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Bike is popping and runs like crap at idle

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I went to an indoor track last month and the whole day I was trying to solve a problem with the carb, what was happening was the bike would not idle, so to keep it running i had to keep hitting the throtle (it is not idle screw). when i was riding it would run great accept when i let off the gas it would backfire like crazy and it still would not idle. I changed the pilot jet to try and richen it up (to compensate for the colder air here in minnesota it was about 50-60 degrees in there) and it got better but it didnt solve the problem, and the problem was still to bad to be a jetting issue. I then thought there is a vacuum leak in the carb to engine boot, there was not. now that I think about it, the hot start could have been adjusted incorrectly but i cant ride it to try and figure out if that is the problem... so has anyone else had these problems? and if so, what did you do to fix it?

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I had a very similar problem when the the joint between my mid-pipe and silencer was loose. Make sure all the joints of your exhaust are tight. Hope this helps.

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How far was your fuel screw turned in? If it is turned in too far it doesn't really matter if you go bigger with the pilot jet, the fuel screw will still choke off the fuel supply at idle.

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Yep, check hot start cable, and plunger. Check pipe mounts, check carb boot clamps, look over your air boot for a crack or tear, if not check carb for correct jetting, make sure jets are actually clean...

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Check your carb boot again I just had this problem with a 03 crf450 I just picked up. I cleaned carb and re jetted and turned out to be an air leak. Double check and use a flashlight.

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I know the valves are closing up tight, clearences aren't perfect but its on my to-do list, but their not that far off... It's not the mid pipe, I also checked it for cracks, I know it isn't junk in the carb because i just cleaned it. I am really convinced it is the hot-start. I have checked the seal on there and it seems good. So it must be that it isnt adjusted right, I will find the problem and let you know so that hopefully this thread will be helpfull to someone else

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I had exactly the same problem and my mechanic said it sounded like bad gas. I pulled the tank, drained all the gas and that in the float bowl, filled up with fresh gas and within a quarter mile or so it smoothed right out and runs great. Lots of problems around here with premium gas getting stale due to high price. Also the alcohol in it dosn't help. I now run regular and add an octane additive.

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I've been struggling with pretty much the exact same problem, and the bike was also getting hard to start. I thought that it might be the valves so I just finished adjusting them. Made a big difference with the starting issue, and the bike does run better, but the trouble at idle and the popping during deceleration is still there. Brand new air filter, I just took the exhaust off and put it back on and seem to be good to go there as well. So I am assuming this has to be a fuel issue, I'm going to experiment with the pilot jet and richen it up based on where I am at....I'll let you know how it works out for me though.

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The bike also has a tendency to stall at super slow speeds if you draw the clutch in.

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How was it running before you cleaned the carb? and when you cleaned the carb did it run fine afterwards?

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Carb is clean, checked everything out, I'm thinking that I need to change out the pilot jet. It runs excellent in the mid, and even better at WOT.

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I ordered the pilot jet the other day off of here, hopefully it clears up. I'll test/tune it the next time I hit the track and post up with the results.

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Yep, check hot start cable, and plunger. Check pipe mounts, check carb boot clamps, look over your air boot for a crack or tear, if not check carb for correct jetting, make sure jets are actually clean...

Yeah do this, mine was doing the same thing. I cleaned the carb out really good, including the jets. I bought a different fuel/air mixuture screw...I forget who makes it. I think Sunline? or something its so you can adjust with your fingers. Put that baby on there and fiddled with it and no more popping when I left off the throttle. Mine was only doing it when in gear and deaccelerating. I still does a tiny bit but you really gotta listen for it. Before hand it sounded as if someone was firing a pistol in the distance haha

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this jet was completely plugged up, I did manage to clean it out but bought a new one and installed it anyway. after soaking the jet well, used some sustained high pressure air on it till it blew out, then soaked and sprayed it some more. it worked for me, til I got the new one in ...

pilotjet.jpg

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