XR600 Needle Jet Adjustment

The bike is stock except uncorked and it seems like the midrange throttle is a bit lean. Main 165, pilot 65 (air screw 2turns out), plug is light greyish color.

My question is the needle same as most bikes where the clip is raised or lowered? Also what are the chances of reusing the gasket on the top of the slide or should I look for a new one first? Thanks.

If my memory is correct; it is a clip to raise and lower. The gasket is reusable as long as its not damaged or distorted.

A bit late but Thanks. The slide Gasket held up fine too. :ride:

After lowering the clip (raising needle) it runs much smoother. Roll'on is more responsive and the hesitation when grabbing a handful is all but gone. Definitely not a rich condition so may go up one on the main.

I would be surprised if your bike isn't already bordering on rich. Getting a useful plug color is tough with today's reformulated gasoline and it will probably look gray even when the mixture is right. The stumble when snapping the throttle open from a lower RPM is endemic to the carburetor design, not jetting.

Also, it's a fuel screw, not an air screw.

hey guys, hey HT, long time posting, anyways....

first here...what exhaust and or header do you have on your 90?

Im thinking I might be lean now on my 88 with powercore 4 and stock headers, stock for non 88-90 I had to dicth my stock setup cause too many pits and holes and leaking all over the place.

So my question is this: is a 158 main too lean for this setup? I went back to 3rd clip needle position stock, even though fmf says 4th clip, I was way rich all along midrange, and was blowing black smoke even at idle.


try a 160 main?

is there anything other than exhaust and headers on 88-90 years that would still necessitate a 165 stock main?


P.S. what would a lean main feel like? slow to get up to speed? what are the tell tail signs your lean?

I bought mine used in 1992 and it is all stock except for the exhaust baffle removed along with a twin air filter. The plug and tail pipe used to be a nice tan color, now with the fuel these days the plug is light grey.

My regular riding buddy yesterday said there was no black smoke or excessive fuel smell from the previous settings and he spends a lot of time following the pig:ride:. It runs much better in the midrange so I will probably stay with the needle position for now. Thanks for the info on the FUEL screw HT, I thought that was the case but wasn't 100% sure.

Christian, I am no expert so can't help with your particular situation. On mine, there was an occational surge at freeway cruise speed that is why I suspected a lean condition.


thanks jon,

I forgot about the surge at speed, I dont have that and my gearing is 5teeth down from stock to 45 in the back, just feels like Im wringing out the bike a bit to get there....

Ill do some tests, maybe some chop tests if I feel up to it, my bike does run better now, so Im happy about that.

Not to mention I was getting about 25-30mpg the way I was, but then again im heavy on throttle and stuff...

cheers and thanks for your time, enjoy your ride! im very happy with mine, FINALLY!


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