blew up my 900

pano-dude · Jan 4, 2008

looking for some advise,

I bought an 04 900 162 king cat with vforce reads, twin cpi pipes and can. Airbox is gutted. 400main jets.

Took it out a couple weeks ago for the the maiden voyage and got 5km down the trail and it died! I did not even open it up yet??? when it died I opened the hood and there was antifreeze all over. Started at around 3000feet -15c.

Towed it back, pulled the heads and found the mag side melted the rings into the piston, pto not to bad but some scaring.

opened the bottom end to check for any shavings and found the both mag and pto bearing retainers had somecracks(why do they use plastic retainers???

so now I've got a new crank, jugs, pistons etc. Going to put it together but i don't want it to happen again.

thanks

ACMtnCat · Jan 4, 2008

Not sure but, 400's sound too small for your 3000 elev.

Double A · Jan 4, 2008

I would second that on the mains. Seems like you should be 440 or so. You might try raising the needles up a notch too. If that proves too rich in mid range you can always lower them back down. Get a holtzman vari flow or attac to compensate air temp./elevation. Whats the deal with th antifreeze all over?

pano-dude · Jan 4, 2008

that's what i said too.... not sure if it was to lean, got hot and boiled the coolant over??The anti freeze bottle had a couple of grooves in the top where the cap goes on so it may not have had a tight seal. Got a new one, cap and stat as well.
Not sure where the needles are set, did not look at them.
We unload around 3000 and top out at 7000ish, definately will go up a couple sizes to be safe.

Double A · Jan 4, 2008

at 7000' you will probably need around 400 mains though. Thats why (IMO) you should look at an easy way to adjust fuel (vari flow, atacc, etc.) without swaping mains on the trail. Just makes it nice and easy to keep your sled running well...and safer when riding low elevation. Keep your engine temps down to 150*. Ice scratchers are handy for keeping control of temp. on hard pack. Better luck this time!

Just my opinion.

diggerdown · Jan 4, 2008

Jetting was too small but also check the thermostate and the anti-freeze. It could have been frozen.

Meatman · Jan 4, 2008

especially with the reeds/pipes and can at that elevation i run 490 mag 480 PTO at sea level....ive maybe put 100 mi on it at sea level but the plugs have always looked good and never had a problem with it what were you pulling for Rs?

amery3 · Jan 4, 2008

Be sure to check out the thermostat too, these engines have a history of those thermostats going bad...I went 1.8 miles with my 800 and it blew up...stuck thermostst, no light even came on. Antifreeze all over could be from the coolant boiling in the engine and blowing out cold coolant out the overflow.

Regardless, 400's are too small.

Rixster · Jan 4, 2008

yeah your jets are way to small (lean) I am riding at 8000-10000 with twin pipes ans gutted air box. I run a 410-420 setup.
Also I didnt notice if anyone else said this already but the mag side is always hotter on that motor, Anybody that has modded one will tell you to run at least one jet richer in the mag side. Also they hate twin pipes. When you run twins you have a wicked LEAN spot in the middle. It only takes 10 minutes of riding down the trail at half throttle to burn it down. When you ride a trail with those pipes you have to constantly move the throttle to get enough fuel to it.

pano-dude · Jan 5, 2008

Really! damn it... it would have been nice if the fricken guy who sold me the sled would have shared that info with me! He dropped it off and said it's good to go!
That's exactly what happend I'm sure.
Expensive lesson i guess, I've never had a cat before. Always ran Ski doo.
I've got the stock pipe too, i think i'll put it back on and go back to stock. Some of the areas I ride to are 40km from where I unload, I don't want to burn down again!
Any info on what the stock clutching was or should be? I think the stock spring is in a box with the pipe, but I don't know if the weights were changed.
Thanks for the tip.
D

Rixster · Jan 5, 2008

Stock clutching is like this (if I remember right)

Primary
68-69 gram weights
yellow green spring

driven
53/55 helix or a stright 53
red white spring

In stock trim you should turn 7200-7400 RPM

This setup is for higher altitiude, if you are lower you might want to throw more weight at the primary, but this would be a good starting point.

If you keep your twins I would highly recommend getting some EGT's so you cna watch the temps.

pano-dude · Jan 5, 2008

what temp range should I expect to see and maintain?

Rixster · Jan 6, 2008

There are so many veriables on pipe temps. Twins, single, how far your probes are from the pistons, IT really depends on your setup. If your probes are 3-4 inches from the pistons, I think thats where they recomend to put them. Running down the trail at half throttle I would not wat to see more than 1050. running long pulls, at wide open throttle its not unusual to see up to 1300-1350.

r9559 · Jan 6, 2008

all good comments......... I will add my a few. Cpi recommends 460 mains (0-4000ft, 400's @ 6000ft) on a single which I have on my 900. Yours should be close with twins.
I run 370's @ 5-7k with no problems, I have ice scatchers which can save your motor from overheating on a icy trail. When your riding at lower elevations on the trail and you think your lean, run with your choke on half.
Good luck

CATSLEDMAN1 · Jan 7, 2008

Last One Standing

you didn't blow this thing up, you were riding it when it blew up, most piston failures and crank failures are the result of continuous over heating and cronic and worsening metal fatigue eventually leading to a pile of dust.

And that's why you get the guy saying, " I was just easy trail riding it when it blew". And you were,.............. but continued lean jetting without piston seizure, and or no piston wash, and looking for HP with lean fuel air mixtures, and underclutched buzzing harmonic vibrations with a contant touch of detonation, some of the best looking bling infected modified sled are really rolling junk piles headed for aluminum recycling. This model engine from arctic cat was lean lean lean out of the box and worse when guys started modifying them. This stout old cat motor is impossible to hurt with powerful rich jetting and a heart breaker to fix $$$$ wise when you let the thrifty gas mileage hp seekers jet them.

pano-dude · Jan 7, 2008

i have been out of sleds for a few years(kids), I always swore against pipes before, it seemed to me all the guys who did run them spent more time with the hoods open than riding.

I was not sure about the pipes on this sled but the guy who sold it to me said it was dialed, also other guys i talked to about the sled said no worries, the 900 is bomb proof?? I considered putting on the stock pipe before i took her out and now $2500 later i should have.

Thanks for the help everyone.

-MKlim- · Jan 7, 2008

i run 400 mains from 3500- 8000ft.. never one problem

pano-dude · Jan 7, 2008

odd, big difference in what everyone is running for mains.... do you run the 400's in all weather temps? Stock sled?

I'm definately going back to stock pipe and a can, to me the extra 10ish hp is not worth the chance of the lean mid range burn up.

lightening800 · Jan 7, 2008

jetting

i ran 390-380 with slp twins, reeds, gutted air box, timing key, rode from 6000-8000 never skipped a beat, jetted to 440 to run around home at 2200'.

blew up my 900

Member

Well-known member

Member

Member

Member

Well-known member

Well-known member

Well-known member

Member

Well-known member

Member

Well-known member

Well-known member

Member

Member

Well-known member

Similar threads