Engine will not come down to idle still......

13 replies to this topic
  • BrandonW

Posted June 12, 2002 - 07:03 AM


Posted about this a couple of weeks ago, and I am still experiencing the same symptoms.

When riding, when I drop the throttle, it sometimes hangs about 250-300 rpm's high. Sometimes it will then drop by itself, other times I have to crack the throttle a time to two before it will drop.

I have taken the carb out, and determined that I am running a 45 pilot, and 172 main. I talked to the guy at the local Yamaha shop, and he said that is the jetting he is running, except that he has YZ timing and a YZ needle.

Whilst in the carb, I tried cleaning all jets and orifaces. I also ensured that I do not have any air leaks on hoses outside of the carb.

So, if I have recently replaced the slide plate (it is not cracked or placed in backwards) the jetting is supposed to be right, and I have no air leaks from hoses outside of the carb. What is left? Is there gunk in the pilot circuit that I am missing?

I took out the plunger and polished that up, and made sure that there was nothing on/in/around the diaphram. What/where else is there to be looking?




  • Brian_in_Long_Beach

Posted June 12, 2002 - 07:25 AM


You're lean on the pilot circuit. Try richening the fuel screw a bit - if you go too far out on the FS then go to a larger pilot jet.


  • racemile

Posted June 12, 2002 - 07:32 AM



I dont know anything about jetting, but, usually a hanging idle is a sign of being lean isn't it?? This would have to be something in the pilot circuit I would think. I might try messing with the Pilot Screw. Try going out some. I am sure the others may know more about this than I do, but, if you go out two turns without fixing the problem, then there may be some jetting changes involved. What position is you clip in? How does the bike run other wise? Stuck/sticky throttle cable?

Just suggestions, don't know for sure



Posted June 12, 2002 - 07:38 AM


I had the same trouble and it turned out to be slightly frad throttle cable. Just a few strands was enough to hang it up.

  • BrandonW

Posted June 12, 2002 - 07:43 AM


I have been monkeying around with the pilot screw. I have backed it out at least 2 turns, so much that I think that I am dumping unburned fuel. Header pipe gets all red when I really back it out, then I start turning it back in.

Other than that, the bike is a rocket. No complaints at all. Mid through WOT, the bike is responsive and quick. Economy is decent, as I get from 80-100 miles before I have to switch to reserve.

What is the needle clip position? Good question. Will have to check that out. As far as sticky cables, I am guessing that could be an issue. When I dorking with it this weekend, I was making sure that the throttle was not hanging up, and that I had about 1/8th of an inch of free play in the cable. I DID find about 3 or 4 strands that had burred on the throttle cable. I bet that is my issue.

Any seconds to that motion?


  • Rich_in_Orlando

Posted June 12, 2002 - 07:59 AM


I think MUDSAW may be right. (How's that for taking a stand?!) A 45 PJ is NOT too lean (I'm running a 35 PJ and my idle is just fine, thank you :) ). If you are seeing frayed cables, then it's time to replace them anyway. You don't want to get stuck miles from anywhere because of a broken throttle cable.

  • Terry_in_Reno

Posted June 12, 2002 - 08:53 AM


Have you checked to see if the slide plate is upside down? This is a common error.


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  • Brian_in_Long_Beach

Posted June 12, 2002 - 12:23 PM


What needle, needle clip & PAJ are you running with that 35 Pilot Jet?


  • Rich_in_Orlando

Posted June 12, 2002 - 02:54 PM


EMM #3
PA Screw 1/4 turn out = 45 PAJ
155 MJ
160 MAJ
60 SJ
1/2 sec APJ squirt

  • freestyle111

Posted June 12, 2002 - 06:15 PM


check to see if rubber o-ring on end of fuelscrew is missing or not seated properly .sometimes they get turned sideways when you thread fuelscrew into carb.also make sure accelerater pump rod isnt corrode or frozen.spray a little wd40 on it too ensure that its moving smoothly.

  • freestyle111

Posted June 12, 2002 - 06:22 PM


brandon,check you email.

  • rob1980

Posted June 12, 2002 - 07:23 PM


I found that when initially jetting my 250, if the needle clip position is too lean, or too higher clip, it can cause a hanging idle in a properly jetted pilot circuit. If all else fails, try droppimg the clip position one notch maybe.

  • dominator426

Posted June 13, 2002 - 07:25 AM


Have you checked your ignition timing? Have you tried going leaner on the pilot instead?

  • BrandonW

Posted June 13, 2002 - 08:11 AM


Well, here is what I am going to do. I think that my problem is based on my frayed throttle cable.

I called around, and the Service Shop at the Yakima Yamaha has the ability to rebuild cables as long as the sheath is still in good repair. I am going to ride in the poker run in Naches this weekend, so I am going to take off out of Wenatchee a couple of hours early on Friday, hit the Yakima shop by 5. They said that we can have that thing replaced in less than 1/2 hour. So, I am going to do that. If the problem still persists, then it will be more exploring of the carbs innards.

B from Chee


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