12' Pro rmk problem.

[prormk12]

Hello. I went out for a ride with my pro rmk 800 last weekend, when suddenly my engine stopped, and engine was stuck. Ive been driven for about 30 minutes, så the engine was nice and hot(125 degree). Got a friend to come and tow me home, and opened the cylinderhead. On PTO side it was quite thick gray layer of grease on the top, and also a little in crankcase. piston did not look good on the intake side, and cylinder was all scuffed up.. seems like coolant?
So now it needs replating, but I cannot find any cracks anywhere, and cant see any broken gaskets... anyone got any idea?

 

[The Bob]

Injectors? I would send them out and have them tested and cleaned.

 

[prormk12]

Ive got another pair of injectors, will swap em

 

[tek9tim]

Speaking in generalities, intake side damage is typically due to something getting sucked into the engine. Now, the Polaris piston design shortcomings (real or perceived) could factor in and cause this kind of failure without a foreign object making its way into the crankcase.

The gray goo you see is finely ground aluminium from the piston. To me, it seems like that piston just continued to be run for a bit after the damage occurred. That's about all the goo can tell you, unless you can confirm that the liquid base in it is in fact coolant. But, if the piston was forced up and down after the ring seal was compromised by whatever caused the damage, the fuel and oil would continue to be dumped into the cylinder, but there would not be sufficient compression to burn it. My money is on oil being the liquid part of the goo, with the fuel having since then evaporated.

I know, not any help. But typically speaking, excess heat issues such as those related to fuel delivery problems show up on the exhaust side of the piston.

 

[prormk12]

Wow. That was an really helpful answer! But Its a little strange that the sled ran just fine right before that. Could have been just a small damage that made this gray goo? Well, i dont know. Next thing will be new wossner pistons, replated cylinders, top end gaskets, new crank bearings and seal, fresh fuel, and new injectors.. hope this will solve the problem

 

[Reg2view]

I'd also be looking really close at crank and rod bearings, and any marks on the case. Like a PTO rod bearing starting to go and rubbing. How do the crank bearings roll? Did you notice the motor going soft before it locked up (loss of port timing)? Without fuel in the case, only oil, things will look different.

 

[Mountainhill]

am i the only one who does not like the ves gold oil? (dont know if that's run here)

all the engines i've seen running poo oil has a lot of carbon deposit buildup on spark plugs, pistonheads and exhaust valves!
have heard of cases when chunks of such deposits come loose and destroys pistons!

we run racing oil, leaving nothing but oil film, soot and a gooey black mess in the exh. valve that looks and feels like grease! no chunks of hard carbon!