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83 XR200A Idles too rich with pilot screw all the way in. &%$#@!..

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Hi I have no idea why it is doing this..  I have tried adjusting the float lower, the manual calls for 12.5mm and I found it idles ok around 20mm, but the fuel screw still has to be all the way in for fastest idle (telling me the polot jet is too rich?)

  What could cause this?  Could it be a worn needle jet? The pilot jet (#35) and the main jet (#102) are stock.  I really don't think I should put in a smaller pilot jet.. right?

When the float is set at 12.5mm, it runs, but won't idle steady.  I can adjust the idle screw so I idle at 8-900 rpm, but if I hit the throttle and let go, the rpms jump to about 2000 and stay there.  I can slow it back down to about 800 again by quickly holding the stop button and letting go.

Some people have suggested air leaks, but I can only see an air leak making the bike more lean.  Plus I did a good check for them anyway and found none.  With the bike's float adjusted way lower than what it's supposed to be, it seemed to idle and run good.

Any info is greatly appreaciated.

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Rich can only come from a few places, in the pilot circuit:  clogged main air jet, or leaking choke circuit.

 

You need to remove all the jets, including the main air jet (which is probably partially clogged, causing your rich condition) and fish some fishing line and spray cleaner.

Remove the choke, clean and polish the chamber and plunger, replace the oring if applicable, and try again.

If you have a fuel or air screw, inspect it closely to see that the tip is not broken off.

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I agree with checking your fuel screw for a broken tip.

I believe a #35 is the smallest Keihin pilot made.

I assume you're measuring the float height at the proper point on the float if you have a manual you're going by.

Be sure you're using the choke lever correctly. That what you think is choke off is really choke on.

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Hi there, thank you for your replies.  OK so I don't think I have an air jet...  if I do have one maybe i'm overlooking something.

It's off an 83 XR200 A.  The carb is Keihin PD32...

The carb is very clean.  And it's since been cleaned again just to be sure.  The main jet is new and the pilot jet is surely clean.  Oh, the pilot screw is brand new and I double checked that it is the same as the old one I took out.

The float height is being measured from the carburetor body, where it mates to the float bowl.  And I'm measuring to the bottom of the float.  If I set it to spec (12.5mm)  the float sits about level with the carb body.  I have managed to lean the idle a bit by lowering it to about 20mm.  It just doesn't look right though...  The mechanic at Honda told me the float should look horizontal to the carburetor.

Yes I am surely using the choke right.

I also tested the float needle valve for leaks and it is working fine.  I used a clear plastic hose to measured the fuel level when the carb has gas tank hooked up, and it looks fine.

Does anybody think it might be a worn needle jet and jet needle?  I tried returning float level to 12.5mm (spec) then dropping the needle to from 3rd groove to second then to first, and this helped but only a small amount.

Honda sells the needle and jet as a package and they don't have it available anymore for 83xr200 anymore.

In the manual the carburetor's venturi diameter is 26mm.  I am not sure how to measure this because the carb tapers from a circle to a smaller oval shape in the middle.  Does anybody know how to confirm I have the right carburetor?

 

 

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You are changing around factors that have nothing to do with the pilot circuit

Ignore needle

Ignore main

Ignor float once at 12.5mm

Pull choke apart and inspect

Pull main air screw (located in bell of carb input) and inspect it and passage

Pull fuel screw and inspect

 

STOP GUESSING

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Some old carbs my look great and adjusted perfectly, but do not run properly. They just need replacement.

Make sure valve adjustment is correct and engine oil is not over full.

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Hi what should I inspect with the choke.  It's just a plate controlled by a lever.  When the lever is down the plate goes horizontal, so I guess it's working right.  Please let me know if there is anything to look for.

I don't have an air screw.  Just a pilot screw.  I don't see anywhere else fuel can come from.  The air filter is new and properly oiled.  There is nothing blocking air flow or anything. (It runs better with air box off, but still rich!)

What I do know is that it is too rich at idle because I can always get a faster idle with the pilot screw all the way in, and if I back it out it will stall if I don't turn in the idle screw.

I've searched around on the internet about this and all I can come up with is that I should go down a size on the pilot jet, but I really don't think that is right.

If a worn needle and jet couldn't leak enough fuel to cause this at idle then I just don't know where to go from here.

I really don't want to give up and by a new carb.  I think that any part that wears out in the carb is replacable right?

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Oh also the valves were recently adjusted, but i will check them again later today.

Thanks again for everyone's advice.

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Ok I've figured it out.. the needle valve is leaking enough just to raise the fuel in the bowl.  This puts more pressure on the needle so it won't leak anymore and come out the overflow, but the fuel is too high and it runs rich.

I gotta try somehow to fix the needle valve seat somehow because they are no longer available for replacement...

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