I'm rebuilding a MC21 rolling chassis I had back up and have installed a rebuilt engine I purchased. It came with no kick starter but I had one so that wasnt an issue. THe issue is that when i kick it over its very stiff and will not return unless it is pusshed up. Pulled the engine cover and it seemed fine and would return freely so I figured the oil seal which was looking rather used was at fault so I replaced that. Same issue, tho with the engine cover bolts loose it will return. TIghten them up and it sticks. Any suggestions on what to do next would be appreciated.

cheers,