Carb vent line route - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 11 (permalink) Old 03-18-2012, 01:14 PM Thread Starter
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Carb vent line route

Trying to put my fuel tank back on, and I think I hooked up the hoses wrong. It seems that the hose from the carbs that forms a tee, is the fuel vent line. I hooked that up to one of the fuel connectors on the shut off valve, and gas leaked all over the engine.

I can't for the life of me figure out where the vent line is supposed to connect to. Any help would be greatly appreciated.....



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Bought 4/2011 28k Miles,
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post #2 of 11 (permalink) Old 03-18-2012, 03:39 PM
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the vent line runs to the right ear.
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post #3 of 11 (permalink) Old 03-18-2012, 03:45 PM
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The stock carb vent system is a poor design. It uses a hose from each carb, then they connect to a T fitting and become one hose, which fits into a clip on the right air filter housing. This setup has two problems. One, using the T fitting cuts the hose inside diameter in half, and the place where the end is supposed to go has been known to plug it up. I took 2 separate hoses, put one on each carb, and ran both of them down below the bike. The ends should be left open. These vents just make sure there is atmospheric pressure in the carb float bowls. The fuel tank vent is supposed to maintain atmospheric pressure in the tank.

I am a motorcyclist, NOT a biker.


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post #4 of 11 (permalink) Old 03-18-2012, 04:08 PM Thread Starter
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Great, thanks. The line had been run to the other side of the bike do I had no idea where it went. The engine also starts hesitating and running very sluggish when I get over 40. Have had the bike apart since november and the gas in the tank is from then. I had put stabilizer in the tank, but could that still be the problem, old stale gas keeping it from running right over 40 MPH?



Pete Herrmann
1994 Vulcan 750 40K on the clock and counting....

Bought 4/2011 28k Miles,
New Rick's Motorsports R/R
Tim Parrot Stator
Tuxedo Mod
KAW Saddlebag/signal relocation brackets
NGK Iridium Plugs
TOC MCCT's
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post #5 of 11 (permalink) Old 03-18-2012, 06:37 PM
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if said hose gets too much air... it causes similar issues to what you describe.
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post #6 of 11 (permalink) Old 03-18-2012, 07:50 PM
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Quote:
Originally Posted by slimvulcanrider View Post
if said hose gets too much air... it causes similar issues to what you describe.
I think this statement needs some explaination for the opening poster slim.

An open hose in calm air shouldn`t be a problem.
The same hose exposed to air moving rapidly at a right angle over the end will cause vacuum or pressure variation in the carb bowls and eratic fuel delivery to the engine, causing symptoms similar to what you are experiencing.

So you need to either tie the hose with the open end facing toward the back of the bike, or put a breather filter on it.

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post #7 of 11 (permalink) Old 03-18-2012, 08:11 PM
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Hey everyone, I'm new to this forum,
just picked up (saved?) an 86 kawi 750, PO has neglected the hell out of it, now I'm working on bringing it back to speed.
I take a look at my carbs and i dont see any vent tubes at all? I attached the 2 side pics below. Can someone help me identify which ports the tubes should connect to? Or do I need to take the tank off to run these lines?

All runs smooth as silk until I hit around 80km/hr and i experience the same symptoms as @peterherrm
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post #8 of 11 (permalink) Old 03-18-2012, 08:20 PM
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Quote:
Originally Posted by ilanm View Post
Hey everyone, I'm new to this forum,
just picked up (saved?) an 86 kawi 750, PO has neglected the hell out of it, now I'm working on bringing it back to speed.
I take a look at my carbs and i dont see any vent tubes at all? I attached the 2 side pics below. Can someone help me identify which ports the tubes should connect to? Or do I need to take the tank off to run these lines?

All runs smooth as silk until I hit around 80km/hr and i experience the same symptoms as @peterherrm
the hoses they are talking about cannot be seen by the angle of your pics. if you look straight down over top the carbs down between them where they vee together they should come straight up and connect to a tee fitting and then route over to your right ear. a lot of us have cut the tube at a 45 degree angle before inserting it into the ear to keep it from bottoming out!

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post #9 of 11 (permalink) Old 03-18-2012, 08:31 PM Thread Starter
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Thanks guys, that must be the problem, too much air. I was testing the engine out with no ears on at all, and I had the hose sticking out the left side, to the air was rushing past it at that angle.....



Pete Herrmann
1994 Vulcan 750 40K on the clock and counting....

Bought 4/2011 28k Miles,
New Rick's Motorsports R/R
Tim Parrot Stator
Tuxedo Mod
KAW Saddlebag/signal relocation brackets
NGK Iridium Plugs
TOC MCCT's
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post #10 of 11 (permalink) Old 03-18-2012, 08:32 PM
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Ah gotcha. Thanks! I'll see what I can do.
The PO must have yanked the vent tubes out because there is nothing going into the right ear and nothing hanging in the vacinity.
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