Just picked up a Tri Moto 225 dx 1985...

This thing is sweet! I took it for a ride but it had a knock in the engine. It actually sheard the keyway, so I took the motor out by taking the back end off because it is shaft driven did not know if there is an easier way? I have the moto out tood the head off and it is very clean as well as the piston moving very nice. I am not sure why it had a wicked knock in it? I am trying to split the case and had all the screws out is there anything else I need to do or how do I split the case I am unable to do so?

Anything else I need to know, I ran this thing around the yard one and it had a ton of power just trying to figure out the knock I thought it would be a little more noticable for how loud and being s sheared the keyway but it is very smooth? any help would be great!
Thank you!

 

i think it might be the rockers
you should take the side covers off the head there should be a ajustment screw that what it was on my moto 4 225 and there the same motors.

 

make sure the rod isnt worn, it should have any up and down play but should have a lil bit of side to side play, also check timing chain,rockers, valves.