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Discussion Starter · #1 ·
ok I bought a hmf slip on for my 07 ex. what main jet should I use? I bought a 152 and a 155 and a 40 slow jet. will that work? I only have 1 inch holes in my air box lid other than that it is all stock.
 

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What is your stock sizing??? Welcome to the site!
 

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Hello and welcome!
 

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my stock main is a 95 and slow jet is 42.i put a 105 main in and slow jet the same with the full exhaust.should be keihin jets.
 

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welcome to the Forums!! are you speaking about a 250EX or 300EX either way that IMO is way to big on the main.
 

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Discussion Starter · #6 ·
my stock jets are in it 148 main 38 slow jet. I do all tight trail riding no top end needed I dont get the bike out of 3rd gear.
 

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Discussion Starter · #7 ·
oh its a 400ex sorry
 

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Well with a 400ex the 152 and a 40 pilot should be alright.But you might need a 42 pilot.
 

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Also just remove the box lid.With a stock filter it needs as much air as possible.
 

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I dont know billy if he does a lot of dusty trail riding i wouldnt take the lid off, too much dust will stick to the filter. Just my opinion, but your right about the filter needing all the air it can get.
 

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Well then get a cleanable filter.
 

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Discussion Starter · #13 ·
yeah, I'm planning on getting a k&n filter in the near future. right now I am running the stock filter with the cage removed. just thought it would breathe a little better.
 

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Make sure you get an outerwears cover. but as far as your jetting the only way to tell if they are correct is to run it if you feel any lack in power on the topend then go up on the main jet, 40 is plenty big for the pilot. If you have some weak feeling power in the mid throttle your going to have to drop down a clip on the needle. I would say your probably going to end up with a 160 main. Keep us posted
 

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Discussion Starter · #15 ·
I will I should get my jets in a couple of days I will let you know how it runs.
 

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Good luck man.
 

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Discussion Starter · #17 ·
ok I got my hmf slip on and my jets today. I threw the 155 main in and the 40 pilot and its a night and day differance my quad runs great now. no bogging or starving on top end im happy with the results.
 

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Great Glad to hear it worked out now you need to do a plug check just to make sure you have the right jetting. get a new plug, a couple. warm up the quad riding it around nothing wild the find you a good long straight away open her on up and when you get wound out shut it down pull in the clutch and coast to a stop or just stop, lol pull the plug and see what the electrode color is, you want a nice light to medium tan almost the color of cardboard or coffee with creamer. if its too light or white step up the main or put the air box lid on if it's too dark remove the lid or jet down one size.
 

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Discussion Starter · #19 ·
ok will do i'm going out riding 2morrow.
 

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Discussion Starter · #20 ·
I did a plug check and its running a little bit rich but its not cutting out or anything. I still have the 152 main but its better to be rich than lean right?
 
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