I had a real hard time with a gt250A once upon a time(s)
Was it a running bike before you did project?
Post a video of it running!
How hard is it to stick the points back on?
Micron wrote:Crank was reconned by Chris Applebee
What was done exactly?
I don't think 20 degrees vs 24 degrees is enough of a difference to cause what you describe, but should sort that out.
If you don't have dial gauge, but have Vernier Calibers with a tail, you can extend the tail into cylinder to do measurement
I have timed many bikes via Rotor marks and no mechanical problem all very accurate. Unless key way or crank spun
Since the crank was torn down it would be good to verify back together OK and checking rotor timing mark to actual piston/crank position with gauge in cylinder will sort that out. And, if you find rotor timing marks are off significantly something else is wrong in my experience
swap carbs (even if left and right carbs I think can be rigged for testing?)
Is the top end noisy? Rattling more than it should.
Can you shake either end of crankshaft (bad bearing)
If the crank is off, it quickly makes piston wears the cast iron liner. Take off exhaust, raise pistons to see if liner has lost all it hone marks. I think intake side takes it the worst, bit check both
What else
Oh, With carbs off. place you hand over each intake and kick it over. You should feel sharp suction and both equal.
Is transmission binding, Disengage clutch to test maybe?
Kick it over by hand short quick moves as piston is up stroke compressing, If good piston/ring fit it should feel smooth and bouncy/ springy. no air leaking past rings... no binding. Use kicker by hand get a good feel as you try each piston
good timing, Sharp long blue spark arc
Carb (check float height with hose level) Mikuni Jets all. Stock Airbox
Oh what was wrong with my Gt250A. First time too much fuel due to me trying to do airbox swap. Starting new jetting choices rich on an oil injection only system is not safe as they say... fuel washes oil away... mix a little oil in tank if you are doing a complete new carb intake setup
another time crank shaft Rod/big end out off spec (after about just a few hundred miles of use) causing piston to slam against cylinder liner intake side. Piston really no wear, but liner wore out. Top end noisy (Yes air cooled two strokes are, but should not be that loud)
Not sure if this helps at all, but it brings back some awful memories.
Good new is once you sort things out... It is a freaking little rev rocket with no torque below 4K RPM. I couldn't drive mine slow