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Discussion Starter #1
Okay took the 96 Vulcan 750 to get inspected today and noticed that it seemed to be at a loss of power. Tried starting out in first gear and felt like fourth gear. Got out on the highway and opened the trottle an it had no power and would not go past 5000 RPMs. I just recently purchased the Vulcan and it set for 4 yrs. Here are the things that I have done so far.
1. Added Sea Foam to gas when first purchased and continue to do so
2. Changed plugs, oil and filter
3. All four plugs are firing (tested)
4. Starts great don't even need to choke it all the way
5. Idles at 750 no backfiring when riding
6. Changed ACCT springs no knocking
7. No gas leaking out of overflow tubes
This really has me stumped it seems as though the bike has no get up and go, rides like a moped. As I stated there is no backfiring just lack of power and not going over 5000 RPMs. Is there anyway that I can check to see if the cylinders are getting fuel it seems as though it is running on two cylinders, you know that lack of power sound in the exhaust that you just know it is not getting its full potential in power. Any help would be great I am ready to ride but not a moped. Thanks for any help in solving this problem.

Bill
 

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you might try checking the carb vent hose that goes into the right air filter housing. Take the hose out and cut it at a 45 degree angle and then reinsert it. Mine was having the same problem and seemed like it was starving then thanks to this site I tried that and it ran perfect. Seems to be a pretty common problem. Do a search on vent tube or similiar for more info or wait for some other replys. Here's one thread on it: http://www.vn750.com/forum/showthread.php?t=3393&highlight=vent+tube
 

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Discussion Starter #3
Well took the covers off the filters and noticed the filters are just crumbling apart, could this be the cause? I checked all the hoses and everything seems fine but will probably end up replacing them due to how long it sat for.

Bill
 

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Well took the covers off the filters and noticed the filters are just crumbling apart, could this be the cause? I checked all the hoses and everything seems fine but will probably end up replacing them due to how long it sat for.

Bill
I was jsut going to suggest you do that, but then realized there were a couple of posts after your initial one. Yes, indeed, that can cause all kinds of trouble - your carbs need good, clean air to run properly. Change the filters (and maybe see if there's any junk in your ducts and airbox), and see if things run a little better.
 

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and the Adventure Cycle
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noticed the filters are just crumbling apart, could this be the cause?
As I've mentioned here a few times, when I rode with the filter covers removed, the bike ran just fine....... up until around 4000rpm's.

Hopefully replacing the filter's will fix things right up for ya. :smiley_th
 

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Hyper, do you remember a post...maybe from last summer...where someone said s/he used material from an old t-shirt as a substitute? I recall someone else saying, "What are you doing?!", but I was thinking Bill could do that until he gets some real filters from the dealer. Definitely not a long-term solution, but short-term?
 

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Hyper, do you remember a post...maybe from last summer...where someone said s/he used material from an old t-shirt as a substitute? I recall someone else saying, "What are you doing?!", but I was thinking Bill could do that until he gets some real filters from the dealer. Definitely not a long-term solution, but short-term?
With the filters crumbling apart, if I were to try that, I'd put the material on both sides of the filter, to keep pieces from getting into places it shouldn't be.
And it was Artman who did that. HERE is the post (second down from the top)
 
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Dag, that was quick! I need some journal articles - can you search a couple of databases and have the pdfs to me by, oh, 6.30 am? :rockon:

You're awesome, Hyper, thanks! Bill, check the thread and see how Artman did it.
 

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and the Adventure Cycle
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Dag, that was quick! I need some journal articles - can you search a couple of databases and have the pdfs to me by, oh, 6.30 am? :rockon:

You're awesome, Hyper, thanks! Bill, check the thread and see how Artman did it.

LOL, well, it's after 6:30 now, I might have trouble going back in time !! LOL
 

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Actually that tee-shirt thing worked pretty well. Never had any intake problems. Pull off the foam and fit the cut material around the screen and secure at the base with thick rubber bands. Two layers of material works fine


PS. I now have UNI PODS on, along with the ear shave.
 

