mod'd on it is the back sprocket to a 40... and i've been reasonably happy with it ... but suddenly now when i run it for along while and get it good and hot then turn it off (say to get gas) and Start it back up ... it tends to Backfire on the First turn of the engine ... never while its running or idling or any other time ... just when you start it when its hot .... now from what i understand backfiring is the collection of gas in the exaust pipe that then blows up in the pipe... My Question is ... what do you guys think may be causing this. i haven't had my valves set since i bought it ...and its got 3500 miles on it ... i thought that might have something to do with it ... and also ... it seems like it got a good bit louder ... guess the backfiring has kinda moved some stuff out of the way in the exaust ..... i think there's like some kinda Cloth in there isn't it?
 

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I also did the sprocket change. with the 16/45 stock, I found coming down off of 55-60mph MPH in 5th it would backfire because obviously it was humming pretty good. Since I changed to 17/40, things are much quieter and less back pressure. Backfires can and will burn out mufflers for sure. I think you may want to make sure you are not running hot because of a too lean mixture too. Check the plugs and see if they seem burnt. You can also look at the muffler pipe coming out of front cylinder and see if its starting to lose the chrome and seem burnt. Goes without saying to stay up on oil level/ changes too. Air cooled engines heavily rely on oil for cooling as oil dissipates heat so if oil is broken down, heat will be retained and of course cause higher running temperatures.
 

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I also did the sprocket change. with the 16/45 stock, I found coming down off of 55-60mph MPH in 5th it would backfire because obviously it was humming pretty good. Since I changed to 17/40, things are much quieter and less back pressure. Backfires can and will burn out mufflers for sure. I think you may want to make sure you are not running hot because of a too lean mixture too. Check the plugs and see if they seem burnt. You can also look at the muffler pipe coming out of front cylinder and see if its starting to lose the chrome and seem burnt. Goes without saying to stay up on oil level/ changes too. Air cooled engines heavily rely on oil for cooling as oil dissipates heat so if oil is broken down, heat will be retained and of course cause higher running temperatures.
Well i've owned my Vstar 250 for like 4 or 5 months now and all i've mod'd on it is the back sprocket to a 40... and i've been reasonably happy with it ... but suddenly now when i run it for along while and get it good and hot then turn it off (say to get gas) and Start it back up ... it tends to Backfire on the First turn of the engine ... never while its running or idling or any other time ... just when you start it when its hot .... now from what i understand backfiring is the collection of gas in the exaust pipe that then blows up in the pipe... My Question is ... what do you guys think may be causing this. i haven't had my valves set since i bought it ...and its got 3500 miles on it ... i thought that might have something to do with it ... and also ... it seems like it got a good bit louder ... guess the backfiring has kinda moved some stuff out of the way in the exaust ..... i think there's like some kinda Cloth in there isn't it?
I'm hearing you. My 250 recently had the same issue. Turned out I had a small hole in the rear cylinder exhaust pipe under the center of the bike. Patched the hole and all was good. I believe the system was sucking in fresh air through this hole and igniting the left over fuel vapors in the line. By the way, the hole was caused by acid dripping out of the battery overflow line that runs down to this area of the bike. You might want to check your line to ensure you don't have the same thing going on. Best of luck.
 
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