New KDX owner with throttle problem

bajus22

Member
Dec 8, 2008
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0
Hey guys, I just picked up a 1987 KDX200. I took it out for my first ride. It started up no problem, ran great, lots of power. The only thing that bothered me was after riding for a bit, and coming to a stop (in neutral, or in gear with the clutch in), the idle would increase dramatically. If I let out the clutch a bit, the bike would return to it's normal idl for a second or three, and then pick up again. Riding down long hills, with the throttle closed, or after a wide open stretch, closing the throttle would still result running the high idle (even though the idle was set properly). Any ideas where I should start looking for the problem?
 

Dirtdame

Member
Apr 10, 2010
146
0
I am assuming that you have a Mikuni 34mm carb on it. Those did not have an air adjustment screw on them. Make sure that your pilot circuit is completely clean. If the jet is completely unobstructed and all the air and fuel passageways are clean and it still does this, try going up to the next size pilot jet.
 

bajus22

Member
Dec 8, 2008
80
0
I'll have a look, butI think you're right, it is a Mikuni. I'll take the carb out and clean the pilot circuit. Would a worn or sticky throttle cable cause this too? The idle adjustment screw seems completely useless on my carb. I had to adjust the idle with the throttle adjuster nuts up near the throttle grip. That was the way I set the idle.
 

bajus22

Member
Dec 8, 2008
80
0
Does that also mean I was running really lean when the throttle was closed and still reving? Would I still be getting enough oil?
 

Dirtdame

Member
Apr 10, 2010
146
0
Your bike won't blow up because of that. Make sure that there is a little freeplay in your throttle grip (maybe 3 or 4 mm). This will ensure that you will be adjusting your idle with the screw, and it also will ensure that the bike won't rev a bit when the bars are turned full lock.
 

bajus22

Member
Dec 8, 2008
80
0
OK, I took apart the carb, and cleaned it. The throttle cable looked to be in real rough shape, so I ordered a new one. I won't be able to test ride it until the week-end, although it did sound okay going up and down the driveway.
 

julien_d

Member
Oct 28, 2008
1,788
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Watch the cable routing very closely. When you install a new one, make sure you can turn the bars from lock to lock without losing any of the play at the throttle control. I keep about 1/8" of play in mine. Normally, if the idle speed is set with the bike cold, the idle will increase as the bike warms up. I wonder if that may be affecting you as well? The cable is certainly the first place to look. If everything checks out there and with the carb, then you're off to mechanical problems with the engine. Air leaks, reeds, compression issues, etc. Lets see what the new cable does for ya.
 

jabman

Member
Feb 8, 2010
5
0
so its a lean condition that causes the idle to shoot up

i thought it was a rich condition, my bike is like the one in this thread the revs shoot up on very small throttle openings and the tickover goes through the roof when coming to a stop with the clutch in :bang:
 

bajus22

Member
Dec 8, 2008
80
0
So where exactly should I be looking for an air leak? Is there a test to perform to see if I actually have one? And how do I fix it? Thanks for the help so far.
 

jabman

Member
Feb 8, 2010
5
0
air leak

yes i believe you need to get it started and idling then spray some wd40 over the carb to engine boot and see if the idle changes at all.
 
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