i have a 04 pro x 2 800 with 4700 miles on it. this past riding season i broke an exhaust valve , which fell into cylinder . ruined piston and cylinder. i made all repairs and updated to stainless exhaust valves , replaced bad cylinder and piston,honed other cylinder and new rings. so basically top of motor has been rebuilt. i hear alot about bottom end problems with the 800 motor and crankshaft issues. i have plenty of time in the off season (now) to do motor work.im just not too sure what should be done as far as far a crankshaft failure , which i hear can happen? is there anything i can do to prevent problems with crank and bottom end. as of now motor runs awesome. do i need to replace crank bearings? should i send out drive clutch for precision ballance? (i understand vibration causes crank problems) do anyone have any input to what i should do to prevent bottom end from failure like the top end did.? all help much appreciated. thanks..

Send crank out and have pto bearings replaced at a minimum. Have rest of bearings looked at.

As far as balancing the clutch, with 4700 miles on it it sounds like your clutch is balanced well allready., Replace the movable sheve bushing and cover bushing. Reshim the spider pucks and call it good.

Check inner sheeve for hairline cracks starting from shaft.

New h20 pump belt.

Check oil pump slot for elongation.

Take note on stator alignment and put it back in exact place.

Just like Alsled said-- At a bear minimum change the PTO bearings, as a matter of fact I would replace the MAG side bearings as long as the crank is pulled. I pulled my crank out of my 700 at 4000 miles, couldn't tell that there was any wear till ya pull the crank. Rebuild it now and you should have a trouble free riding season!! LET IT SNOW!!!!!

Had a friend who has the same sled and had the same thing happen at about the same mileage. Sent the crank out to SLP for inspection and tough boy kit. When it came back they had replaced all of the bearings, the pto end and the pto con rod. Apparently when the piston hit the valve, the sudden impact was so bad that it bent the connecting rod slightly. I would send the crank and cases to slp for inspection and the tough boy kit. If the cases are out of spec, then all of the other stuff won't matter, you will still loose the crank. Do this and what Al said and you'll be better than new.
Neil

Measure the crank run-out just to see where you're at.

thanks guys for all info. shortstop, do you know permissable run out specs on crank, in the 800 twin? i see that most responces say to send out crank and have bearings done,are replacing the bearings on the crank something i can do if i split the case and get parts from polaris or are special tools needed, for pressing bearings...etc.. i do not have a manual for motor, nor do i have any torque specs. does anybody have a link or know anywhere i can get an idea of what the job consists of before i get over my head? torque specs, assy procedure,etc? thanks again

alsled, thanks for info, i replaced water pump drive belt last year at 3500 miles , the slot and drive shaft for oil pump looked good ,permissable wear. cleaned out dirt and grime from inside mag cover. thanks for input.

I can't remember right now(as I'm slightly intoxicated) what the maximum crank run-out spec is.

4 thuosand