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Coughs and Dies

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I'm at my wits end here. I've got a 1995 XR600 that I can't get to idle without the "cough and die" happening. It's got a UNI filter with the airbox snorkle removed and a Supertrapp with 9 discs. I've adjusted the valves and had the carb off and all cleaned out. I've had three different pilot jets in it (65,68,70) and adjusted the air screw out in 1/2 turn increments (starting at 1/2 turn out) all the way to 3 turns out with all three jets. It doesn't seem to make alot of difference if I run it at 1/2 choke either. Any help with this would be greatly appreciated. It is dualsported and it's very frustrating to have it do this in a line of traffic. I love the bike otherwise and if I can get this glitch solved it will be perfect. Thanks in advance.

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I'm at my wits end here. I've got a 1995 XR600 that I can't get to idle without the "cough and die" happening. It's got a UNI filter with the airbox snorkle removed and a Supertrapp with 9 discs. I've adjusted the valves and had the carb off and all cleaned out. I've had three different pilot jets in it (65,68,70) and adjusted the air screw out in 1/2 turn increments (starting at 1/2 turn out) all the way to 3 turns out with all three jets. It doesn't seem to make alot of difference if I run it at 1/2 choke either. Any help with this would be greatly appreciated. It is dualsported and it's very frustrating to have it do this in a line of traffic. I love the bike otherwise and if I can get this glitch solved it will be perfect. Thanks in advance.

Not to point out the obvious here, but just in case (Hey, we've _all_ been there...) how is the gas? Old? "Lacquer-ey"?

If you unscrew the drain plug, and then turn on the gas, is it brown and smell like turpentine, or essentially clear, and smell like fresh gas?

Just a thought...

:banghead:

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When you say cleaned the carb, did you just spritz it with carb cleaner or did you pull it off and completely disassemble it give it a good douching with carb cleaner and then blow the passages out with compressed air? It sure sounds like its got something in the pilot circuit.

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Ok I may be a dummy for saying this but my 2004 CRF450 started doing that and It was the ac pump rubber diaphragm. I had put stabilizer in in over the winter and the rubber got dry-cracked. I replaced it after getting a tip on it, and it was the fix. Like $14 with discount. I don't know about an XR but the issue sounds the same. I did check the gas, carb/jets ... first and none of it fixed it.

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Yeah it's all new premium gas in the tank. The inside of the carb was fairly clean when I had it all apart.

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I took the carb off and disassembled it all then shot carb cleaner through all the orifices. I didn't soak it in cleaner nor do I have access to compressed air.

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May be a air leak where the intake manifold is bolted to the head.

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A buddy of mine has a 1995 XR600 that was giving him the same grief. After years of on and off trying to figure out why his jeting changes weren't having the desired effect, he pulled the carburator apart and discovered that one of the o-ring gaskets had been pinched at the factory, and was leaking in air.

He got the caraburator overhaul kit from Honda. He eliminated all possible flaws when he did it himself. It has run perfect since.

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I checked for air leaks around all the carb boots and intake manifold with it running and a can of starting fluid with a little straw on the nozzle. I couldn't get any change in the motor at all. As far as the pinched o-ring idea I've already had the carb off and completely disassembled on my bench and everything looked fine. It's been suggested to me that low compression could be causing this. Does this sound feasible to anyone? I'm really grasping at straws by now and I'm ready to start over with all the possibilities and go through them again.

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I'm at my wits end here. I've got a 1995 XR600 that I can't get to idle without the "cough and die" happening. It's got a UNI filter with the airbox snorkle removed and a Supertrapp with 9 discs. I've adjusted the valves and had the carb off and all cleaned out. I've had three different pilot jets in it (65,68,70) and adjusted the air screw out in 1/2 turn increments (starting at 1/2 turn out) all the way to 3 turns out with all three jets. It doesn't seem to make alot of difference if I run it at 1/2 choke either. Any help with this would be greatly appreciated. It is dualsported and it's very frustrating to have it do this in a line of traffic. I love the bike otherwise and if I can get this glitch solved it will be perfect. Thanks in advance.

