XR4 jetting

Joined
Dec 8, 2000
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#1
I have a 2001 XR400 and im thinking about putting an FMF Power Core IV muffler on.
I also want to remove the snorkel but im not sure what the jetting would be. If anyone is running this setup or something very similar, any coments would be greatly appreciated. Oh, almost forgot, I live in central Missouri so I guess that would be close to sea level. Thanks in advance!

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Joined
Nov 12, 2000
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#2
162 main jet, 62 pilot jet, fuel screw @ 2 1/2 turns out! This is with an aftermarket exhaust and snorkel removed! I used this jetting on my old 98' XR400 and it ran great at sea level!

Garrett

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I get my kicks on a 2001' YZ426!
 
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Mar 30, 2001
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#3
that is the stock jetting for my 96 xr400. after i went to a 430 kit with porting and open exhaust, i needed to go to a 168. i left the pilot alone due to the supreme ease in starting. after about 12+ rides i decided to go to a 170, but the damn rod broke! to late! dunno how the 170 woulda performed.
but hey
!! i found almost 5 distributors for COMPLETE brand new xr400 engines!!hopefullythey wont be 1000$+. anyways dude try that 162 62 jetting with a new cpl new plugs. do plug tests at each jet rpm range and find out which sizes work best. usea new plug for each test, or your results will be screwy

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Joined
Dec 20, 2000
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#4
I agree with the 62/162. I ran this on my 98 with the FMF IV/2 pipe, snorkel removed.

another great site for XR info is the ww.groups.yahoo.com, XR400 discussion board, great source for info.

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Joined
Oct 7, 1999
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#5
I have elevation changes from sea level to 6k. I use 160/58 for jack-of-all-trades setting (opened up breathing and exhaust).

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TR

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Mar 17, 2000
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#6
SkinnyWheat, what do you think cause your engine to fail ? XR's typically suffer from bottom end failures when over modified and poor quality oil is used. But a broken crank ?
Are you sure the piston was installed correctly with the correct clearance ?

Regards
TR

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[This message has been edited by TR (edited 04-09-2001).]
 
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