OS 46ax question
 

I have a brand new 46ax. When I try to turn the crankshaft, it feels like it is binding when the piston nears the top. I cant even turn the engine over. At least with no prop installed. I am a mechanic. There is no glow plug installed. It is not the smooth feel of being "bound" by compression. Is this normal?

RE: OS 46ax question
 

It is normal for these engines to feel that way, the cylinder is cone shaped a bit, they are designed that way. I always pull the glow plug, put a lot of after run oil in the carb and a few drops on top of the piston, turn it by hand a few times, then on a stand hit it with the starter while the plug is out for 30 seconds or so, then do my break in according to manufacture recommended procedure.This a huge part of why proper break in is a must with glow engines.

There should be a note in your manual about this very thing, I think on page 7.

RE: OS 46ax question
 

Mine did that too when it was new. It should turn over fine after you run it for the first time.

RE: OS 46ax question
 

I've had 1 46AX and two 55AX and all were exactly as you are describing. Conical shaped cylinder sleeve combined with the con rod being completely vertical at TDC makes it feel like it sort of locks in place for a bit.

RE: OS 46ax question
 

Yep, the "pinch" is normal. There is no piston ring on the engine so piston and cylinder clearances are a little different then on many other engines. The cylinder liner will actually straighten as it heats up I believe.

RE: OS 46ax question
 

Yep, Chuck brought up one of the terms you will hear out in the field, the pinch or squish. I have seen some brand new engines that squished so tight you had to heat the engine with a covering heat gun to get them to roll over. Did that then started the engine and it was fine from then on.