'85 R rich midrange(or so)/plug fouling...please help

[DixiePlowboy]

I installed a #145 main jet in the stock carb on my '85 R and I'm now getting a tannish-brown plug color on a full throttle "plug chop". My problem is now in the 1/2 throttle range. It seems to be running rich, and has fouled a couple of BR8ES plugs real quick when ridden slow. I have lowered my needle (raised clip) until it's at it's leanest setting, but I still have the same problem.
When ideling, opening the throttle to 1/2 or so results in a sputtering/loading up kind of sound. If I keep it "cleaned out" when riding it, it seems to lessen the symptom, but if I ease around for a few seconds, it needs to be cleaned out again.
I've noticed(just barely) that the very tip of the needle has been nicked or chipped. Could this be the cause of my seemingly rich(sputtering) mid range and plug fouling?

[J.D.]

My Husqvarna 250(2 stroke) used to do the same thing to me. Never did figure out the problem, but as long as I had it at full throttle, and 2nd gear or above it was fine, never fouled a plug. Try riding 5 feet in first gear and it would foul a plug EVERY time!

[Truckster]

It could be the needle, but not the tip, it could be the wrong one now...

Jetting is a science!!! 8 yrs of racing MX/Enduro/Trials etc I gave up and went 4 strokes! I even went 4 stroke when road racing.. :s

[tony_250r]

If the plug is "tannish-brown" you are in the good.

You said you get a "sputtering", that sounds like it's too lean.

A rich mixture with the correct oil content will carbon foul the plug. Carbon fouling looks like ["dry fluffy black carbon deposites"], not "tannish-brown".

A richer mixtrue is required at lower elevations, and or when the weather is cold or humid. A Leaner mixtrue is needed when the weather is hot and or dry, and at higher elevations.

I would move the needle clip back to the middle postion, then work your way to the rich side, not the lean side. If the nick is in the tip of the needle, it won't cause that problem. You can buff it out with cocus cloth. If the nick is in the side, the needle and seat won't seal.

[DixiePlowboy]

tony_250r
I'm getting the tannish-bown color on a full throttle run.
My problem is in the part throttle range where it's "loading up" and fouling plugs. If I check(or pull it because it's fouled) the plug after part throttle operation, it's wet and dark.
Are you saying that raising the clip will aleviate part(1/2 or so) throttle loading up/wet plugs/fouling? If so, I'll give it a try.

[tony_250r]

You are "wet fouling, too rich", go down on the main jet i.e., lean it out.

I would still run the clip in the middle position, I think you might pick up torque that way, instead or RPM. Or one knotch up from the middle, on the lean side. See how it runs and then adjust.

[kimmer250r]

If you are getting a brown plug at top end then do not change your main jet. Your main jet has nothing to do with your midrange. The needle is what controls your midrange. Find a needle/jet chart online and figure out what you need. Go to www.carbparts.com and look at the keihin carb tuning and needle listing to give you more details on which needle you need. Good luck.