2002 mountain cat 800 No start

[Mccl6927]

Hello, new to sleds but I’ve been working on engines a while.

I’ve got a carbureted 2002 mountain cat 800 that absolutely will not start when cold or if it’s been sitting for a day. If I put some gas down the spark plug hole and put it back together it will start right up and runs fine. After that it will start just fine first pull all day long.

I bought the sled this way and the previous owner said he had the carbs rebuilt and it didn’t fix it. I also pulled the carbs apart and cleaned them, they looked clean and new. I even inspected the reeds and couldn’t see anything wrong. I don’t know much about reeds so I don’t know if you can see when they are bad. There were no cracks or worn spots though.

Any suggestions on how/where to attack this problem?

 

[hansenmac]

Maybe check your compression, i had a sled with a bunch of miles and it hated to be started the colder it got. Just not enough suction through the carbs to pull enough gas in.

 

[Gunit111]

Choke cable/plungers set correctly? Leaky water trap tubes? Cold compression? Stale fuel?

 

[Readymedic]

Check your impulse line. On those motors you can/t really see it unless you have the carbs off. It runs too your fuel pump. That's what pulls fuel tank to the carbs etc..
Not only make sure its hooked up, but make sure it is in hooked to the correct spot of the fuel pump. There will be two fuel ports and one for the impulse line. There will stamped letters on the fuel pump. If someone rebuilt the pump or had it off, it could easily be not hooked up correctly.

 

[Mccl6927]

I will do a compression test. Fuel is fresh. We’ve run it for 3 seasons now like this. I’ll also go through and check everything else mentioned in the next few days.

 

[kiliki]

Check your impulse line. On those motors you can/t really see it unless you have the carbs off. It runs too your fuel pump. That's what pulls fuel tank to the carbs etc..
Not only make sure its hooked up, but make sure it is in hooked to the correct spot of the fuel pump. There will be two fuel ports and one for the impulse line. There will stamped letters on the fuel pump. If someone rebuilt the pump or had it off, it could easily be not hooked up correctly.

Make sure this line is not cracked too.

 

[Mccl6927]

So compression at 20° F was 125 and 115. Fuel is fresh non ethanol 92 octane. Water traps tubes seemed okay as there was fuel in them and both fuel lines, so nothing was leaking out. I replaced the impulse line, it seemed fine except it had zip ties as hose clamps. After putting it all back together it started after five pulls so I think that fixed it. I will find out for sure tomorrow. What should cold compression be?

 

[kiliki]

So compression at 20° F was 125 and 115. Fuel is fresh non ethanol 92 octane. Water traps tubes seemed okay as there was fuel in them and both fuel lines, so nothing was leaking out. I replaced the impulse line, it seemed fine except it had zip ties as hose clamps. After putting it all back together it started after five pulls so I think that fixed it. I will find out for sure tomorrow. What should cold compression be?

compression will very for altitude and gauge so if you are over 110 and within 10% of each other it will be fine. make sure you test it warmed up.

 

[Gunit111]

125psi is fine. The 115psi is the point where cold starts, start to become a little harder. 105psi and less is where cold starts become difficult.

The bigger concern is 10psi difference between the two. Not a problem yet, but getting close.

Are the choke plungers set properly and are they working when you flip the lever. Snowmobile chokes have three positions; off (lever 90 degrees to the cable), half (lever straight out and 90 degrees to the off position), and full (about 30 degrees beyond the half setting). Having the correct warm idle speed is critical to choke operation. Float height is also critical to proper choke operation.

 

[Mccl6927]

Started with 5 pulls this morning so I’m thinking replacing that impulse line was the fix I needed. The hose was intact with no holes or cracks but I think it was worn and leaking at the nipple. Thank you for the advice!

I’m still going to look into the choke adjustment. I’m curious on how these work. Is it like my old Chevy that needs the choke on for 5-10 minutes or is it like my chainsaw and only needs it to start? I’d hate to leave it on too long and wash the cylinders out. Any good links on how to set it properly? I’ll do my own research too.

When doing a compression test I did notice one cylinder was a little oily and the other looked dry and had some crusty carbon deposit. Maybe new rings this summer.

 

[Readymedic]

Good to hear its running!!!