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Discussion Starter · #1 ·
i just bought this 2001 zr 440 sno pro. it had 850 miles when i bought it, i took it out and cooked the piston. guys said it was from runnin last years gas in it, so i replaced the two pistons and rebuilt the top end. all new gaskets. the onyl thing was the gasket set was for a 2000 zr 440 but everything lined up fine. i just recently cooked that piston again....and scuffed up my cylinder pretty bad. its been the same side every time too. the clutchside. i know when it was running right it idled at 4000 and took off at 6 which is right for this clutchkit i got for it i guess. but i have 300 mains in it. i was just hoping someone knew something about how to make some sense of this sled and how i can trail ride it without cookin the piston every time thanks.
 

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What a coincidence, I got the same sled, SAME PROBLEM it seems! Rebuilt the whole top end 2 years ago after cooking a piston (late March) with all new A/C parts (over $320.00), honed the cylinders, etc. It ran great all of last season, put it away with 1829 miles on it. Complete service on it last month and finally got the first ride in yesterday ( 1-21-07). I went 38 miles and it ate up a piston, was just crossing a road and hadn't been hammering on it @ all (since we've got very minimal snow to ride on anyways). I thought it had just fouled a plug so I took it out (recoil side) and noticed the electrode had no gap- NOT GOOD eekkk I put another plug in it and nursed it to my parents place and then trailered it back home. Haven't taken it apart yet, but with the small flexible light you can see the top/side of the piston has just flaked apart, it barely stays running and compression is way down. I'm thinking a piece of the flaky **** got on top of the piston & on the up stroke it bent the electrode.?? I don't run this sled WFO, just cruise and ride the bumps. Any ideas on what the hell is eating up our pistons? Priced a new one today @ the dealership and you can't buy just a piston anymore. It comes w/ rings & circlips (no biggie to me as I want it right). They are $ 107.00 bucks. Should be back together soon, it just sucks being it happened on the first ride of the year ! --Snotty 440 (was) :D
 

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Here is the deal guys. That sled was made for short bursts on a snocross track and is pretty tightly wound. Here is the settup you should use to trail ride it. First off you must run 92 octane fuel. Don't run anything less. If you have the owners manual there are two jet charts. One is for snocross and one is for cross country. Use the chart for cross country and jet according to the temp on the chart. Adjust your timing to -1 degrees with the dial. Last, install Jet needles J8-6FM2-60-3 (part number: 6506-174) If you do all of this then you shouldn't cook anymore pistons. You are obviously detuning it a little bit, but I have done this to mine and on the trail you cannot really tell the difference. Remember when jetting that being rich is always safe. All this info is from an arctic cat service bullitin I have.
 

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Here is the deal guys. That sled was made for short bursts on a snocross track and is pretty tightly wound. Here is the settup you should use to trail ride it. First off you must run 92 octane fuel. Don't run anything less. If you have the owners manual there are two jet charts. One is for snocross and one is for cross country. Use the chart for cross country and jet according to the temp on the chart. Adjust your timing to -1 degrees with the dial. Last, install Jet needles J8-6FM2-60-3 (part number: 6506-174) If you do all of this then you shouldn't cook anymore pistons. You are obviously detuning it a little bit, but I have done this to mine and on the trail you cannot really tell the difference. Remember when jetting that being rich is always safe. All this info is from an arctic cat service bullitin I have.
 

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Here is the deal guys. That sled was made for short bursts on a snocross track and is pretty tightly wound. Here is the settup you should use to trail ride it. First off you must run 92 octane fuel. Don't run anything less. If you have the owners manual there are two jet charts. One is for snocross and one is for cross country. Use the chart for cross country and jet according to the temp on the chart. Adjust your timing to -1 degrees with the dial. Last, install Jet needles J8-6FM2-60-3 (part number: 6506-174) If you do all of this then you shouldn't cook anymore pistons. You are obviously detuning it a little bit, but I have done this to mine and on the trail you cannot really tell the difference. Remember when jetting that being rich is always safe. All this info is from an arctic cat service bullitin I have.
 

