Need help with Scorpion 440

[monte44]

I am working on a scorpion Whip 440 cayuna that keeps burning down the PTO side. I am pretty sure its a lean condition causing this but it passed a leak down test. It has a walbro carb that seems to work decent. Carb was cleaned and rebuilt. Any ideas? Thanks.

[JD600]

Whats the history of the crankshaft? Has it been reciently rebuilt?

DE

[monte44]

That I'm not sure about. I'm guessing not. I took the project in because a friend of mine ( who has good mechanical ability) started it and gave up. I have not tore it apart yet. His dad bought the sled new and said that the pto side has always given him trouble. Just looking for a few ideas? Thanks.

[JD600]

A twisted crank would be my first guess on a singel carb engine that passes a seal test.

DE

[S_Kyle]

Try running a colder plug in the PTO side. My uncles had the same problems with there scorpions new, ended up using 2 different plugs. Did the same thing in my Whirlwind, nuked the PTO side.

[JDT]

This is a somewhat common issue with the Cuyuna's. Once you get beyond seals the next problem is heat buildup and that relates to air flow.

As mentioned a cooler plug on the PTO side will help.

The casting of the shroud and head in one can leave flaws and burrs in the fins. Plus the gap between heads leaves less air flow for the PTO side.
I always clean up the fins with a die grinder and file.

The performance of the fan is critical. Bearings, blades and the belt need to be in tip top condition.