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In my 02 500 HO, I replaced the 152 main with a 155 and replaced needle w/new one, thinking now I could have put the 160 jet in it, The engine runs a lot smoother throughout the whole power range. kit is a bit expensive but works pretty good and comes with good instructions
 

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Possibly.Since you opened up the exhaust, it probably is sucking in more air and you'll need a bigger main jet to compensate for the lean fuel mixture. Do a reading on the spark plug and see , if it's any more than dark tan-black, it's too much.
 

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Won't hurt to got to the bigger main and try it. You should be able to feel and hear if it runs better or worse. Also try doing a drag race against another similar machine before and after each change to see if it helped or not. The dynojet kits definitely work!
 

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I have the 155 in mine w stock exh. Its good in summer here but i bump up to the 160 when its cold. Dynojet kit also.
 

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I put a 167.5 in my '05 400
Runs great , generally ride btwn 3500 - 6000 ft
 
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