Compression and timing question.

[Chicken Sandwich]

i have an American powersports Blue Thunder with a Hammerhead 150cc. It has the internal F/N/R transmission so I’m not sure what GY6 engine version it is. None of the part numbers match to the ones on the internet but i did find GY6 stamped on the case upon disassembly. I made a post earlier about it. I got the go cart with the head and jug off and the something tore up the piston and head. The cylinder looked ok. The previous owner blamed the CDI box and advanced the timing to the point it blew up. Not sure if the story is true but i bought an upper rebuild kit hoping it would work with my model. I couldn’t get the “T” mark to line up with the cam hashes level. If the cam is level the crank is between the T and F. So i just set the piston at TDC visually with the cam level. Ran the motor with a drill till i had oil to the head and checked compression. 180 psi. Just not sure why it wont line up and it the spark timing is set. Previous head and piston in the picture. Note the engine stand. I took the swivel off a boat seat and screwed the wood to it so it rotates lol.

 

[Whitetrashrocker]

Probably need to jump a tooth on the timing chain.

 

[Chicken Sandwich]

Tried that a tooth forward and back and with the tensioner in place. It’s really about a half a tooth off. The first 2 are when the crank is set and the last T are when the cam is set.

 

[Whitetrashrocker]

Has the key sheared or an offset key been put in?

That piston and head look like something went round and round in there.

 

[Chicken Sandwich]

The key looked fine. I didn’t know they made offset keys but it did look centered. I thought the same about the key and double checked it. About the piston tho. The previous owner blamed the CDI box but when i got it home i noticed he heli coiled the spark plug hole. And it’s really off center and at a steep angle. So steep you can’t put a socket because of the clearance. I think he tried to repair the thread and the electrode from the spark plug hit the piston. Since the cylinder looks ok i assume it happened on start up and he shut it down. There was a piece of metal imbedded in the piston so i pulled it out and it was magnetic. So it narrows it down to steel. When i split the case I didn’t see a debris and the oil was pretty clean aside from some disco party so I don’t think it ran long. I did find a video where the guy explained he put 2 gaskets at the base of the jug because he said he’s seen the the piston too close to the head. Especially with thin overseas gaskets.(Which is what i bought) so i may try that to see it it will rotate the crank if the deck height is higher. But i still need a carb, CDI box, ignition switch to even see how it runs and if the spark timing is off. I do have a timing light. Can you adjust the timing by sliding the pickup?