Re: Curious about the engine, :question:
That looks very similar to my first kit, Mine was running nice out of the box (only Fred head added before first startup) and I put about an hour and a half run time on it when I noticed my crank had a LOT of side to side play. I took it all the way apart to find a way to remedy this problem but in the process trued the crank, it was pretty bad, but they ture up nicely and easily. ordered new bearings, gaskets, and everything else I needed but wanted to work the case and crank better before reinstalling.
I bought a Dax bottom end to get the bike back on the road and this bottom end was way smoother running so I kept it in the bike. I did a LOT of porting and other fixes while waiting on the new bottom end, but also finished the other bottom end so it's ready to reassemble but I'm going to weld the crank and make a set of shims to get rid of that free play it has first.
For the good... the jug was very nice and had large ports to begin with, they're larger now but were nice stock.
The shorty intake, this one is one of the few that actually matches up to the intake port, most just have a small round hole at teh flange and not a lot of room to match port. only thing I did here was bore it out to 16mm because the stock 13mm hole on the intake manifold is restrictive and prevents higher rpm.
The piston and rings... nothing special here but they're nice and went back in the engine that I'm currently running.
Very cheap crank and clutch bearings... I'd recommend changing these before even running, one crank bearing was already noisy and rough after only 90 minutes of run time, and one of the clutch bearings was in even worse condition.
The crank was just plain sloppy... over .020" runout when first measured. I corrected it to nder .002" runout and the crank wheels had a ton of side to side wobble from being improperly assembled... I'm surprised it lasted 90 minutes... most likely what toasted the bearing and casused the side play.
I definitely make sure I know something about the engine and the seller before purchasing after seeing how sloppy this one was assembled, it had some good parts, but I'm thinking the lac of quality control on the assembly line and the cheap bearings are what would have killed this one on short order if I didn't give it that look over when I did.