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starts for about a second then dies

11K views 29 replies 7 participants last post by  romeobravo172 
#1 ·
Hi, new to the forum but have been reading it for about a week or so since i got my Vulcan 750. its a 97 and has about 25000 miles on it. i had made the deal over the internet as a trade and the guy told me that it just needed front brakes and it was having a problem idling. It turns out he had another Vulcan, and was robbing parts off mine before i got there. i got most of the parts, never seeing a Vulcan up close put me at a dis advantage (didn't now what i was looking for to be missing). i did get most of the correct cosmetic parts except for the chrome piece that goes on the right side and appears to screw into the right rear cylinder. i saw the holes but didn't think anything about them, and a friend was out last night helping me diagnose the not starting problem and said that air blew in his face when i was trying to start, so i found two screws that would fit into the holes and plugged em up, but i cant verify it blowing as i never felt it...

I have it all together, did a bunch of preliminary cleaning of the gas tank, and petcock, those are functioning correctly. It seems to be getting gas.

here's what it does, i'll go out there and it's cold, i put it on full choke and it starts for about one or two full rotations, then dies and won't fire back over, but sometimes acts like it wants to. I've tried no choke and 1/4, 1/2, 3/4 and full throttle, and it did one time run a good rev, and then die, but that was last night. i was freaking out because it wouldn't start and stay running then i noticed the oil sight glass had no oil in it :doh: so i stopped everything thinking maybe it was just pulling all the oil into the engine off the oil safety, and killing it. I added 3 quarts of oil today :doh: and tried again this time more confident i wasn't doing permanent damage to the engine. i got it doing the same thing and would run the battery down trying to get it going, i've spayed a bunch of b12 into the carbs hoping to maybe knock out some goo.
waited til the battery charged and tried it again, i managed to get a couple good and loud back fires, and it started for about 3 seconds (woot) but then died again, and repeated all above.

i've tried turning the idle knob at different settings and cant seem to get this bad boy to fire off and stay running. any ideas? i'm really hoping not to have to pull those carbs, they look like more fun than a barrel of rusty monkeys, to remove.
 
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#2 ·
Put the bike on the centerstand with the engine not running. The oil level in the sight glass should be almost to the top of the glass, not over it. If you can't see a bubble, drain some out. If you needed three quarts of oil, it was way low. When the engine is running, you won't see oil in the sight glass. If you do, there's too much oil in it.

Your battery may be weak. You can jump it from a car battery but do not have the car engine running.

Pull the plugs and see what they look like. May be time for new ones, and many here favor the iridium plugs. http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html

The carbs may need cleaning too.

Where are you in Arkansas?
 
#3 ·
i added the oil and wouldn't dream of putting a bike back together without putting it on it's center stand (if it has one). I love the sight glass, had too many small bikes that didn't have one. Of all the bikes i've sat on in the past month, to me this bike felt the best, sets up easy, feels very balanced and didn't seem to wallow when the wifey was on the back, so i was lucky to get the trade.

So you think i should just suck it up and remove the carbs? i've been dreading it.. is there another way?
 
#6 ·
So you think i should just suck it up and remove the carbs? i've been dreading it.. is there another way?


I'd try filling the carbs with SeaFoam and letting them sit overnight, then spray down the fuel nipples with Gumout letting the bowls drain.

I'd also make sure the gas is fresh and let some run through a screen before connecting back to the carbs to make sure there's no crap going into the carbs.

If it runs for a few seconds and dies... it's usually a clogged jet.

Are the air filters OK?
 
#7 ·
i've added fresh gas, after i cleaned the tank a bit, i'm curious as to which hose is the vacuum, there's two i'm not sure about their function now that a vacuum is mentioned, the one one the back of the tank i assumed is a vent, which i cleaned out just a few minutes ago and had a small amount of fuel in, and the one in the middle of the petcock, i'm gonna go see if it's clogged as soon as i get away from the comp. I thought about one of the jets being clogged, but if i tried to start it at say 1/4 or 1/2 throttle wouldn't that bypass the primary jets? oh yeah the answer to an earlier question, i live in hot springs, ar
 
#8 ·
The middle one on the petcock is the vacuum line.

You're not as close as I hoped, but very near some good riding!
 
#10 ·
Bill--pulling carbs is a night mare!!! Try Knife's way first, get some sea-foam and fill carbs and let sit overnight and flush with fresh gas till nothing but clean fuel comes out. This may or may not cure your gummy carb prob but sure beats removing them if you don't have to. Chance is your pet cock is gumed up also, easy to get off and if you are real careful can dis-assemble and re-assemble without new parts-- By the way you will get the best advice here! RB
 
#11 ·
i'm gonna go ahead and vent for a moment, and appologize to the japanese about hiroshima... also i have to remove the carbs because someone put them on backwards, the r was facing the front of the bike and the f pointing torwards the rear!!! i don't think it's supposed to be that way... if i'm wrong, i'll check back before i reinstall them and please correct me!!
 
#12 ·
From what ive read, you have gotten a lot of good advice. Since your new to the 750 here is something to keep in mind.
This bike needs a good charged battery to turn the engine over and power the ignition, it can get really hard/impossible to start when the battery gets a bit low.
Another thing I would check after you get it running is to make sure the charging system is putting out the correct voltage, should be 14-15 VDC at the battery terminals with the RPMS up a bit, say 3000.
Hope you get your bike running.
 
