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Discussion Starter · #1 ·
I have a 2000 ZR Sno Pro w/ a 2000 ZR 600 motor w/ twin black magic pipes that is running fat with 370/380 jets(380 on clutch side) in 25F temperatures. Does this seem reasonable? What does Black Magic recommend?

Elevation is at sea level
 

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Stock jetting for that motor was 340's, but you would use bigger jets for those twin pipes so what you have sounds reasonable. Unless you are running rich on wide open pulls, you might want to look at your needle settings. if you are running rich during normal trail riding conditions, raising the clips (which would drop the needles) might help a lot.

Also, make sure your chokes are not sticking, or that the choke cables are not adjusted too tight causing the plungers to be lifted a bit.
 

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What are you basing the rich mixture on? Plugs? Piston wash? Both cylinders the same? I'm running 360's at around 1800'. 370's for real cold temps. You're in the ball park, so shouldn't be too bad. Check ignition for proper operation, can sometimes look/feel like you're running fat when you have bad spark. Happened to me... then my stator sh*t the bed.
 

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25 degrees is pretty warm out your jetting down if you went up 2-3 jet size from what stock pipe would be. Which they are jetted from factory down to 0. I would say your a rich for 25 degrees you could drop down almost to stock if its 25 degrees out. I would rather have it rich then lean.
The other thing I would check is the oil pump setting. They are rich at the correct setting. How much oil is puking out the back of the motor where the pipes are?? If you having oil running out of where they connect to the motor pretty good sign your oil pump needs to be turned down. Rule of thumb I was taught was the oil pump lever shouldn't start to move until you have about the thickness of a credit card gap on the throttle lever and block. A lot of times theres no slack in the oil pump cable as soon as you give it throttle your pumping in more oil then needs to be.
 

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The quantity of oil from an injection system (within reason) shouldn't matter. There are alignment marks on the pump which should be matched at WOT. Those jets should make you run rich at 25F. Try dropping a size. I'm guessing there's a reason you're running different sizes and you know your engine, but plugs and piston wash are identical in my engine with the same size jet in each cylinder. Just an FYI. When she's dialled in you'll know. I can keep up with my bro on his zr800 no problem. Of course he's got about 100 lbs. on me... makes my stock EFI zr600 feel like a pooch. Perhaps I should also mention I'm running pods and ditched the airbox. Whether I'm pulling in more air or not, I couldn't tell you. Sled came that way and I love being able to swap jets in 2 mins. with that airbox out of the way. Enough reason for me to keep it that way.
 

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i run 330's on a ZR700 with black magic twins. 340's are too rich
Black Magic's recommendation; 350's, clip in 4th slot. it was fouling out plugs while doing 60 mph, and 6 mpg.
So their recommendation was on the safe side, real safe side.
 

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Before getting too carried away with the mains you may want to take a look at your mid-range. Every builder puts out iffy calibrations, sometimes so the bean counters will warranty them. I had a 2000 for a back-up sled in case my big-bore ever let me down, Cat really screwed the pooch on the B-case carb in the 2K Millenium sled and regular production. With a stock pipe I jetted 330 mains and leaned down the mids from the 9EGY-57 needles to 9DFH-60 and ran 56 grams of weight to put enough heat in the pipe. With BM twins I ran 340 mains and 9DFH-59's needles and never hurt it no matter how hard I ran it.
 

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Discussion Starter · #8 ·
I appreciate all the responses, but I just realized that I somehow put the wrong jet sizes down on the post. It was running fat at 270 and 280 which is insane right? I thought that I may have a bad main gasket so I put a new one on and it seems to be running way leaner. It's really snappy and starts on first pull now. When I give it full throttle it doesn't want to rev out so now i'm thinking it's the clutch weights. I finally found out that its a 98' motor on a 2000 sno pro chassis. I think it's the black magic pipes because it's just so erratic. Although, at one point last year I had to dialed dead on. It's one of those things where it always seems to be something. Thanks for the posts!
 
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