View Full Version : 1990 vulcan 88 carb problem

06-19-2016, 3:10 AM
a couple weeks ago i bought a 1990 vulcan 88 and it keeps flooding the engine. the guy i bought it from said it was rejetted one step above stock. I've already torn down the carbs twice and adjusted the floats. it will start and run for a few seconds and floods again. any help on the subject would be greatly appreciated.

06-19-2016, 1:33 PM
Leak check your carbs OFF the motorcycle using a dummy tank (old riding mower tank or whatever so long as it is CLEAN inside). Outdoors is best.

When you leak check carbs off the bike you can do things like removing the float bowl and operating the float with your finger to verify needle and seat are doing their jobs. I support carbs with whatever is handy so they stay in stock operating position. If they don't piss immediately I leave 'em a while and come back later.

Take a CLOSE look at needles and seats under BRIGHT light and with a magnifying glass if needed. The Viton tips on needles should be black, smooth and not have an indented "ring" around the. When it doubt, replace the needle. The seat should likewise be smooth where the tip contacts.

I love these valves for dummy tank use, on mowers with that fucktarded carb solenoid setup in the bowl, and any where I need to shut off fuel. I buy 'em by the bag off Ebay. Some people use them on motorcycles as inline shutoffs if their petcock is fucked. They certainly work but may be restrictive for some engines. Example below:


Carb problems are the most common hassle on old motorcycles with electrical shit running a close second. Once you figure out the basics you can work on any of 'em, and one of those basics is leak checks.

06-20-2016, 11:26 PM
thanks for the reply farmall!

this thing has me puzzled. it will not run at all with the fuel pump. i can start it up with the fuel shut off and as soon as i crack open that fuel valve the engine shuts off immediately and floods. i decided to try running a gravity feed and it starts up and runs. not extremely well since the carbs need adjusted but it stays running. i should say it don't idle well but it revs up no problem. I'm thinking the bigger jets are a problem. i don't think it needed re jetted, it has a custom 2 into 1 straight pipe on it, not like it has 2 wide open pipes. I'm not sure what for jets the guy put in but it seems like it's dumping fuel. i haven't had the time to really try tuning it since. any suggestions? should i keep the jets that are in it or go back to factory?

06-21-2016, 6:13 AM
You should fix your flooding problem before you attempt to tune.

06-21-2016, 6:18 AM
Flooding can be caused by misadjusted floats, sunk floats, bad float needles/seats, dirt/debris in the line(s), over pressure from tank (tank vent or regulator), needle seat o rings, etc.

06-21-2016, 6:21 AM
Simply being out if tune is something else entirely.
If your running rich, and the dude said he re-jetted to match the pipes, let's first assume he did and check around that.
Rich conditions can be caused by...

07-17-2016, 5:12 PM
sorry i haven't responded for a while, I've been screwing around with the carbs. looks like I'm gonna replace the floats and needles just to be safe. i also put the factory jets back in but when i do the floats and needles i might try those other jets again. also I'm having some new issues, the clutch is slipping. i don't think it should be shot at 22k, I'm thinking the master cylinder is bad. i decided to change the clutch fluid and cannot get any pressure built up in the lever. i had removed the banjo bolt from the master cylinder and there was no fluid coming out of it even when i squeezed the lever. so i put my finger over it and squeezed the lever and got some suction and it started squirting so i put the banjo bolt back in and it built up pressure. after that i bled it multiple times and couldn't get it to build pressure again. any thoughts?

07-17-2016, 5:44 PM
Return hole is probably clogged. Drill it out oversized. Carefull not to cut the seal(s). Should still be smaller than the feed hole.

07-17-2016, 6:12 PM
thanks sky i will try that