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Discussion Starter #11
Okay put the new filters in, still the same problem. Feels like two cylinders are not getting fuel to them. I looked at the fuel system and noticed that there is a fuel filter on the fuel line could this cause the problem? I am at ends with the Vulcan and do not know what to do. The bike idles great, no missing and all four spark plugs are firing, it is just a lack of get up and go like two cylinders are not getting fuel. Is there anyway to test the carbs to see if they are putting fuel to the cylinders?

Thanks
Bill
 

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find out which (front or back) CYLINDER is not running right (note the VN750 has ONLY two cylinders - two plugs per cylinder).
 

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has it ever run right since you've owned it , if not it could be valve timing or badly set up carbs or even choke valves stuck open/cloged main jet /split carb diaphrams , allso i would check that the carb sliders move freely (take the tubes off the back of the carbs and move them up and down by hand ,i have known them to stick if not used for some time) hope this helps.
 

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Edalbris,
I agree, I have to believe it's in the vacuum diaphragm/needle assembly.
Along with a filthy carburetor altogether.
 

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Discussion Starter #15
Just came back from checking the Vulcan, pulled the rear cylinder spark plug cap and the bike bogged down, put back on and idled smooth. Pulled the front cylinder spark plug caps got shocked on both sides so getting spark and the big remained idled. Seems as though the front cylinder is not getting fuel to allow the plugs to fire. Does this mean ripping apart the carbs cause I am not an expert at carbs or could it be something simple?

Thanks
Bill
 

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those carbs have got to come off and probably and rebuild is in their near future. look on the bright side you get to practice on the first and the second is going to be a piece of cake. it will be worth it when that bike is flying down the highway with you on it after you finish.

ride it safe J
 

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Discussion Starter #17
Do you really think that they will need rebuilt because the Vulcan has less the 4 thousand miles on it. It sat for over 3 yrs.

Bill
 

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setting over three years is the problem. Gas will turn to varnish in that time. You can try a seafoam filled carb and let it set to see if that will help.

Drain the carb float bowl for the front cylinder of gas keeping track how much came out. I would go the a farm & fleet store and get a 60ml (or whatever is the biggest cheap plastic) sryinge and go to ace to get some clear palstic tubing to help with the task. Fill up the float bowl (maybe 5ml extra) with pure seafoam and let set for a couple of days then drain the seafoam and try to see if it runs any better.
 

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Just came back from checking the Vulcan, pulled the rear cylinder spark plug cap and the bike bogged down, put back on and idled smooth. Pulled the front cylinder spark plug caps got shocked on both sides so getting spark and the big remained idled. Seems as though the front cylinder is not getting fuel to allow the plugs to fire. Does this mean ripping apart the carbs cause I am not an expert at carbs or could it be something simple?

Thanks
Bill
Bill,

You say you got shocked when you pulled the front caps? Where the caps all the way off of the spark plugs? When I bought my 93 vulcan last year (3800 mi) I found that a couple of the spark plug caps had developed cracks along the mold seams. I noticed the problem when I took the bike out at night and saw sparks between the cap and the cylinder. If yours is doing the same it could cause a loss of power in the front cylinder.

Bob
 

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Bill,

You say you got shocked when you pulled the front caps? Where the caps all the way off of the spark plugs? When I bought my 93 vulcan last year (3800 mi) I found that a couple of the spark plug caps had developed cracks along the mold seams. I noticed the problem when I took the bike out at night and saw sparks between the cap and the cylinder. If yours is doing the same it could cause a loss of power in the front cylinder.

Bob
Had that happen when my caps started to fail. From what is posted, I would wrap the plug caps with electrical tape and if this cures the problem, then replace the wires with new NGK caps and wires. Not a hard job to do - took me under 20 minutes to do all four wires...
 
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