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Discussion Starter · #1 ·
My cousin has a 2008 Z400 and I have a 2004 KFX400. We have the exact same mods done (as far as we know, got them used) except; the Z400 has 2 Bros M7 slip-on, FCR jetting 168M & 45P, 14 tooth, KN power lid. While the KFX has a full HMF, FCR at 165M 42P, 13 tooth, no lid. With the two bikes being damn near same thing, the Z pulls wheelies so much easier. It almost seems like his front end is lighter. We keep switching rides trying to figure it out but have no luck. Figured I'd see if anyone here has any ideas.

P.S: I tried running the same jets but mine ran like doo-doo. Mods in sig.
 

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The kfx may be a little lean? I'm running a 175m, can't remember the pilot i think 48? Yosh full, Um box no lid, fcr, drze gasket and cams. I thought it'd be a real rich mixture, but it's running better than ever, and the plug is a nice tan.
 

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Discussion Starter · #3 ·
I thought the same thing. But then with my 42P, my screw is out 1/4 turn. I can turn it in all the way with little change in idle. So, I was thinking going to a 40P. With the main I went up to a 170 and had little change. The KFX runs great, it just doesn't pull the front up as easy as the Z. What was the change with the frames?
 

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what size and kind of front tires are on each machine? if they're bigger and heavier on the kfx it will make the z lift the front end easier
 

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Ya, by looking at your heavy a$$ tires in your sig, I would say it's that. Especially if his has stock tires on. How about cams? Do you guys know for sure that they are stock? And ya, a bike running a little lean will feel alot quicker and lighter to throttle response.
 

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Must be the hood man :lol
 

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And you did a port and polish on stock displacement you may have just lost some power there. Does he have full skids?
 

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Discussion Starter · #10 ·
Big block is on the way to compliment my port and polish. Also, his is P&P'd on stock displacement as well. No, he does not have any skids. My fronts are 22" Raxr2's on aluminum rims. His are 21" ITP's on steel. We cant figure it out. Maybe it's a combination of a few things (tires, skids, compression, etc). Or, since we both got them used, there could be a different piston in his (thats the only thing we haven't replaced on ours).
 

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You'd have to tear both down, see what you both have. You may have low compression, the skids certainly don't help. There's a ton of variables. Even the different port jobs could effect them greatly.
 

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Discussion Starter · #12 ·
"There's a ton of variables", I think that's it. I know mine is stock size piston with stock compression. I'll need to inspect his.
 

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Check how much compression you are making w/ a tester as well. If you're low, there could be other issues to deal with.
 
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