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Thanks for the info, I did fill it with 89 octane & 1/2 a bottle of gas line antifreeze as it was only about 12* when we took off to ride. What does retarding the timing -1* do? I was told to leave it @ 0 ( but it's ate 2 pistons now, so I'm up for trying something else ) I dunno --Snotty 440
 

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<div class='quotetop'>QUOTE (snottysnopro440 @ Jan 23 2007, 08:57 PM) <{POST_SNAPBACK}></div>
.. What does retarding the timing -1* do? I was told to leave it @ 0 ( but it's ate 2 pistons now, so I'm up for trying something else ) I dunno --Snotty 440[/b]

I was told by member c-note to never, ever change that setting from -1. C-note also recommended setting that knob to -1 and then removing the knob so nobody plays with it "accidentally". Just my 2 cents worth of advice.
 

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<div class='quotetop'>QUOTE (sysanalyst @ Jan 23 2007, 08:22 PM) <{POST_SNAPBACK}></div>
<div class='quotetop'>QUOTE (snottysnopro440 @ Jan 23 2007, 08:57 PM) <{POST_SNAPBACK}>
.. What does retarding the timing -1* do? I was told to leave it @ 0 ( but it's ate 2 pistons now, so I'm up for trying something else ) I dunno --Snotty 440[/b]

I was told by member c-note to never, ever change that setting from -1. C-note also recommended setting that knob to -1 and then removing the knob so nobody plays with it "accidentally". Just my 2 cents worth of advice.
[/b][/quote]

I went to Race School in 01' and I owned an 01' at one time too (Got my pic in "Snowmobile" Mag just for being there too!). Anyway, per Greg Spalding, the guy who developed this engine at Arctic Cat- Run 92 Premium Gold from Ammoco (Which is now BP in MN). This engine was developed on this fuel.

Retarding the ignition keeps your combustion chamber's temp lower..... As does the higher octane. This is the "Safer" way to run the sled. But- If the sled has been raced; then the ignition box may have been re-programed with different ignition curves...... Sometime this means that they are "Hotter" then stock. So if you know how to check and ensure that you have a "Stock" ignition curve programed 0 or -1 are your safer bets.

These sleds were designed to be played with to find more HP. The higher the octane = a lower the internal temp in the engine = the more room racers had to play with the set up to find more HP.

Hope it helps guys!

Thanks!
7UP
 

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Discussion Starter · #9 ·
but heres the thing. i've had 300 mains it in, and i always had that timing box set at -2. well technically i guess i burnt my piston down from running bad gas. but what explains the second time, same piston. i completely drained the gas put premium from bp in. and went riding .....ran fine, then i made a lil trip and i was buzzin down the trail and my motor died.....started it up ran it down the trail after new plugs were put in and brought it home. did a test back to 95 compreesion clutchside again and about 130 on the other again. so i guess we could blame the first time on that gas but the second? there was a scratch on the cylinder i do beleive but the mechanic that looked at it said that it was fine. so maybe thats why it happened. but I dunno, it wasnt runnin lean or anything the edge of the piston just kinda sunk down, and the cylinder had a few scratches and dimples in it. i mean theres gotta be SOMEWAY to just figure out the problem of it right?
 

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<div class='quotetop'>QUOTE (gerdon @ Jan 24 2007, 07:30 AM) <{POST_SNAPBACK}></div>
but heres the thing. i've had 300 mains it in, ...[/b]
The 300's are mighty lean... try some 330's. They may run a bit richer, but will save your pistons. The next thing; are you sucking air into that jug? Perhaps a bad carb boot or something like that. Worse case; crank seal.
 

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yep , mine is a 99' that is set on + 2 BUT im running 114 oct. leaded fuel through it too slomo
 

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Got mine apart tonight and it needs a piston kit and the cylinder is pretty much shot also :( Got the dealership working on parts, will be in on Monday/Tuesday. Cylinder is going to be replaced, I've found a new A/C one ALOT cheaper than what the dealership's quote was. BTW, How do you check the ignition box to see if it's been re-programed? Thanks for the help guys, :thumbsup: --Snotty 440
 

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Guys these sleds were factory race sleds tuned for sno-X not trail riding. Chnage the needles to what Snowman said. Also never run anything less than 92 octain 100LL is better. If you have to carry octain booster if you question the fuel at all. Also 4000rpm idle for trail riding seems a little high.
 

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i ran 330's on 93 with my 2k sno pro...

when the temps warmed up to the 40's and 50's late in the season that thing ran like crap unless at higher RPM in the power band

but i never burnt up a piston ;)
 
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