crank rebuild 2013 RMK pro 800

[K1Dbilly]

I’m new to the snowmobile world but recently got a 13’ rmk 800 for cheap with a seized rod on one side of the crank. It has 1100 miles. I got a new crankshaft, fix kit and top end from Rev6 with all the gaskets. I plan on replacing the check valves and thermostat as well. I have some experience with 2stroke motors from dirt bikes and a jet ski. Just wanted to get some feed back on tips and things to look for while rebuilding it. I have read to turn the oil screw 2 1/2 turns to increase the ratio and that some people run 100:1 in the tank for extra lubrication after a bottom end rebuilt.
Any and all feed back is welcome as I have a lot to learn
Thank you

 

[ABMax24]

They're not particularly hard to rebuild. Make sure you have access to a service manual for that year to check bolts torque specs etc. just make sure you get the correct sealant for the cases and headbolts when you re-assemble.

Biggest thing I'd be concerned about is making sure the bearing didn't spin in the cases, if it did the cases are probably toast.

Reed valves probably need attention while you are in there too.

Check out the oil pump too, there's a cam inside them that wears over time that increases oil flow with throttle input. As it wears it decreases oil flow to the engine. The pump itself isn't serviceable, if there's any doubt of it delivering enough oil it might just be best to replace it too.

 

[K1Dbilly]

They're not particularly hard to rebuild. Make sure you have access to a service manual for that year to check bolts torque specs etc. just make sure you get the correct sealant for the cases and headbolts when you re-assemble.

Biggest thing I'd be concerned about is making sure the bearing didn't spin in the cases, if it did the cases are probably toast.

Reed valves probably need attention while you are in there too.

Check out the oil pump too, there's a cam inside them that wears over time that increases oil flow with throttle input. As it wears it decreases oil flow to the engine. The pump itself isn't serviceable, if there's any doubt of it delivering enough oil it might just be best to replace it too.

Ok, thank you. What would be the best way to check if the crank bearings are spinning? I’m assuming you would have to check it with the case split?

 

[ABMax24]

Ok, thank you. What would be the best way to check if the crank bearings are spinning? I’m assuming you would have to check it with the case split?

I misread your original post, I thought it was a main bearing that seized. In that case the outer race can spin in the cases, and the hardened steel race destroys the aluminum cases.

Yours was a seized rod, which won't cause that.

 

[K1Dbilly]

I misread your original post, I thought it was a main bearing that seized. In that case the outer race can spin in the cases, and the hardened steel race destroys the aluminum cases.

Yours was a seized rod, which won't cause that.

Ok that makes sense. Do you know if the check values are cleanable or just needs to be replaced? I’m sure once you pull them they are toast.

 

[ABMax24]

Ok that makes sense. Do you know if the check values are cleanable or just needs to be replaced? I’m sure once you pull them they are toast.

I'd just replace them, not worth messing around with.

One more item, check the oil tank cap and make sure it lets air into the tank, they've been know to plug and cause the oil pump to vacuum lock. Some guys used to use the smallest drill bit they could find to open a hole in them to guarantee they couldn't vacuum lock.

 

[Tchetek]

Be careful to disconnect the linkage between the throttle bodies and oil pump.

It’s easy to break the plastic clips.

I think I cranked that oil adjustment screw 3 turn up. But that was a while back.

 

[Teth-Air]

They were bad for cracking near the transfer ports. Look closely for that. Also they had a reputation of getting too little oil at lower rpms. Most guys cranked up the oiler 2 turns. Additionally you will notice that the oil tank cap is on an angle and the breather only opens when the ball inside strikes the breather valve arm. This would be naturally happening when the cap is perfectly horizontal and riding smooth trails you could experience a vacuum in the tank. Many guys would drill a small vent hole through the cap to avoid this. I also recommend testing the oil pump and brass nozzel while you have it out as this is usually due to lack of oil to that side. If you are unsure add 500 ml of oil to the tank on every fill.

