Noob with poorly running 84 KDX200

[travisb]

Hello,

I recently bought a 1984 KDX200. The bike started on the second kick (from cold) when I bought it and ran ok.

This week, I had the expansion chamber repaired - inside cleaned, dents removed, outside repainted. The pipe had quite a few dents, but the bike has started relatively easily, idled ok and had decent throttle mid and upper rev range response. At the same time, I installed a new throttle assembly and throttle cable.

Since I reinstalled the refurbished pipe,the bike runs very poorly. It does not want to rev and bogs excessively. It will not idle. It seems like the mixture is very rich.

I also found the air filter was new, but completely dry (!). I have since oiled it and made sure there was no excess oil on the filter.

My carb has a #135 main jet and a #40 pilot. The pilot appeared to be clogged, so I cleaned it.

I removed the air filter as an experiment to temporarily add more air, but there was little change.

I am suspecting a jetting problem but think I should start with a compression test. The kick start lever seems to push too easily.

Edit: should the carb slide have a needle protruding from the center bottom? Mine does not. (Edit: Cmsnl microfiche shows a needle PN 160091152.)

Thank you for any help or advice,
Ben

[JL4049]

Lack of a needle in the slide will make it run ridiculously rich. Yes there is supposed to be a needle. I'm surprised you got it to run at all at anything other than full throttle!

[Jaguar]

taking the dings out of a pipe will not greatly change how it runs like you have described here.
Make sure you order a needle clip if a new needle does not come with one.

[doakley]

Forget the pipe, not the problem. While installing the new cable you lost the needle. Find it. Bike won't run without.

[KDXGarage]

wow

I hope you find it

[travisb]

Thank you all for the inputs.

Bikebandit lists the OEM needle. I am also going to call Sudco.

[travisb]

The OEM jet needle is back ordered. "JETSRUS" has a needle jet 5DP7, with similar but not exact dimensions.

5FJ57 (OEM)
(a) 57.5mm, length
(b) 25.5mm, distance to taper...D1-D5 are tapers in mm at 10mm increments)
D1 2.516
D2 2.516
D3 2.443
D4 2.222
D5 1.596

JETSRUS' closest jet needle 5DP7 has:
(a) 57.6
(b) 26.4
D1 2.512
D2 2.512
D3 2.440
D4 2.259
D5 1.580

Has anyone tried a different jet needle?

Thank you,
Ben

[BillyWillicker]

That needle is a hair richer. Try it. You may need to run a smaller pilot with it and at the most extreme the next size smaller needle jet.

[travisb]

Just an update...the jet needle arrived from JETSRUS today and I installed it. The bike runs about as well as I remember, although it seems slightly rich at idle. The sheared needle and clip were still on the throttle slide. The clip was in the top position, so I put the new needle in the second position from the top to compensate for the new needle's 0.9mm longer distance to taper. This could be contributing to the richness at idle, too.

[BillyWillicker]

Not really. I figured it would be richer at idle. Hence the smaller pilot suggestion.