Can you spin it up with a good drill to save energy trying to start.
I've done that on my 100cc initialy just to get some response & it worked a treat.
Actualy very much like an LT2 "LS3" road version of LT2.
Just be sure the throttle is closing fully & flywheel nut is tight so crank key won't be damaged.
I have a video somewhere--more for a laugh but shows it works & no effort while you're experimenting to find the problem.
That bike was an absolute rocket but the LS3 has a better ported cylinder where LT2 is for trail riding.

Just looking at this i see i grab the flywheel at the endas it kept sort of seizing--binding up i called it because no damage but ran for only a few seconds & was caused by carbon blowby build up all the way down the skirt--hard to imagine' i know. Freed up in 10 seconds to do the same many times untill i lifted the cylinder & found 'that' Clean up but 'no new rings' had full comp & ran like a champ. Might've been when i got it running on petrol it ran for only a matter of seconds then bound up solid for say 10 seconds then would free to re-start & a totaly silent motor--as no piston clearance at all haha. Anyway--spin with the drill trick--anticlockwise as you look at it.