hotshot Posted March 12, 2004 Report Share Posted March 12, 2004 I am helping a buddy install new intake/exhaust on his Z400. I am very experienced with carb set-up and jetting of 2-strokes, but I have never owned or worked on 4-strokes. Can you read plug color the same as on a 2-stroke, and shoot for a tan color, or is testing a thumper a different ballgame? Any advice would be appreciated... Quote Link to comment Share on other sites More sharing options...
spoin39 Posted March 12, 2004 Report Share Posted March 12, 2004 Yes you can read a plug on a 4-stroke, what kind of mods exactly? If just a filter and slip-on, try a 150, stock should be about a 135-140. Quote Link to comment Share on other sites More sharing options...
Banchetta Posted March 15, 2004 Report Share Posted March 15, 2004 I've tried that numerous times w/ no results.....the best and easiest way is to do time runs....We ran my cousins 400ex down a paved road for about 500'. Have one guy running the quad and the other at the finish line w/ a stop watch...Make 3 runs, change the main jet, run 3 more times. Take an average of the 3 runs and you will see about .10 seconds per jet size difference...Which is about a quad length...If your 5 jet sizes off, then you'll gain .5 second, which is huge....Good luck. Quote Link to comment Share on other sites More sharing options...
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