 

[Modman]

I’m new to the snowmobile world but recently got a 13’ rmk 800 for cheap with a seized rod on one side of the crank. It has 1100 miles. I got a new crankshaft, fix kit and top end from Rev6 with all the gaskets. I plan on replacing the check valves and thermostat as well. I have some experience with 2stroke motors from dirt bikes and a jet ski. Just wanted to get some feed back on tips and things to look for while rebuilding it. I have read to turn the oil screw 2 1/2 turns to increase the ratio and that some people run 100:1 in the tank for extra lubrication after a bottom end rebuilt.
Any and all feed back is welcome as I have a lot to learn
Thank you

Call Indy Dan. He can press new parts together for your old one but probably has a crank ready to go. Get a wide bearing crank if they make one for that motor or a lighter crank (he also does drilling services etc). He's also got some stout parts for those Liberty's, like gusseted cylinders etc that will make that motor much stronger. https://www.indyspecialty.com/services

 

[K1Dbilly]

They were bad for cracking near the transfer ports. Look closely for that. Also they had a reputation of getting too little oil at lower rpms. Most guys cranked up the oiler 2 turns. Additionally you will notice that the oil tank cap is on an angle and the breather only opens when the ball inside strikes the breather valve arm. This would be naturally happening when the cap is perfectly horizontal and riding smooth trails you could experience a vacuum in the tank. Many guys would drill a small vent hole through the cap to avoid this. I also recommend testing the oil pump and brass nozzel while you have it out as this is usually due to lack of oil to that side. If you are unsure add 500 ml of oil to the tank on every fill.

Sorry to ask but what exactly is a transfer port and where will I look for cracking?

 

[K1Dbilly]

I'd just replace them, not worth messing around with.

One more item, check the oil tank cap and make sure it lets air into the tank, they've been know to plug and cause the oil pump to vacuum lock. Some guys used to use the smallest drill bit they could find to open a hole in them to guarantee they couldn't vacuum lock.

Is there an option to delete the oil pump entirely and just mixed your fuel?

 

[ABMax24]

Is there an option to delete the oil pump entirely and just mixed your fuel?

No. The only way the crank gets oil is from the oil pump. The fuel is injected into the rear transfer port and only lubricates the top end.

 

[K1Dbilly]

No. The only way the crank gets oil is from the oil pump. The fuel is injected into the rear transfer port and only lubricates the top end.

So unfortunately, I pulled the case apart and found this. Any possible way to fix lowercase or do I need to replace lowercase and will new/used lowercase match my stock top case?

 

[ABMax24]

So unfortunately, I pulled the case apart and found this. Any possible way to fix lowercase or do I need to replace lowercase and will new/used lowercase match my stock top case?

They can, and have been welded up successfully. That's what I'd do with it if it were mine, clean it up really well and tig weld that crack shut, remove the burrs from inside the cases and carry on.

Most people bolt the cases back together before welding, helps minimize distortion from the heat.

 

[Tchetek]

Put some JB weld on it and don’t tell anybody!

 

[Teth-Air]

Sorry to ask but what exactly is a transfer port and where will I look for cracking?

The slots that the air fuel moves up from the case. Check the material between the slots for hairline cracks. For deleting the oil injection it can be done but you do need oil in the pump area between the cylinders. A small tank with just circulation to it is acceptable. There is lots of info online about turning up the pump and is easy with the motor out. Also drill the small hole in your cap to breathe better.

 

[cattechsummitrider]

This isn't a Polaris cylinder but it gives you the idea,,,, Its a crack between any of the ports ,, They can be very small and hard to see

 

[JustinMan43]

One more item, check the oil tank cap and make sure it lets air into the tank, they've been know to plug and cause the oil pump to vacuum lock. Some guys used to use the smallest drill bit they could find to open a hole in them to guarantee they couldn't vacuum lock.

What I did was take a sewing needle or close pin and heat it up with a torch and poked it through the bottom. Nice clean and small hole. Couple of my buddies drilled theirs out and it would leak oil every time we rolled it over (which was a lot lol)

 

[K1Dbilly]

They can, and have been welded up successfully. That's what I'd do with it if it were mine, clean it up really well and tig weld that crack shut, remove the burrs from inside the cases and carry on.

Most people bolt the cases back together before welding, helps minimize distortion from the heat.

Ok so I found a good tig guy in town who said he’ll do it. What’s the best way to pull the oil/water gear shaft out? So obviously I want everything out of the case such as the check valves, the gear shaft for the water/oil pump and the two drains screws on the bottom. Correct?

 

[neilsleder]

Ok so I found a good tig guy in town who said he’ll do it. What’s the best way to pull the oil/water gear shaft out? So obviously I want everything out of the case such as the check valves, the gear shaft for the water/oil pump and the two drains screws on the bottom. Correct?

Yup don’t weld near those plugs with them threaded in. That those out. I personally wouldn’t worry about the other stuff in the block. Won’t get any hotter than the motor does while it’s running. I was going to off to weld it then seen you’re not very local to me lol.