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'77 GT80 running rich

3K views 2 replies 3 participants last post by  harrisonmark816 
#1 ·
I got both this and a Suziki RV90 in a trade. The RV90 runs like a top, the GT80 does not...

For the life of me, I cannot get this thing to run right. I have taken apart the carb and cleaned it several times, still can't figure out the problem. It fires up first kick, but runs incredibly rich, so rich that it can't get past about 1200rpm. It still has the stock jet (89) and the choke is not stuck open. With the choke in it's closed position, it completely seals off the pickup tube. If I shut off the petcock, it runs like a raped ape for about 5 seconds, until it runs itself out of gas. It smokes A LOT, but again, from running so rich. It has a working oil pump, so I thought that maybe it was oiling too much. Nope, does the same thing on a 40:1 premix with Yamalube 2T.

I have googled myself to death trying to find someone that has had (and fixed) a similar problem, but have come up empty. These things are, apparently, rare as shit. I'm almost to the point of buying another carb, just to see if it fixes anything, but they're like $90 on ebay, and I don't really feel like dumping that much cash on something I'll probably only ride around when I'm drunk.

Another thing, does anyone know if any if some of the parts are cross compatible with any other Yamaha models? It needs a new ignition, key broke off in the existing one. It broke off in the on position, which is good, I guess, but I would still like to replace it with a working unit.

Thanks to whoever may be able to help me out on this. I don't really want to part it out, it's in near mint condition, would be a shame.
 
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#2 ·
Did you disconnect the oil pump while running the premix? if you did and its still smokes with 40/1 you need rings or a bore job. that bike also has points so i would make sure gap is right and buy a hotter spark plug first. If it still smokes after that the oil ring is probably warn
 
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