Keihin CVK32 Carb Float Bowl Overflow

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Keihin CVK32 Carb Float Bowl Overflow

Postby n3303j » Tue Jan 13, 2009 2:07 pm

I'm starting to get random overflow from my LH carb when the needle fails to shut off the fuel supply as the bowl fills.

My carbs are shiny/clean and all passages cleaned with compressed air. When the needle seals all runs excellently. When running at road speed all runs well because fuel consumption exceeds the leak speed.


The first sign is a LH cylinder drop out at idle because the mixture has become too rich because of the high fuel level. A MAJOR sign is a hydraulic lock when the LH cylinder fills with fuel if I forget to shut the petcock.

The line is filtered. The condition seems more prevalent when the outside temps are below 30F. A Google search brought up a bunch of comments on this issue with the Keihin CVK used on a quad.


The quad group didn't seem to have any definitive answers for this problem.

Anyone hre had this problem and came up with a good resolution.

Thanks, Ron Cichowski
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Re: Keihin CVK32 Carb Float Bowl Overflow

Postby berger » Tue Jan 13, 2009 2:29 pm

n3303j wrote:I'm starting to get random overflow from my LH carb when the needle fails to shut off the fuel supply as the bowl fills.


How new is the bike? Perhaps the dealer should look at the carb.


The first sign is a LH cylinder drop out at idle because the mixture has become too rich because of the high fuel level. A MAJOR sign is a hydraulic lock when the LH cylinder fills with fuel if I forget to shut the petcock.


How do you shut off the Petcock? Unless you changed it out for another, most have a vacuum controlled petcock. All I have is on, prime and reserve. Perhaps you are leaving it on prime?

The line is filtered. The condition seems more prevalent when the outside temps are below 30F. A Google search brought up a bunch of comments on this issue with the Keihin CVK used on a quad.


I ride an 07 Patrol and I do not use inline filters. Only the petcock screen, and have never had fuel delivery issues.

Berger
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Postby n3303j » Tue Jan 13, 2009 3:03 pm

Bike is a 1997 Sportsman with a 2006 750CC engine. The transmission is the 650 kickstart 4 speed. The rear end is a selectable 2 wheel drive (not the Sportsman full time 2 wheel drive unit). so I have a Frankenbike.

Bike has passed by 5 previous owners in its 11,000 kilometer history. All dealers are "longtime out" of the equation.

The petcock is the original sportsman petcock with Run=Down, Reserve=Up, Off=Left or Right. I'm assuming the vacuum actuated petcock on the newer bikes was a "fix" for the leaky keihin carbs?? That way you won't burn your garage down on an overnight fuel spill.

Your '07 Patrol probably has a nice clean tank that is being kept dry and full of clean fuel. Mine is not bad but the extra screen won't hurt anything.

Sort of like "can't be too rich, too thin or too good looking". Fuel can't be too clean as long as filter flow rate matches consumption rate.

Ron Cichowski

http://www.kayakpilot.com/ural.html
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Postby chicagorandy » Tue Jan 13, 2009 3:03 pm

A very common issue. It's caused by a small booger on the float valve. Simple cure? Drain the offending bowl, remove fuel line at filter going to that carb and blow a couple puffs of air thru the carb inlet using the air pump in the trunk with its attached little red nozzle. (yes THAT'S what that thing is for)

Close the bowl drain. Turn on the fuel. Ride in peace. Problem solved.

Back home when you have nothing better to do you can always drop and clean the float bowl, but often just the air puffs do the trick.
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Postby berger » Tue Jan 13, 2009 3:10 pm

Randy's fix should work, but I thought you mentioned you cleaned eveything out with air. Definitely do that if you haven't already.

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Postby George Butz » Tue Jan 13, 2009 3:38 pm

My right carb started doing it out of the blue just yesterday. :x
Just did Randy's routine and all was well.
I don't run any filters, as the new valves have fine screens. :oops:
This is the first time it overflowed since the rig was new.
Just a part of the "Ural Experience" . We were given air pumps for a reason. :lol:
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Postby chicagorandy » Tue Jan 13, 2009 5:40 pm

On a plus side, it 'usually' only happens once or twice in a lifetime, which is why it doesn't get a lot of mention. But it is one of 'those things' that you learn first hand about the Ural experience. It is right up there with the unexplained racing full throttle caused by the ferrule hanging up on the splitter. Makes for a dramatic starting event when it happens - :)
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Postby BillyG » Tue Jan 13, 2009 7:39 pm

Other than the "bugger" sticking at the float needle inlet (or on the tip of the needle), the only other things that will cause the carb. to flood out is a cracked float (fills with gas and keeps needle from closing), damaged tip of float needle or needle is improperly seated on float tab. If it is intermittent, you have crap that needs to be cleaned out...it is is full time...check for the above. They are rare occurrences, but due happen.

If the crud sticking in the float inlet is gummy, blowing it out may not totally get rid of it. Also, If using compressed air, drop the bowl and remove the float/needle to prevent damage. Even if using a hand pump it isn't a bad idea to drain/remove the bowl.

Get rid of the in-line fuel filters...as you can see, they don't do diddly and your fuel feed will be better.
Bill Glaser
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The "Unofficial Ural Service Manual" can be viewed at: http://www.myural.com
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Postby greenmachine » Wed Jan 14, 2009 10:45 pm

What Randy and BillyG said...

First try to blow the usual booger out of the float seat and give that a whirl. This works 99 percent of the time.
If it's been cleaned and looked at and the seat looks good and seals when tested by hand... then the float is sinkin probably.
I've heard that you can "heat weld " the plastic floats, but I've never tried it myself.

Your carb should not leak a drop into the cylinder whether or not the petcock is closed. If it does, then the float valve seat is leaking for one reason or the other. Either the seat actually leaks or the valve is not bein closed by the float since it has gone all Titanic on ya... or the float hinge/height is messed up and needs to get a bit of a tweak. These carbs usually run pretty decently for very long periods without any messin...
A bit of rusty crud or flaky grey paint chips in the tank can make the carbs act up. It never hurts to flush the tank and petcock real good if ya have stuff in there.

YMMV

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