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hello!
trying to figure out what is wrong with my 1986 Vulcan 750. bike starts fine, idles fine.. i shift through 1st, 2nd and 3rd just fine. when i shift into 4th and 5th gear and start crusing with a steady throttle there is a hesitation and the bike surges. it will slow down and speed up with a constant throttle. if i really give it some throttle it seems to accelerate ok with maybe a bit of "surging" but its bad when trying to hold constant speed.
saturday i changed the oil and the final drive oil. i also added some seafoam to the tank.
any ideas as to what coudl be causing this? thanks!

how are your plugs?

not sure how the plugs are but i know they were all just replaced a couple weeks ago by a family friend.

sorry but i am a total newb, what does one look for when checking the plugs? i hear of plugs being "fouled" but i really don't know what that means.

i didn't have a weird start the other day. i have a slight problem where gas will leak out of a carb occasionally. then i try to start the bike and it won't start until i lean the bike around and stuff. then i tried to start it and it backfired out of the right side of teh bike by my leg. then it started fine after that. but it was after that when it started acting wierd and surging. so maybe that ruined a plug?

i've also read about some sort of needle or float in the carb possibly causing something like my problem. but like i said, the surging only happens at about 40mph and higher.

when they say plugs are "fouled" it just means that they are so covered in carbon from poor combustion that they don't fire as well

depending on how much you tipped the bike when you were trying to start it you might have gotten oil up on the plugs, but you would have to tip it pretty far for that to happen

as for the float/needle pins and or jets being clogged, i don't think that is very likely because you say it runs well until you get up to 40 mph

the surging makes be think that possibly your throttle slides are messed up but that's a pretty far guess

how does the bike respond when you give it gas? is there any lag?
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ak47 seeds

nachos4life wrote:hello!
trying to figure out what is wrong with my 1986 Vulcan 750. bike starts fine, idles fine.. i shift through 1st, 2nd and 3rd just fine. when i shift into 4th and 5th gear and start crusing with a steady throttle there is a hesitation and the bike surges. it will slow down and speed up with a constant throttle. if i really give it some throttle it seems to accelerate ok with maybe a bit of "surging" but its bad when trying to hold constant speed.
saturday i changed the oil and the final drive oil. i also added some seafoam to the tank.
any ideas as to what coudl be causing this? thanks!

Sounds like it is running lean. Try running the carbs a little richer as this should clear up the surging at a cruising speed.

well today i took it out and it ran fine? i am not gonna say it fixed itself yet. i'll see how it does on the way to work tomorrow.

i dont have a tool to pull the plugs. my crappy spark plug socket wont fit.

when it was happening, throttle response was good and normal it seemed until i got going around 40mph or 50 mph in 4th or 5th gear, then there would be a slight lag occasionally.

i was reading something about throttle slides.. hmmm.

and i will try to run the carbs richer. i think i know how to do that.

i am having the exact same prob with my 89 ninja 600 and my 92 suzuki katana 1100..my plugs are fouled.."black sout" meaning im rich or not enough fire...i checked my fire it is fine adjusted the carbs they are fine would a vaccume leak cause this.....oh i also changed to a hotter plug..