Motor advice?

[Ghuds]

Took the sled out for the first time last week. Ran great, towards the end of the day started to get a little noise from the motor. Same noise I got from my old sled when the PTO side cylinder went bad. The noise sems to be the rod rattling on the crank when there is too much slop in the cylinder / piston. On my old sled after I did the top end the noise stopped.

I tore down the top end on the new sled and the cylinders look great and the pistons look pretty good (no major scoring, cracking or missing pieces).There was however, too much play in the rings, making the pistons loose in the bore.

All this to say, I was wondering how much play should there be in the rod bearings? Don't know if I should just do the top end or if I need to do he bottom also.

2002 800RMK Vertical Edge 156

 

[knifedge]

These engines are known to need crankshafts at 1000 - 2000 miles. Pull the engine, take it apart, and see what is up before you ever start the engine again.

--You can get a crankshaft rebuilt from Northern Crankshaft

http://northerncrankshaft.com/

 

[Ghuds]

Forgot to mention, before I tore it down it had a little under 110 p.s.i. compression in each cylinder.

 

[sno*jet]

imo the crank reputation was a little over-done on the internet. I ran an 02 for thousnds of miles, ruined pistons, re-built with wiseco and kept going. having a good dealer service the clutch properly is key imo. they should also be able to measure the play if any in the crank and tell you if its questionable, before you do a complete teardown and open that box up..
have you checked out the water pump assembly yet?

 

[Ghuds]

I bought this sled from a kid who got it from his uncle when he passed away. The kid told me that his uncle had the entire motor rebuilt at around 2000 miles (it has around 3000 now). He wasn't able to get any paperwork on it though. The motor was running real well, even with the noise which I believe is coming from the play in the rods due to worn rings / pistons.

I just had to replace the recoil rope so I checked the water pump and belt and everything looked fine. When I checked the ring gap it was about double the max allowable according to the manual. The wrist pin bearings seemed real loose as well so I ordered new pistons, pins, rings, wrist pin bearings and gaskets. My thought is to do the top end and see if it quiets down. If so, I'll ride it the rest of the season and do the bottom end this summer. If not, I guess I'll bite the bullet and do the bottom end now. I only paid $1500 for the sled and put a seat cover, bar rises and cables on it for another $350. I figure if I have to drop another $800 into the motor I'm not in over my head.

 

[Goinboardin]

Could this be noise of piston slap? As in too much piston to cylinder wall clearance?

If it really were due to bad rod bearings it will lock up very soon. Too large of piston ring gap will have no effect on rod bearings. Seems you may have some engine terms a little confused?

 

[Ghuds]

Seems to me that if the piston is wiggling around in the bore it will increase rod bearing wear. If the pistons were tight then everything will be tight - correct? Also, the pistons and bore are still within factory tolerances. That's why I'm in need of advice.

 

[whoisthatguy]

110 psi compression means the rings were shot. Good rings are 145 psi. Somebody either abused the engine or it was never rebuilt.

 

[Ghuds]

Exactly what I was thinking. Should have the parts by the weekend - we'll see what happens!