rimigo

Easy, take the exhaust of (when it is cold ). Lift the head of and lift the barrel of.

You can now inspect the ports in the side of the cylinder wall and see if you are right. As it is a 2 stroke there is nothing to be worried about with regards to valves and timing.

You will need new gaskets though and be careful with the piston and the rings.

Have you removed the coke from the exhaust? This could also impede running.

If the exhaust is very coked up, you need to look at what mixture you are running as it could be too oily.

With the barrel off you can also check the problem isn't further down the line...Main bearings, or some problem in the clutch/gearbox...maybe no oil?

Stripping down 2strokes oh happy days...

You remember cleaning out the exhausts?

Loads of petrol down the thing and WHOOOF! Oh happy days indeed

Could be that the ring gooves have got gummed/coked up...the rings should be free to slide around in their grooves. It's tricky to get the rings off, and the ideal tool for cleaning out the grooves is an old broken ring . Still a new set of rings isn't too expensive.

Heck we'll all come round and play if you buy the beers!

Del

Have you given these shop's permission to open the cylinder?

A clogged exhaust port will not make a two stroke hard to turn (but will reduce power output). A seriously carboned head will raise the compression ratio, but it would not usually be perceived as "hard to turn" -- a 50cc anything is easy to turn over with a kick starter lever. Decarboning the head and exhaust port are standard maintenance, so pulling the head will tell you a lot. If it is really hard to turn, I'd suspect a partial seizure, which has left the cylinder badly scuffed.

I think Ken has it right

seized, someone accidentially forgot to premix.

One odd thing that a "piston port" 2 stroke engine (many small two stroke engines are) will do is feel like it is locked up because fuel in liquid form has accumulated below the piston.

The fuel/air charge is pulled into the crank area before it is forced thru the transfer ports in route to above the piston. If the engine sits with a slight fuel leak, liquid fuel accumulates in the crank area and the "below piston" compression goes way up.

If the shops had the engine apart this excess fuel would have already been cleaned out. If it has not been apart, take off the carburetor and the reed valve (if that is the set up) and carefully rotate the engine to get out excess fuel.