Definitely get it to a dyno, even if it's only for a print-out. We can then have a look at it and try to help.

I'd start by dismantling and cleaning the carbs properly, then ensure the correct jetting is there, as well as the mixture screw setting.

Honda's in general don't seem to like old fuel in the carbs, and whenever I've left mine standing, I always drain the float bowls off before trying to start it. Saves a lot of sweat!

Have you checked the coil contacts? As on another current thread, they can open up and cause pitting. This will reduce the voltage available, making the spark weaker.

Once you've done that lot, get back to us!
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