372XP issues, no start

[slambox28]

Hi, I have a 372xp that won't start or fire. It seems to have high pulling resistance after it quit mid cut. It quit on me when sawing just one cut on a 2x12 cedar rough cut lumber. It seemed to abruptly lock up on me but it did not sieze and the piston to the cylinder..
Here's the circumstances; been sitting quite awhile in a horse barn, older mixed fuel used and a hint of oil added and shook up, polaris 2 stroke oil. Started up and didn't run like normal, lots of throttle lag, engine bogging down on the slightest cut. Ran it at higher rpms only for momentum to cut then it bogs down right away. After it quit now it wont fire even after hot now and it has what's believed to be much higher pull resistance now.

Here's what's been tested:
-new cylinder and piston, still the exact same very high pull resistance
-new crank bearings, new piston rings, still no changes it wont fire
-splash of fuel into the carb no fire at all
-spark is tested and known good new plug
-crank is centered
-piston rod bearing is definitely ok

Remaining possibilities:
-crank seal got pressed in to far on the pull handle side?
-crank bearing got ruined on install from a propane torch?
-crankshaft is somehow bent?
It has brand new fuel now at 40- 45:1 ratio and won't start at all it wont even fire, I really don't know

 

[Bob Hedgecutter]

Start removing stuff and testing rotation until it comes good after removing something.
If you have everything removed and the resistance is still there- I would suggest severe side loading on the main bearings- if indeed the big end bearing is still 100% fine.
Were the main bearings toast so you replaced them? If a saw stops and locks up it usually means something metallic is flating around inside the engine- most often this is a piece of bearing cage.
How about some photos of the old piston and cylinder?

 

[slambox28]

Sure, it seemed to lock up, but it just quit abruptly when cutting and still can turn over afterwards.
The bearings seemed to be in very good shape at first but after fine testing I could notice a slight gritty feeling and when turning the inner race back and forth with a finger it seemed brand new but when full rotations in the same direction it would stop every 2-3 turns of the inner race while still in the case. It has new SKF bearings now.

The old cylinder is pretty shiny in the piston range but the piston has no slop so I reused both with new Caber rings. Another reason for this is when I tried a brand new cylinder kit it had no changes either.. so wanted to continue using the old one and keep the new on standby.

 

[Bob Hedgecutter]

Cant really see a whole lot in that photo= but it looks like nothing has been on top of the piston and smashing into the squish band as often happens if something metal makes it through the transfers and ends up on top of the piston.
Edges of the port shown in the photos look pretty rough though.

 

[slambox28]

Ahh that's something I didn't notice. When replacing the cylinder, it didn't seem to help anything. I can swap the new cylinder on it now and see if it will start.