I have a 1970 RT 1 that starts, run idle, but when I accelerate, it blubbers and quits. Have sonically cleaned all parts of the carb, still had the same issue. Help?

Sounds like o-ring that seals "jet setter" to float bowl is missing, damaged, or not sealing?

Blubber sounds like Rich, but shouldn't Quit. Best bet is to post a video if possible please. I shouldn't even guess at this stage & send you chasing things it isn't like [dare i say it--as i always do] blocked or very restricted exhaust. Or the carb small Oring that controls the main jet & if perished or shrunk it'll bypass the main jet & go super rich--but wouldn't stop, just not rev. As i said, i shouldn't guess just yet. On the other hand if you mean it fades out then 'that' sounds like a blocked main jet which you can access from the side of the bowl externally. Take the jet out of the holder as can get stuff behind it which gets sucked up against it as those jets flow back to front & you can't easily see whats behind it. #7 is the small Oring but go to the main jet first--easy to do.
www.partzilla.com/catalog/yamaha/motorcy...1971/rt1b/carburetor

sorry Mark i'm slow typing & thought i was first up haha. If ya not fast ya last.

We put a new O ring in yesterday. A Yamaha dealer/ restorer went thru the carb.
will try to make a video. Thanks for all your help.

Here is a crummy video of it running. There is a blacked out period where I restarted it…I was trying to hold my iPad…after the blackout, it comes back on with further issues. Jim

You need to upload video to Vimeo or YouTube and then post the link here.

Could be the condenser.
Take the flywheel cover of and have a look at the points as the bike is running.
You should be able to see a bit of sparking at the points, but if you see a lot, then I’d put my money on the condenser.