90 XR600 jetting

90 XR 600 riding at sea level

stock engine/carb/exhaust with airbox snorkel out and NOTOIL filter element.

The manual lists 165 main for 88 to 90 bikes. All others list 152 main?

Mine is jetted 165 main.

Is this rich enough for the open airbox at sea level?

What pilot is best?

Looking for a proven baseline setup.



Going up one size oon the main may help. The main jet really only controls wide open throtthe. A larger pilot jet can really help with starting.

I've always found the the needle clip position makes the biggest difference. However, the steps are rather large. I doubt that just opening up the air box is enough of a change for a richer position. You should try a richer clip setting and see how it works for you. Every bike is slightly different in how it reacts o jetting settings.

Id hafta say Id go one size larger on the pilot, and add a thin washer under the neelde to get a half step of rise, or richer on the needle. Id not go bigger on the main yet unless you do the WOT jetting test first. A too fat main robs top end power when to rich. Luckily, the XRs arent picky about jetting at sea level. Not until you get into high altitudes like where I live, 7420 ft above sea level. I have a pipe, UNI filter, modded airbox, and a 610cc kit and at 7420 i am at stock jetting plus one step richer on the needle. But the higher you get the leaner you need to be.

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