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Ok before you go making fun, I am a true newbie. so if I don't mention the correct name for a part don't laugh. I got a 1990 Vulcan 750. I always wanted a bike and this one came free from a client. I changed all the fluids - bought new air filters - bought carb boots. I had a fuel leak that was coming from the hoses on the carbs. fix that. removed mostly all the rust from various places. My current dilema is that now my fuel leak is coming from the left side of the air box. HOW AND WHY WOULD I BE GETTING GAS IN THE AIR BOX. Most important how do I make it stop.
 

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My dad's 1986 did the SAME thing. The problem turned out to be, the Fuel petcock was shot, so it was ON PRIME all the time! the weight of the fuel in the tank caused it to slowly seep from sitting. it leaked into the FRONT cylinder and past the rings, and into the crankcase. there was about 1.75 gallons of oil/gas mix in there. We rebuilt the fuel tap. changed the oil. fresh filter. Ran it. and no problems since. i gauentee this is your problem. has the bike been sitting before you aquired it? cuz his was sitting for atleast a year with a leaky fuel tap.
 

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And welcome to the forum!! Check in on the "newbie" forum. Tell us more aobut your bike! miles? mods? condition? Goodluck! hope i helped!
 

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Headbanger/Popes of Hell
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welcome to the madness! don't worry, nobody is going to laugh at you (only with you!). we have nothing but the best people on here that are willing to help you out with you bike or anything!
 

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I agree it's the petcock
 

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I'd start there man. Order the rebuild kit. Have it done in no time. and you should be on your way. However. make sure no gas gets into your crankcase. that could be VERYYYYY bad if it did and u didnt know. luckily we caught it before we road it.
 

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Patriot Guard Rider
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My dad's 1986 did the SAME thing. The problem turned out to be, the Fuel petcock was shot, so it was ON PRIME all the time! the weight of the fuel in the tank caused it to slowly seep from sitting. it leaked into the FRONT cylinder and past the rings, and into the crankcase. there was about 1.75 gallons of oil/gas mix in there. We rebuilt the fuel tap. changed the oil. fresh filter. Ran it. and no problems since. i gauentee this is your problem. has the bike been sitting before you aquired it? cuz his was sitting for atleast a year with a leaky fuel tap.
Probably is the petcock, but the prime position is only found on the earliest 3 or 4 models from 1985 to `87 or `88.
Your `90 petcock does NOT have a prime position, but could still leak if the diaphram is broke. A rebuild kit will probably fix it.
Check the inside of the tank for rust or any other crud inside while you are working on it, and clean if needed.
 

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I was wondering that also, my 2001 has off, on, and res. i dont like this. because i drained my bowls to check for rust or any junk. and it was a pain getting it to restart cuz i couldnt prime it! :(
 

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Discussion Starter #10
Yes the bike has been sitting for some time (not sure how long), thanks for the reply will check it out tomorrow and post back with results
 

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good. we'll be wating..... haha
 

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Discussion Starter #12
@ 1986vn750 How will I know if it got into the crankcase.
 

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Discussion Starter #13
@1986vn750, How will I know if it got into the crankcase?????
 

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Linkmeister Supreme
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I was wondering that also, my 2001 has off, on, and res. i dont like this. because i drained my bowls to check for rust or any junk. and it was a pain getting it to restart cuz i couldnt prime it! :(
With a good battery just crank it over to create vacuum to the petcock which allows fuel to flow by gravity to the carbs. Should only take 15 or 20 seconds to fill the carb bowls with gas with the petcock in the ON or RES position. My `91 sat for almost a year and a half without being started after my accident, and after installing an MF battery last spring it fired up within 20 seconds.:smiley_th
 

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Hoss, a simple prime position would make it start in 2 seconds and save all that wear on the starter! haha and you'll know by smelling the filler cap for oil. you should not smell any gas.
 

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Plus, the oil will likely be over-full. Check the oil site glass with the bike on the centerstand and you should have a bubble near the top of the glass. Definitely smell the oil though. It shouldn't smell like gas.
 

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Discussion Starter #17
ok guys, I unscrewed the oil cap and smelled it, it does smell like gas...:(. Now What? how bad is that?
 

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You'll need to change your oil. Wait til you fix the problem so you don't keep flooding your crank case with gas and have to do it again. Don't run the bike with the gas in the oil though!
X2. I think Fergy is right on the mark with his advice.:smiley_th
 
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