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Discussion Starter · #1 ·
So I’m in the process of purchasing a 93 Vulcan (UK),
I’ve done a lot of work on my own bikes, I do my on servicing troubleshooting and parts replacements, however living in the uk I was restricted to a 125 for some time so quite a bit different than what I’m used to.
After gaining my full licence, I set to work on the vn that my father in law had for me, the bike has sat for seven years (when it was last taxed, still has the tax disc on) with fuel in the tank and carbs. All in all it has been kept very well during that time.

So with the manual in hand I set to work draining the tank, and pulling the carbs for cleaning and replacing the jets and o rings, all went together nicely and back on the bike PITA as it was.
Spark plugs and battery have been replaced. Spark on all four.
The petcock was leaking fuel even after a rebuild kit, so I did away with the diaphragm and placed a gasket over that side, vac hoses also plugged, no more fuel leaks and the bike is getting fuel (undid the Allen screw on the bowl to check) My issue at the minute is it will only idle, as soon as you touch the throttle it bogs and dies, I’ve had it out on the road and if you can make it past the bog say downhill it will come to life and start to pull.
Not sure all that information is relevant for a new members post but looking for help
Many thanks Dave
 

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Discussion Starter · #3 ·
I will say I was very thorough when re assembling the carbs, checking the action of the slides, needles correctly seated and butterfly’s operating etc not wanting to ever take them off again. I will re check however. After reading some other posts with similar issues, Im going to try some seafoam tomorrow seeing as the bike idles should be sufficient to pull it into the carbs no?
I should also have mentioned no modifications other than the leaky petcock and carb overhaul have been made to the bike, everything is stock
 

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FREEBIRDS MC CENTRAL NY
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Welcome to the nucking futhouse

Sent from my A501DL using Tapatalk
 

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Discussion Starter · #7 ·
Thanks oledirtydoc what a machine! I’ve had a look at the bike today, slides and diaphragms on the carbs are working fine, I did notice fuel sputtering out of the air intake so it’s clearly not a lack of fuel delivery issue, could the bike be running that rich?
Quick recap on my petcock bodge job, so original and new diaphragm were no good, I got rid and just put a gasket on and sealed it up, so now the bike has on off or res just got to remember to turn it off! (As far as I understand) The vacuum ports are capped. None of the fuel lines are running uphill.
Pulled the plugs (although they’re new), they were really fouled, cleaned them up and the bike ran much better. It will still idle fine but spit and sputter and backfire at around 2k, once your past that it’ll redline.
My next thought is maybe a stuck float needle despite replacing them, a fleck of paint could be preventing it from closing, or I’ve perhaps installed the incorrect jet size when replacing them, which will be impossible to know at this point, I shall take the carbs off again and have a thorough look through everything. Or possibly a weak spark issue, let me know your thoughts and thanks for your help so far guys!
 

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VN 750 1994 RED/BLACK/SILVER
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  • If you do away with vacuum pipes then the petrol tank can't deliver fuel as it should, because the vacuum pressure on the petrol tank is out of balance and the carburettors can't synch properly and pull the fuel through! That how it is with Eliminator's. You can go to a non- vacuum tap which works differently, you turn this type on and off.
  • Once an engine runs and "breathes" in the four stroke cycle, all kinds of pressures are set up in induction, compression, firing and exhaust which CV carburettors try and iron out along with the air-box and exhaust system.
 
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