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Discussion Starter · #1 ·
rebuilt the motor in my z440 sno pro this fall, with the heads milled .015", and slight port clean up. i'm checking my plugs all the time to make sure it burning right, my plugs look good, but my pistons are clean all the way around the edge. aM I not running a high enough gas octane or... not sure what this means.
 

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how many mile since rebuild!sounds normal though.my sled was like that too after rebuilding!really if you think about it tour plug is in the center so combustion starts there!at least thats what i believe to be true.
 

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Discussion Starter · #3 ·
just over 600miles on the motor so far. From what I was told, the perfect jetting and fuel should have the piston all black on top except two little spots on the intkae side by the transfer ports.....
 

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Where is your timing knob set?
What jetting?
What notch is the clip in the needle?
Are the cylinders still nicasil no sleeves?

I checked my timing running and my mark runs 1 degree retarded, so I run the knob at 0 which is one click safe. I could click to +1 and still be fine with no less than 93 octane. You want to run at 0 degrees advance at NLT 91 octane. Your timing may be off (advanced) a degree or two and not know it. This would burn the fuel faster and not show any or minimal piston wash. I ported and flowed cylinder heads and anything else I could fit on the flowbench for 7 years in a race shop. I have over 8000 hours of experience on the flow bench. A slight port cleanup could affect your jetting. You may have to jet up and adjust your needle accordingly. I found that mine is pretty sensitive and easy to find the jetting "sweet spot". I am running 320s with the clip in the center notch. My pistons are dark with a slight wet on the edges. I run the BR9EYA's. They run the nice "lunchsack brown" I have no bog and it pulls from when I can the throttle till it hits top end on straightaways. I have never had a bog-very smooth. Turning the knob up will not benefit in the trails or on the lake. It is for sno crossing with higher octane/race gas in short bursts. When you find your timing, do not move the knob more than +1 degree( 1 degree advanced after you see where your timing is). As the temp cools down to 10 or less, you can back it down a couple clicks and save changing jets, but power will be down SLIGHTLY, but noticable(plugs will also be darker). I leave mine set at 0 degrees( because my mark show advanced 1 degree), 320 jets for hard running in trails-I mean hard running, but flippin the throttle a lot to keep fuel to it and the lube pump pumping. You have oil injection, right? I used Klotz oil, have for 15 years and never had a problem with it. I have started this year using Amsoil Dominator oil because I ride my sleds hard most of the time. I have not seen any problems yet and don't expect to. I have never run Cat injection oil or APV oil in my sleds. You are probably running close to the mark on jetting and okay, but going a little richer doesn't hurt to get some wash on the piston. I would like you to be able to see a little more on the piston. I hope this helps
 

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Discussion Starter · #5 ·
mines the 2000 z440 sno pro, it doesn't have the timing knob that you can turn, all timing still has to be done on the stator plate, stock jets are 330's, i'm running 300's with the needle in the middle, and the cylinders are still nicasil.
 

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Well, a lot of the same applies. Timing will need to be verified. Set piston at TDC with a dial indicator and mark flywheel with a sharpie. I drilled a small hole in the crankcase housing and marked it. Put the timing light pickup on the plug wire and run the engine till it is warm. Shut it off and remove the drive belt. Do not over rev. Slowly rev it to check it. I checked mine at 5000 rpms at verified the mark. It will line up with your mark as it flashes. If it is advanced, you will have to compensate with the stator plate adjustment. Some timing lights have a dial on it so you can see if it is advanced or retarded. If you are within a degree, you can jet up if it's advanced and move the needle. If it's not right on, move the stator plate so it's at 0 TDC. A plug reading is good as well. It helps to verify timing so you know where you are at.
By milling, you brought it up to the 01 up specs squish-wise with no change in port timing. If your compression is at 135 both cylinders, you will need to run premium. Shoot for 93 octane.
I think 300s are too small. 320s are just right in mine. I saw some burnt piston edges with 300s in mine at 20 degrees.
 

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Too much wash means your rich...nothing more complex than that...

SLOWLY and carefully jet down until you get the wash your looking for... The fanner might like a little more fuel than the liquid sleds (i.e. more wash showing on your piston).
 
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