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Discussion Starter · #1 ·
Attempting to fix a problem tonight opened a whole new can of worms. Motor runs great except for one problem...when going slow or idling, if you try to give it a lot of gas quickly it will stutter and seems to backfire through the exhaust(can hear a pop out of the hmf muffler). Thinking I needed to address the pilot system I dug in tonight after work...

Took the brass colored top off the carb and made sure the holes in the slide were enlarged to 1/8", which they were. Tried moving the clip on jet needle down one groove to richen the mixture, no noticable difference so I moved it back.

After reassembling and starting the motor again there is an extremely high idle. My pilot screw is 2.5 turns out and at this point hadn't touched the idle screw. I believe it is running very lean but what do I know...I don't see fuel coming up out of the jet needle as I did before. If I cup my hand over the intake on the carb the idle goes back to normal and sounds great, can even rev the motor without any problems.

Took the bottom cover of the carb off and inspected the float, seemed to be in spec. Took a look at my pilot jet, which was marked 50. Interestingly, the 45 that originally came with the motor had bigger ports than the 50 did, I thought a bigger number would give more fuel? I think I will switch back to the 45 pilot jet to try and richen the mixture to maybe eliminate the stumbling at 1/8 to 1/4 throttle.

Now, no matter what I do I can't get the motor to idle normal without my hand restricting air flow. Messing with the idle screw does nothing. I've double checked the choke and I'm relatively sure it isn't engaging. I tried testing pressure on the fuel inlet like the service manual said but couldn't produce any pressure. I'm kind of confused because it says if it doesn't hold pressure to insepct the jet needle and seat/o-ring. But the jet needle is on the other side of the carb, there is no way you could build pressure and hold it since it is vented to the outside world. I must be missing something. BTW, I re-attached the carb to the airbox and made sure that the boots were tight, didn't change a thing. It also seems that the little free play in the thumb throttle I used to have is gone, but the throttle plate appears to be closing all the way.

Someone please help! Something is wrong!

CJ
 

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Make sure the cable is not stressed can you turn the handlebars left to right without the idle going up if it dose you have stress on the cable.
Start with the simple things it helps me.
 

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Yeah, check the throttle cable up by the rigth handle bar. I had a similar problem and there is a adjuster for the cable up there. It's a little screw and a bigger one that adjust the cable. Mine problem was that part of the cable actually broke when I crashed and didn't no it because they are in a rubber casing. I fixed it for now by tie wrapping that broke part to the handle bar. Works great until I get a new cable.
 

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Discussion Starter · #4 ·
Well I went to start it this morning and it all the sudden started idling fine, but then went back to idling high. I think something is up with the throttle like you guys are saying...even through the throttle plate in the carb looks closed if I push on the bottom of it with a screw driver the idle stays normal - thanks for the tip.

CJ
 

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Discussion Starter · #5 ·
It was indeed the throttle cable! I wish I hadn't messed with the idle screw now...but oh well.

I took it for a spin and the bigger pilot jet really seems to have helped my problem. The bike has much better response down low. Thanks guys.
 
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