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So I have done the exhaust mod and now want to change my air cleaner and do snorkles or the air box mod and jet my machine , I think the jet size say 160 is .160 inches so going up to a 165 should be a good start but my manual says 500 has a 150 and the 400 has a 160 ? is this a misprint or does the 400 have larger jets ? also should i put the pilot up 5 from 40 to 45 ?

thanks
 

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it is possible for a smaller engine to need bigger jets. jetting is not an exact science. there are so many variables. filter, snorkel/s sizes, elevation, exhaust, etc. Go up 10 and start there. you may have to jet down or up but starting fatter is safer.
 

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400 has a 34mm carb, 500 has a 40mm. Totally different carbs, totally different jetting. If your going to do snorkels and exhaust mod you cant say X jet will work. You have to test AFTER you get EVERYTHING the way you want it, Snorkels, exhaust, filter, ect. You wasting your time trying to guess. Depending on your snorkel size, number of bends, how long they are, can all change your jetting. You just have to do all your mods, then jet it accordingly. The exhaust wont affect jetting nearly as much as the intake side of things. Testing is the only way. I cant tell you how much time you can save by using a wideband. AEM has one for 170 bucks and it will save you about 10 trips into your carb. If you like to mod your atvs they are more than worth the money.
 
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