04' 900 1M chain case help

Sep 5, 2017
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Hi all, ill start by saying I'm relatively new to sleds I've only been riding one season. I'm looking at a 2004 MC900 1M 159", a massive upgrade from last seasons Indy 500 LC 136".

So the guy I'm buying it from has said it seemed to be skipping teeth in the chain case due to running it dry last season and heating it up. He replaced the chain and the issue went away, but has since re surfaced.
I have photos of both the upper and lower gear/sprocket.

1st question, is that a logical scenario?
2nd, could there be something else causing the skipping, if so, what?
3rd, how difficult is it to replace the gears and chain?
4th, what gearing and chain should I go with if my riding style/area is mostly low elevation off trail riding?

Any advice or opinions would be extremely appreciated!

Hoping to get a hold of this sled for $900, which seems like a good price but I have no idea being new to sleds.

Thanks in advance for any info!
 

Readymedic

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Nov 6, 2013
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The drive bearings do go, but they are a simple fix.
Definitely needs new gears and and don't forget the oil. If he ran it dry, he was either an idiot or the gasket on the chain case cover leaks. Look for the fine rubber gasket. It's simply an O ring but a big one.
900 would be a good price as long as the engine is good. Make sure you do a compression test!!
 
Sep 5, 2017
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Thanks for the responses, didn't expect to see any that quick!

Yeah Idk how he ran it dry but thats what he claimed to have done.

He says he replaced the rear axle, if thats of significance.

Can anyone tell me the part numbers for the chain case gears and chain?
I've read 18/40 70P is a good setup, but I'm okay with just putting stock back in there though. I'm open to suggestions too!
I do alot of deep powder hill climbing and back country riding locally. We're expecting 3+ft this season like last season.
 

Idcatman3

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Thanks for the responses, didn't expect to see any that quick!

Yeah Idk how he ran it dry but thats what he claimed to have done.

He says he replaced the rear axle, if thats of significance.

Can anyone tell me the part numbers for the chain case gears and chain?
I've read 18/40 70P is a good setup, but I'm okay with just putting stock back in there though. I'm open to suggestions too!
I do alot of deep powder hill climbing and back country riding locally. We're expecting 3+ft this season like last season.

Good place for looking up part numbers:
https://www.countrycat.com/arctic-cat-parts

https://www.countrycat.com/arctic-cat-parts#/Arctic_Cat/2004_MOUNTAIN_CAT_900_GREEN_159/DRIVE//DROPCASE_ASSEMBLY_[79303]/3|~79319/3|~79319|~0738-939


26 1602-394 Sprocket - 43T
26 0602-453 Sprocket, 40T (Above 4,000 ft Alt.)

32 0602-973 Sprocket - 19T

23 0602-972 Chain - 72P
23 0602-968 Chain - 70P
 

Idcatman3

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So im assuming I'll want the 43 and 19, what chain? 72?

How difficult is the gear change?
Never been inside a chain drive before.
If I'm remembering correctly, that's right, the 72P chain. If you go down to the 40T lower sprocket, that's when you need the 70P chain. Changing stuff isn't too tough, just pay attention to how you take it apart, and put it back together the same way.

service manual with instructions is here:
https://support.countrycat.com/posts/1424389-2004-2-stroke-service-manual

page 8-47 is where the chaincase without reverse is talked about.
 
Last edited:

kiliki

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19/43 is a good stock set up do not go smaller than a 19 top gear. pay attention to the lower gear as it can be put in wrong. the gear has a larger offset on one side and this faces in. very basic set up i put the auto tension components in the trash an just use the jamb nut to take up the slack. only go finger tight on the bolt that takes up the slack.
 

sprockethead

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The SnoPro racers run there sleds with no chaincase oil. Don't want the drag that the oil creates. They only run the sled for a short time and do heavy maintenance on there sleds after every race. Maybe this knuckle head had heard this and decided to do this with his sled. Not a good idea for a sled that is ridden hard for a day at a time. I would for sure change out the driveshaft bearing (lower one) and maybe even the jackshaft bearing (top one) depending on how it feels. If the driveshaft bearing is bad what you hear ratcheting my be the drivers on the track. The lower bearing does go bad if left neglected and can do damage to your sleds tunnel also. Good luck!
 
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