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I'm working on a friend's 02 mxz and was wondering what jetting is safe for about  -30celsius? I'm running 480 in my 01 without any trouble so would the same be ok 4 his?
 

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Jetting on the 02's are different because of some major changes in pipe and timing.  Leave the 02's at 520n's, they do not like to be jetted down as far.

GLH
 

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in my 02/800 i'm using 500's with the timing advanced and have still got a good burn
 

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In my opinion 520 N's are way to rich, look at the chart below and see that a 520N is actually equal to a 560, check chart below, many guy's are running 480's around here. Like I posted before I'm running 440 mains and no filter with a RKTech head.
Here is a chart on the differences bewteen the ''N'' and non ''N''. The number on the right is the fuel flow. This came from Snowtech, a couple of issues back!!!,

Mikuni Jet Spec
Main Jet Fuel Flow
400          352
420          372
440          392
460          410
480          430
500           453
510N = 540 466
520N = 560 481
530N = 600 491
540N = 620 515
550N = 660 538
560N = 700 572
 

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I also agree that the 02 is jetted way to fat, as for major changes in the pipe, the volumes are pretty close to the same and the resonance of the pipe is the same as the 01, when you put an 02 exhaust on an 01 motor on the dyno the power remains the same and so does the BSFC so what that means is that both pipes draw on the engine the same. The 01 with the updated changes has the same timing as an 02 and both sleds for most general usage below 2000' can run regular 500 main jets or less. Also saw on another post about the lean midrange, there are a lot of reasons you see higher midrange temps, but what we have done to richen the midrange is to use Yamaha plastic needle spacers which come in .010", .015" and .020" thicknesses, these will take care of any midrange leaness. They cost about 45 cents apiece and are the best way to richen midrange and by far a lot cheaper than needles or any other so called fix.
 

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Do you guys do anything with the pilots and dropping the needles? I picked up  a stock 01 800 (all updates)and ride at 1500 to 3500ft and think it will be rich. Never do wot for more than 15 seconds because of the terrrain. Should be safe dropping down pilots and main considerably, yes?
 
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