Can you give more info? Will it idle for a few seconds before it dies? When you say coughs, is it like a backfire? Does it run okay just above an idle?

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It will run anywhere from 5 seconds to 1 minute depending on which pilot jet and where the air mixture screw is. About 1 minute is the best I can get unless I turn the idle up excessively high. When I turn the air mixture in or out it doesn't seem to have a real profound effect on the way it runs. When I say coughs I'm not talking about a "pop" or anything out the exhaust, it's coming back into the airbox. A cough is about the best description I can think of. I wouldn't consider it a "backfire" or a "pop". At anything above an idle it runs fine (160 main, nice light brown plug color). Thanks for your help with this everyone.

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My 89 xr600 was doing the same thing this is what I did

Adjusted valves

cleaned air filter

new plug

fresh gas

cleaned carb , torn all apart and blew out passages

and what finally fixed it was when I turned out my fuel mixture screw, if changes to that screw doesn't affect the way it runs I would clean that circuit again . Replace the screw if it looks damaged, that fixed mine ,and you are right theres nothing that will make you madder than a bike that dies at a stop sign then starts back up hard .

The next thing I was going to check was if my stator was weak.

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Typically when they belch back through the carb like that they'er too rich on the idle circuit. ITs probably not the jetting. You've got a piece of dirt in the PAJ (primary air jet) circuit. The hole for that is one of the little ones in the intake bell of the carb.

You need to access some compressed air and prefferably one of those air guns with a rubber tip you can butt up against the carb and really put some pressure on the circuit and blow what ever is in there, out.

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okay here we go.... I have had 2 bikes brought to me recently with the same symptoms and was amazed to find the same solution on both, considering one was a 4 stroke and one was a 2 stroke.... Try this!

Pull the carb off ( again... I know its a pain but I think this will work.) Take the jets out of the carb. Get a wire brush ( preferabley a clean one)....

Now pluck a single bristle out of the brush.. and use it to clean the tiny passages in each jet. If you dont feel any resistance put a small bend in the bristle. Work it around a few times so you know it gets the passage clean. Thats it.. It worked for me on both bikes after I had tried literally everything else I could think of... I couldnt believe it. I had used carb cleaner, brake clean and compressed air, (cursing and prayers too haha)

Give it a try!

Good Luck!

dave

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Hey Shawn Mc, you may be on to something there. When I had the carb off and was shooting carb cleaner through all the orifices, I remember the three little brass looking holes on the airbox side of the carb intake bell. I think one of these must be the PAJ circuit to which you were referring. I shot carb cleaner through all of them and all but one seemed to blow out somewhere else(some other orifice in the carb). One of them didn't seem to "come out " to any place. I'm wondering if this is the PAJ that you mentioned and it is plugged. Do you remember if all three of these holes "went through" to someplace else in the carb? Do you remember which of the three holes was the PAJ circuit?

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Also mcgvr86, when I take the carb back off I'll do your wire brush bristle cleaning thing. I really don't want to take it back off for a third time. Also to answer an earlier question, yes I have adjusted the float level. I'll get access to compressed air some place when I have it apart and really blow it out. Thanks everyone for all the ideas and suggestions, these forums are a great resource and are full of information.

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yeah, no point in cleaning a carb if you cant blow the hell out of it.....get a cheap compressor for like 100 bux.....or a real nice deluxe one..........it will more than pay for its self.

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I know its a pain.... I didnt figure it out until at least the 3rd time, but look at it this way.... by the time this is over you will be able to take that carb off in 3 minutes while sleeping! Seriously though, I went through alot of different things before finding the problem. I even took the coil in and had it checked at the dealer ( on the wr400) so when the 2 stroke came in and had the same symptom, I did this after the "standard" carb cleaning didnt work. It ran fine after that.

Let us know what you find. dont give up. you will figure it out!

dave

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I did have a 650 L that did the same thing, it was the CDI box, if I wiggled the wires or tapped on the box while running it would shut off, it would only act up at idle, but it did spit back, I could hear it in the airbox.

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