I have an OFNA Picco .12 engine, and I have run about half a gallon of fuel in it so far. Break in was smooth, and I still preheat the engine as there is still significant pinch before start-up. However, after running about 4-5 tanks of fuel, the flywheel locks and does not turn, even after I again heat the engine to close to 200 degrees.

The last time I ran it, the engine got stuck and still refuses to turn over, even after heating it. Could this be a problem with the connecting rod, the crankshaft, or something else?

Thanks!

Try opening the motor and check.

caster oil in the fuel may have gummed the engine up on you when you heated it up...I have seen it happen several times now...take the engine apart and see

With new pistons it is common there is some expansion after heating up and cooling down, this proces will stop at a certain level.

maybe you bent a rod?

I opened the engine and saw that it's gummed up pretty bad, so I'm going to try soaking it in mineral spirits for a while.

Is it normal for the piston to be caught at TDC while idling after running? When I see that there is almost no fuel left, I usually just let it idle until it stalls and then put it on the starter box with the glow plug to burn off excess fuel, but I couldn't do it last time.

It wont run correctly if there is a bent conrod

I have Sonic .12, its Picco base. This is my first Picco engine. I've found the pinch zone for this engine is larger than Nova. When u check the sleeve, u can easily see 3 different zones. It shd be visible 2 zones when the break-in is done. Of course gumm is built-up because it still running rich on 25% fuel, when temp goes up, the gumm will gone.

I graduately lean the HSN and keep running it, consumed around 1L break-in fuel and 1.2L 25% fuel, its still slightly caught on the pinch zone. So keep some temperature and pay some for time for it.