[DannoXYZ]

What's history of this bike?
When was last time it ran perfectly?
What happened between then and now?

Most likely carbs are clogged and dirty. Given how easily and quickly it dies with throttle, best to do complete teardown and restoration. I've known many expert mechanics, who can rebuild engines with their teeth and hands tied behind their backs, have had to pull carbs 4-5x for ever deeper cleaning until it ran perfectly. I recommend doing complete job 1st time around.

Send to pro experts if you don't have experience or equipment (ultrasonic soaker, micro soda-blaster, etc.)

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[DannoXYZ]

Ran perfectly a month ago, then over a 2 week span it gradually lost power and then the next day I tried to start it and it does with throttle. Never had an issue with the bike before except a bad spark which was fixed with some new coils.

It very well could be a carb issue, but that wouldn't explain why the vacuum gauge was jumping around like crazy. I've taken carbs apart before on other bikes and outboard motors and managed to clean them just fine. I'm just hesitant because it's a pain in the ass on this one and I'm not 100% confident its a carb issue due to the vacuum guage

Where was this vacuum gauge connected?

 

[DannoXYZ]

Measure valve-clearances and adjust as necessary.

 

[DannoXYZ]

Yes, just have to remove radiator. Do valve-adjustment 1st, otherwise you'll have to do compression-test again after adjusting valves. It's not headgasket that causes the pulsing, it's larger cam-overlap from too-tight valve-clearances. You also risk frying valves when clearances are too tight, they don't have enough time touching seats to transfer heat away.