Basic jetting starting points

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  • oRGie

Posted May 27, 2003 - 04:43 PM


I've read so much about jetting my heads spinning :D

so I'm about to get my hands covered in fuel and muck about with the carb, zorst, airbox lid to see what happens. some posts say its well worth it, but others seem to just have problems..

starting point is 2002 wr426f euro model, airbox baffle removed, lid intact, standard jetting, zip-ty fs, stan euro exhaust, no insert to play with. Bike currently starts well, runs well, but feels restricted, like its got more potential lurking. A bit of hunting at constant 3/4 throttle on tarmac roads, nothing major.

I've ordered a stock yz426f needle and plan to put that in my wr to see for myself the difference. But I need to have an idea of what other jets and which sizes I may need to have on hand to experiment with, so any feedback on the following greatly appreciated..

q1 - what can i expect to happen when i put the zy needle on clip 4 into my wr ? will i need to change any of the other jets ?

q2 - by taking off the airbox lid completely will that make my mixture lean over the full throttle range or ? will going to a stock yz needle take care of that or which jets will I need to be looking at changing to compensate ?

(taking out just the airbox baffle made the bike run much more smoothly, thats what convinced me to try all this out)

q3 - fitting a very open competition muffler, does that also lean out the mixture or ? and again what jetting changes will be needed to compensate ? or again is the yz needle going to take care of the change ?

for some reason i'm left with the feeling after reading all the jetting posts i can find that taking off the airbox lid completely and fitting the very loud comp muffler will require me to fit the stan yz needle on clip 4 and go down to a 162 main which doesnt seem right if the lid and zorst are both going to lean out the mixture :)

thanks for any help with my stupid basic questions, hopefully getting some gas on my hands will lead me to the road of jetting enlightenment :D


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