Losing spark with throttle. '80 250T

[Guest]

I finally got good spark, but the motor still bogs when the throttle is opened. It starts fantastically now, and jumps right up to rpm. A few seconds on the choke and it idles beautifully.

I have one of the little Lisle spark testers, where you just lay it along the wire. It shows the spark dropping off at precisely the same time the engine bogs and sputters. Like the spark is blowing out. If I let it continue, the exhaust begins to burn my eyes, suggesting very rich/ unburned fuel.

I have cleaned all connections.
I have done the coil relay.
I have replaced the plugs, caps and wires.
My battery is well charged.
Carbs have been cleaned about 40,00000000 times in the last month. New o-rings and carb boots.
Air screws are currently at 3 turns.
Valves are done.
Compression is 147 and 153

What am I missing??

thanks!

[tom203]

Can you "nurse" the throttle and get this thing to run sorta smoothly at 4000 rpm? Can you determine if just one cylinder is not firing?

[MatBirch]

I can, but it isn't real smooth. Both sides lose spark. I opened the gap up a bit and it helped , but still struggles off idle.

[tom203]

Have you checked the charging voltage up to moment when it loses spark? Maybe the voltage is falling off as it revs giving the ignitor fits.

[MatBirch]

Have you checked the charging voltage up to moment when it loses spark? Maybe the voltage is falling off as it revs giving the ignitor fits.

Alright, alright... Back to the stator papers... Across the battery I only get about 12.4v at 4000 rpm. (Have to have the choke on to get it there, but I'll get to that later...

thanks, I'll be back