carb vent hose - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

 
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post #1 of 9 Old 09-02-2014, 07:52 PM Thread Starter
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carb vent hose

Does the carb vent hose have to be a certain length?

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post #2 of 9 Old 09-03-2014, 08:48 AM
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No.

Stock, it ends about 10" above riding surface.

Yet . . . unless you perform the "Tee mod" (putting tee fitting in hose and routing a hose on its auxiliary end upward, as in, under the seat or at the steering head), you will not survive a water crossing deeper than . . . about 10"!
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post #3 of 9 Old 09-03-2014, 01:42 PM
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Gen2 I have noticed have the bowl vent hose run along the frame to a much shorter length. You will already know about the bowl vent "Tee Mod" but I find it ironic that Gen1 and Gen2 both need the Mod because each generation has only one but opposite hose routing. :-)

Water crossings are not the only issue for Gen1 as I experienced the symptoms on my first ride in the rain on my new KLR many years ago. I think that was the first mod I did to a KLR.

IMO, the downward run of hose from the tee doesn't have to be very long although I like a foot or so working under the assumption that this drop length is more likely to clear water than a shorter.

Someone much smarter than I (apologies as that doesn't reduce the number of potential candidates very much) recommended cutting a long "V" slot into the end of the vent hoses to break the water drop inside the hose. Sorry, poor description but you will know what I mean.
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post #4 of 9 Old 09-03-2014, 05:43 PM
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Quote:
Originally Posted by Normk View Post
Gen2 I have noticed have the bowl vent hose run along the frame to a much shorter length. You will already know about the bowl vent "Tee Mod" but I find it ironic that Gen1 and Gen2 both need the Mod because each generation has only one but opposite hose routing. :-)
While some Generation 2 owners install the Tee Mod, I do not see any advantage over the OEM configuration regarding avoidance of water-crossing stalls. The end of the Generation 2 vent hose is about 30" above the riding area (under the seat); a water crossing that deep might be hard to survive, regardless of carb vent hose numbers or routings.

A Generation 2 Tee Mod with an auxiliary downward-routed hose can allow any moisture accumulating in the vent system to drain, however.

Last edited by Damocles; 09-03-2014 at 05:46 PM.
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post #5 of 9 Old 09-03-2014, 07:48 PM
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Have another look at the routing of your Gen2 hose and see if you concur.

It runs "uphill" and back, in the manner we usually run the extra/new hose from the "Tee Mod" tee. Problem is, in deep water and or directed spray in which water enters the vent hose, the water must run "down hill" into the carb.

I cut the Gen2 hose in order to install a tee fitting, then run a drain hose downward in the manner of the Gen1 hose. Seems like an obvious and simple prevention of a potential PITA problem.
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post #6 of 9 Old 09-04-2014, 06:17 AM
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Quote:
Originally Posted by Normk View Post
Have another look at the routing of your Gen2 hose and see if you concur.

It runs "uphill" and back, in the manner we usually run the extra/new hose from the "Tee Mod" tee. Problem is, in deep water and or directed spray in which water enters the vent hose, the water must run "down hill" into the carb.

I cut the Gen2 hose in order to install a tee fitting, then run a drain hose downward in the manner of the Gen1 hose. Seems like an obvious and simple prevention of a potential PITA problem.
Conceded by my comment, "A Generation 2 Tee Mod with an auxiliary downward-routed hose can allow any moisture accumulating in the vent system to drain, however."

Unless the volume of water entering the Generation 2 vent hose (at 30" above the riding surface) is sufficient to stop it up completely, I think the effect would be more-or-less benign; would not defeat a nominal water crossing (even greater than 10" depth), as with a stock Generation 1 carb vent hose placement. Without a Tee Mod, a Generation 1 is stopped in its tracks on deep water crossings; Generation 2, not so much (water less than 30" deep).

Still, water in the mixing chamber, beneath the diaphragm, isn't welcome; I see the advantage of the Tee Mod for Generation 2s for drainage purposes.
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post #7 of 9 Old 09-04-2014, 12:25 PM
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If one is retired and bored, dipping the end of the bowl vent hose into some water while idling can be an interesting experiment. The water will not lift very far in the hose and withdrawing the hose from the water will usually see the water column remain suspended in the hose. The engine will react to the effect on bowl air pressure when throttle is varied.

I wouldn't do this with the "down hill" Gen2 hose unless a drop hose is attached so that the hose has a foot or so of rise as water might be pulled into the carb. Interesting on a Gen1.

It shows how water can remain within a vertical hose of small enough diameter to allow the combination of surface tension and pressure difference to hold the water in place.

Slicing the end of the hose into a pair of long "V" notches seems a good practice.
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post #8 of 9 Old 09-05-2014, 09:25 PM
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I route all of the Gen 2 pink carb air vents 'up and over' the frame, down to the top of the shock, at initial prep or break-in maintenance!
Cut at a 45 degree angle, at the tip.

I think, car-wash water could possibly enter the hose as factory installed!

pdwestman
Modify at "YOUR OWN RISK"!

Still riding my 1987 KL650-A1. 85,000+ miles & counting
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post #9 of 9 Old 09-05-2014, 09:40 PM
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Good to know.

Thanks, Paul.
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