"New" to me 87 VN750, my first bike and first carbed engine but I'm a very fast learner. Wouldn't idle, rich, stumbling, and the prev. owner said it died on him by the time he got to 3rd gear.
Wouldn't idle at ALL when I tried it, hard to start. Got it home & the idle was set really low. Had to turn it up almost all the way to get 1100 and it fires right up now. Idled rough & rich for < 5 min and died. Set it up to 1300 to keep it running until I fix the AFR problem. I'm guessing I'll have to set it back down once I fix the AFR.
Still pig rich both at idle and revving. Pulled petcock vac & got 1 or 2 drips of fuel. Reconnected, ran for a few min, nothing in the line now so that looks ok to me?
Doesn't look like anyone has ever monkeyed with the idle screws. Anything to check before I go through the hassle of pulling the carbs?
My guess is unless its been rejetted...you might have some float bowl valves that aren't closing...letting the bowls overflow and flood the motor. Could also be a clog somewhere else in the carb....either way you'll need to yank them and clean them.
Could also be stuck chokes. (Which are just circuits that toss in more fuel)
I checked the petcock as best I know how. It seems to operate normally by applying vacuum, and there's no fuel coming into the vac line that operates the petcock.
I blew out the carbs backward so I'll see if that made any difference. Otherwise I'm just pulling them for a real cleaning and rebuild if they need it. If they're dirty enough to run this badly I may as well clean them right.
Yeah at first there was one drop, maybe two. I'm really not sure how they got there, but it doesn't seem to be drawing any through the hose. At least not enough to make it run any differently. I ran it again just now with a big looping hose on the vac line to catch gas in it, but nothing. Dry.
Time to pull the carbs for a deep cleaning and maybe rebuild unless there are any other ideas.
You should be able to run the motor on just what is in the fuel bowls, no vacuum line hooked up. Might try that. Long shot, but there should never be fuel in that line ever.
An unknown history carbed bike, and then add that it is 26 years old, a carb cleaning is obviously mandatory! Clean it and then start troubleshooting if needed.
There's some gummy stuff where the air baffles are clamped. Maybe some kind of RTV? Otherwise everything looks to be in good shape and pretty clean. Nothing looks worn out, broken or sticking. Guess I'll try to get these #*$& carbs back in and see what how it runs.
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