ReconRat Posted August 25, 2009 Report Share Posted August 25, 2009 (edited) A back fire is combustion in the exhaust. Timing off will do it, leaky exhaust valve will do it, and fuel in the exhaust pipe will do it. Is it now running too rich for some reason?Backfires at idle, heh? Is the throttle slide needle in the right place? As well as the throttle slide? Either would dump huge amounts of fuel into the cylinder at idle.If a carb has a blocked idle jet passage, it won't respond normally to turning the mixture screw. It will either do nothing, or turn too much to get anything.And if the throttle slide is stuck up too high, it won't respond to adjusting the idle screw, if it's the type that moves the throttle slide up and down. (Moving the needle in and out of the main jet.)edit: if the main jet was clogged before, the needle and slide may have been up too high to compensate. Once cleaned out, it may be releasing too much fuel, until it's once again adjusted properly for control of fuel at idle. Edited August 25, 2009 by ReconRat moar Quote Link to comment Share on other sites More sharing options...
ReconRat Posted August 26, 2009 Report Share Posted August 26, 2009 (edited) Ok, float position too. In particular, the chunky float needle that lets fuel go to the main jet and needle jet. The jet needle is the skinny one on the other side of the main jet and needle jet. Both control and regulate fuel. This is midrange and high end fuel, and either one out of position or condition would dump excess fuel into the cylinder at idle, and MIGHT be the source of backfiring in the exhaust, at idle. Edited August 27, 2009 by ReconRat Quote Link to comment Share on other sites More sharing options...
ReconRat Posted August 26, 2009 Report Share Posted August 26, 2009 Carburetor discussions and manuals:CarburetorsCarburetor Theory and TuningMikuni ManualKeihin Manual Quote Link to comment Share on other sites More sharing options...
bt's Posted August 27, 2009 Report Share Posted August 27, 2009 One easy way to check for vacuum leak is to start the avt and LIGHTLY spray starter fluid on the carb boot / intake boots / reed valve gaskets and see if the throttle picks up. Just don't over do it and don't do it when the bike it hot.What kind of atv is this??If you are cleaning the carbs, take care NOT to spray carb cleaner on the rubber tip of the float needle that shuts off the fuel to the main jet. It will dissolve and not seat correctly, leading to new problems. Quote Link to comment Share on other sites More sharing options...
max power Posted August 27, 2009 Author Report Share Posted August 27, 2009 its a 2001 warrior 350 thumper Quote Link to comment Share on other sites More sharing options...
bt's Posted August 28, 2009 Report Share Posted August 28, 2009 This reminds me of my buddies new KTM 525. He put pipes on it and rejetted it and it ran like crap. Turned out to be a cracked carb boot. Make sure everything is dry of gas on the inside of the motor as mentioned before and see if you can get it to idle with as little choke as possible to keep it running. Then try to leak check with started fluid.This shit sucks, I know, I am a loyal Banshee rider for the past 6 years Quote Link to comment Share on other sites More sharing options...
max power Posted August 28, 2009 Author Report Share Posted August 28, 2009 would a cracked boot cause it to back fire constantly? Quote Link to comment Share on other sites More sharing options...
Wheezle Posted August 28, 2009 Report Share Posted August 28, 2009 Yes Quote Link to comment Share on other sites More sharing options...
max power Posted August 28, 2009 Author Report Share Posted August 28, 2009 ah see, ah see. I'll try the starting fluid trick tonight. Quote Link to comment Share on other sites More sharing options...
bt's Posted August 28, 2009 Report Share Posted August 28, 2009 Yeswhat he said. Quote Link to comment Share on other sites More sharing options...
blake1221 Posted August 28, 2009 Report Share Posted August 28, 2009 ah see, ah see. I'll try the starting fluid trick tonight.Keep a fire extinguisher handy......Remember the Shadow? Quote Link to comment Share on other sites More sharing options...
max power Posted August 28, 2009 Author Report Share Posted August 28, 2009 Keep a fire extinguisher handy......Remember the Shadow? haha, true. I better wait till you get back. Wouldnt want you to miss out on the fun.Probably ought to do it in the driveway instead of in the garage too. Quote Link to comment Share on other sites More sharing options...
blake1221 Posted August 28, 2009 Report Share Posted August 28, 2009 I'm getting ready to take the 2 fiddy out to the Michigan Motor Speedway (696) to pick up the parts for da Hawk....wish me luck Quote Link to comment Share on other sites More sharing options...
bt's Posted August 31, 2009 Report Share Posted August 31, 2009 Any news on this front? Hopefully you dont come on here and tear me a new one for burning your bike down Quote Link to comment Share on other sites More sharing options...
max power Posted September 1, 2009 Author Report Share Posted September 1, 2009 ^ haha, no. havent had time to mess with it. Will get on it this week and report back. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.