#13 ·
Bill, the carb marked F is the rear cylinder, has the idle knob on the left side--cannot see how they could be installed backwards, is a hellish task to install them correctly to begin with. RB
 
#14 ·
you know some times when something looks rather simple and ends up being very difficult, and you have to stand up and get back down after numerous times of getting things out of the way, i wasn't paying attention, they were in correctly. the jets were extremely clogged with goop, i'll drop a picture in here after i get it all back together, still letting a few things soak. it appeared to have like the foam from dilapidated air filter in the bowls, not sure as to what it was but it was nasty. i bet this thing fires like a brand new one when i get it back together!!!
 
#15 ·
Bill, sounds like carbs might be off bike--while things are soaking, charge battery and clean plugs. I would think with all that nastyness you prob sucked some into cylinders and messed up plugs. I would suggest that when you re-install the carbs to fill the bowls with clean fuel before trying to start. The pet cock is vacume actuated, which means with no fuel in the bowls, it takes some amount of cranking to get fuel to fill the carbs. After the carbs are installed, and before attaching the 2 fuel lines to the pet-cock, open the carb bowl drains and introduce fuel into lines , close drains and attach lines to petcock. Will save a lot of cranking! Idle should be 1100 rpms. Good luck
 
#16 ·
Bill, sounds like carbs might be off bike--while things are soaking, charge battery and clean plugs. I would think with all that nastyness you prob sucked some into cylinders and messed up plugs. I would suggest that when you re-install the carbs to fill the bowls with clean fuel before trying to start. The pet cock is vacume actuated, which means with no fuel in the bowls, it takes some amount of cranking to get fuel to fill the carbs. After the carbs are installed, and before attaching the 2 fuel lines to the pet-cock, open the carb bowl drains and introduce fuel into lines , close drains and attach lines to petcock. Will save a lot of cranking! Idle should be 1100 rpms. Good luck
I think you may be over estimating how much cranking it takes to get fuel from the tank to the carb. My bike sat for the whole winter after I had run the carbs dry before storage. So after about 6 months I turned the petcock on, installed a new MF-AGM battery, and cranked for a timed 15 seconds. Waited for 30 seconds to allow starter to cool, then cranked again and it started at 10 seconds on the second try. :smiley_th

No guarantee for the OP that his bike will start that quick, but it may.
BTW billdozer1000, welcome to the Vulcan madness. :beerchug:
 
#17 ·
well, the cranking is held off because i guess when i turned the carbs upside down to clean the bowls and jet (which were extremely clogged up, i guess the bowls stuck open, because after an hour and a half of reinstalling them, i turned on the petcock and gas started comming from places it shouldn't. the only screws i took out were the 4 that hold the two bowls in... i didn't expect this, i've said my share of curses in the past couple hours...
 
#22 ·
need more info--how do you know the floats are stuck--open-closed --?
 
#23 ·
Because I have gas coming out of the hose that goes from the middle of the carbs and V's off to the center of the carbs then returns to the air induction on right side of bike. Its also pouring out of the rear carbs butterfly opening, I just watched the video on the rebuild you have here in the forum, wow that's gonna save my ass!!!
 
#25 ·
Because I have gas coming out of the hose that goes from the middle of the carbs and V's off to the center of the carbs then returns to the air induction on right side of bike. Its also pouring out of the rear carbs butterfly opening, I just watched the video on the rebuild you have here in the forum, wow that's gonna save my ass!!!
Link to Roach`s carb rebuild videos:
http://www.vn750.com/forum/showthread.php?t=19660
 
#24 ·
There should not be a constant flow of fuel to the carbs when the bike is not running, there are 3 lines on the tank petcock, the center one is a vacuume line. The others go to the carbs, there has to be a vacuume felt on the vacuume line for fuel to flow from the tank.
 
#26 ·
today, i got kinda defeated, as assumed that one of the needle valves were stuck open yesterday allowing fuel to keep filling the bowls. so much filling i noticed my oil level had risen and i'm gonna have to change my oil again because i'm sure its full of gas. anyways i went ahead and cleaned the floats and needle valves and blew on the hoses while working the float to ensure they were sealing. they were so this morning i checked my work and function and put them back on the bike. well the same thing happened. then it dawned on me after i pulled them off for the third time that all this vacuum talk should have meant something to me before i started cleaning everything. i haven't messed with the diaphragms yet but i'm sure they are in as bad of shape as the rest of the carb. so tonight i'm gonna take em apart one more time and check those out, and if bad call the kawa shop and get some new ones and possibly some more gaskets of i'm lucky...
 
#27 ·
Bill, when you say same prob, what do you mean? Wants to fire off but dosn't or fuel flowing out carbs? Sorry should have given you heads up about fuel getting into oil--
 
#28 ·
lol i read about the fuel getting into the oil before i bought the bike, but didnt think about it when fuel was pouring out of the carbs. plus i've had the end result in mind instead of taking my time and taking the correct actions to get there. i've been taking short cuts and only doing one thing trying to make it just go instead of doing full inspections. i've been cursing myself all day... (as if three removals and two installs of these carbs wasn't enough) i'm currently taking out the diaphrams one at a time and inspecting them, so i'll likely have answers in an hour or so, but instead of putting the carbs on the bike as a way to check, i'm just gonna put the gas tank in such a way as i can connect the fuel lines and make sure that gas isn't pouring out the bottom before installing
 
#29 ·
does anyone know of a cheaper place to purchase carb parts? the two small diaphragms that i need to replace were 56 dollars each from the kawa shop, i expected 3 or 4 for those little things... the bowl gaskets were 13 and the float gaskets were 11, and the tiny gasket that goes over the little weep hole on the small diaphragm cover was 15 dollars, my wife would kill me if i bought all that... so if anyone knows of a cheaper place to buy this stuff thats reliable I'd be happy to learn them
 
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