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Discussion Starter · #1 ·
So here's the story.

I got a 2007 400ex off a friend, when he got it he was told it had cams (no specifics), had an HMF slip on, 40 idle and 165 main jets, and it has a crappy GYTR filter on it which I plan on replacing with a new K&N, other than that, stock.

He ended up losing an oil line or something, didn't notice, and blew it up. He then bought a stock head honed out to a 440 with 11:1 Wiseco piston and rings and installed it. This is when I aquired it... NOT knowing all the details until now.

After riding it the first time I realized it was no more, or not even as powerful as my 400 I previously had. I started researching and saw on RMATV the stage 1 cam says "not reccomended for big bore" stage 2 doesn't mention it, I don't know what kind is in it. Then I saw, while googling the internet and coming across a lot of 440 nightmares, with the big bore there are other things that need done, like a larger oil tank, oil cooler, cam chain tensioner, main bolts, jets, etc. I found out he did none of this.

I want to get this done right before I ride it anymore. I've never done, or owned a big bore before. What do I need to do/add/modify to make this 440 run right with no worrys? Also will 93 octane do? I don't have race fuel near me, may just use octane booster anyways. If it makes a difference, I only ride woods.

So far these are the suggestions I've gotten, I'd appreciate it if you tell me what you think and or what other suggestions you have...

1. Head studs from GT Thunder (I don't wanna do all that if I don't have to)
2. CFM Oil tank with cooling tubes, found on ebay for $159, looks pretty nice, supposed to lower 50 degrees.
3. Add an electric fan like from a 450R.
4. Change jetting to 42 slow 180 main (keihin) 2 turns out from lightly seated on the fuel screw.

Sorry for the long post, didn't wanna leave out any details, thanks in advance!
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