Can't get it to idle

Trails Boy · Post by **Trails Boy** » 11:03 am Apr 27 2012

Just got my own KDX and new to the forum

1987 KDX 200 it runs great other than the fact that it wont idle...

I know 2 strokes aren't supposed to idle long but every time I let the throttle down it dies... We've already tried a few of the basics (me and my club leader) we cleaned the carb, adjusted the idle screw and even with it all the way in couldn't get it to idle, replaced the 9 spark plug with a 7, cleaned the exhaust, and I just took the intake boots of to repair a couple of cracks in them.

My club leader took a look at the spark plug and said it was getting to much air in the mixture hence the repairs on the boots but I'm doubting thats going to fix the problem tho. I have a size 35 pilot jet at 2000 altitude is this right? Also theres not much power in the low end could this be part of the problem?

Any help would be great!

Also I would like to trade my stock exhaust system for an aftermarket exhaust system if anyone is interested.

Post by **SS109** » 11:21 am Apr 27 2012

Welcome to the forum!

I would check the left side crank seal (behind flywheel) to see if it is leaking.

Trails Boy · Post by **Trails Boy** » 11:49 am Apr 27 2012

Thanks!

Would it be leaking oil?

Post by **SS109** » 02:08 pm Apr 27 2012

Yes, it sometimes can weep a bit of oil there.

Trails Boy · Post by **Trails Boy** » 02:32 pm Apr 27 2012

I checked and it's not leaking...

diymirage · Post by **diymirage** » 03:25 pm Apr 27 2012

i would look to rejet the carb and see what happens then
(if the jetting isnt where it needs to be the bike will never run right)

there is a very handy jetting guide in the (you guessed it) jets and needles section

Post by **SS109** » 05:40 pm Apr 27 2012

Even though it isn't leaking oil it still can be sucking air. You can always do a leak down test to know for sure,

Trails Boy · Post by **Trails Boy** » 07:06 pm Apr 27 2012

Yeah I think I'll re jet it and see what that does.

How would I do that test?

I'm a newish mechanic (being 16) but I've done lots of small engine repair and general stuff on my dirt bike.

Trails Boy · Post by **Trails Boy** » 07:09 pm Apr 27 2012

Another thing is it doesn't have an air screw?!?

rbates9 · Post by **rbates9** » 07:25 pm Apr 27 2012

Pics?

Trails Boy · Post by **Trails Boy** » 08:34 pm Apr 27 2012

I'm assuming you meant of the carb?

Post by **SS109** » 09:28 pm Apr 27 2012

Man, I don't like them old Mikuni round slide carbs. Hard to jet and to get a good idle. I wonder if you could swap on a later Keihin PWK on that with little effort? The PWK is superior in every way.

Trails Boy · Post by **Trails Boy** » 10:36 pm Apr 27 2012

I don't have the money to get a whole new carb right now... :/

Post by **SS109** » 11:38 pm Apr 27 2012

Well, maybe someone had better luck with them than I did and can help you out. Might post up over on ThumperTalk as well as I'm sure some of the old timers over there should have some input on them. I'm not the super techno savvy guy when it comes to jetting and that is why I love the PWK since it makes it way easier!

Trails Boy · Post by **Trails Boy** » 07:02 am Apr 28 2012

I'll try that!

I'll look into getting a PWK later on...

Thanks for your input!

Post by **Julien D** » 02:28 pm Apr 28 2012

I believe you could swap out a PWK with little trouble, using the stock jetting of the E series KDX as your baseline. You could find a used one reasonably priced on ebay. 35mm is what you'd want. As for the mikuni, yeah, they are a real pain to tune. Still, assuming the circuits are all clean and the compression is good on the engine, it should idle and run out just fine. Are you certain the pilot jet and circuit are clear? That would be the most obvious cause. A guitar string and a can of air work wonders for clearing them out!

Trails Boy · Post by **Trails Boy** » 02:45 pm Apr 28 2012

Yeah there clean... I made sure of it.

It's stock jetting is 320 main and 25 pilot... It's currently 370 main and 35 pilot. Should I go back to stock jetting?

Post by **Julien D** » 02:58 pm Apr 28 2012

Trails Boy wrote:Yeah there clean... I made sure of it.

It's stock jetting is 320 main and 25 pilot... It's currently 370 main and 35 pilot. Should I go back to stock jetting?

Yeah, that's the first thing I would do. We can work on the jetting from there.

Sent from my ADR6350 using Tapatalk 2

Trails Boy · Post by **Trails Boy** » 04:24 pm Apr 28 2012

Okay sounds good.

Thanks for the help!

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