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Small Air Cooled Gasoline Engines

Keihin Carburetors


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  #1  
Old 06-15-2008, 11:00:45 PM
Bill Sherlock Bill Sherlock is online now
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Default Keihin Carburetors

Friend of mine brought over a Keihin carburetor off an older Honda 50cc bike for me to look at as gas is running out of one of the nipples unless the shut off is closed. I don't have any experience with this make of carb or any specs nor was I able to locate useable info on the internet. I took the top off the carb and sprayed carb cleaner into the various parts and blew everything out with compressed air. Couldn't see anything obviously wrong so put it back together, still leaking as before. At first thought maybe a vent was plugged from sitting unused for about 10 years but don't think that was the case. Needle looks good but can't tell if the seat may need replacing.

Anyone have a parts list and float specs? Only numbers on carb is C50J IL

Thanks for any assistance.

Bill
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Old 06-15-2008, 11:13:45 PM
John A John A is offline
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Default Re: Keihin Carburetors

Bill,
If you find any Honda parts let me know. Been looking for a set of carbs for a '72 CB350 twin.
John
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Old 06-16-2008, 08:27:19 AM
K D Redd K D Redd is offline
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Default Re: Keihin Carburetors

The Japanese carbs like this I have worked on, which have been few, Have a tube which externds above the normal float level but below the level that would allow fuel to flow into the engine. If this is the tube that is leaking it is doing it job but sound like you have a float needle not sealing or a float that is heavy from fuel incursion or varnish build-up.

Kent
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Old 06-16-2008, 09:34:57 AM
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Default Re: Keihin Carburetors

It does sound like a sticking float, or if it is a diaphragm carb, the diaphragm might have some holes in it.
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Old 06-16-2008, 10:28:16 AM
Kevin O. Pulver Kevin O. Pulver is offline
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Default Re: Keihin Carburetors

I think KD and Lead Head are on the right track. Overflow tube.
If it's a brass float, make sure it isn't soaking up gas, (some of the black plastic floats GM used to use would even soak up gas.) probably the needle and seat. Possibly a cleaning would take care of it. Try blowing through the gas line connection with the carb upside down. The weight of the float should shut it off. Kevin
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Old 06-16-2008, 03:39:26 PM
Jonathon Schmidt Jonathon Schmidt is offline
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Default Re: Keihin Carburetors

I may have some carb parts for hondas. I pulled a pair off a cb360. john
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Old 06-16-2008, 06:22:11 PM
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Default Re: Keihin Carburetors

The needles on those little carbs are a pain. If you do not have it completely clean or seated correctly it will blow fuel out of the vent. If the carb has sat empty for awhile then the needle is probably shot. I have not seen too many bad floats but I have seen many misadjusted floats that cause the same result. The main and pilot jets are ultra small and clog easily, always good to pull and clean them while you got it apart.
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Old 06-16-2008, 11:25:43 PM
Bill Sherlock Bill Sherlock is online now
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Default Re: Keihin Carburetors

Thanks for the input guys!

Float looks OK, no buildup and no air bubbles when I submersed it in hot water. Needle doesn't show any sign of wear but I can't vouch for the seat. I don't have the carb anymore or would check it out further. In the meantime the owner is attempting to find a new needle valve and seat as well as the plastic fuel strainer. Without a spec sheet I'm not sure if there is any way to adjust the float which sits over the needle valve. There's a small spring above the float which is held in place on the needle valve by an E clip in a groove. Maybe the spring needs more tension??

Bill
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Old 06-20-2008, 10:32:43 AM
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KeithW KeithW is offline
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Default Re: Keihin Carburetors

On some of those there is a drain screw on the bottom. It needs to be closed. It looks a lot like an mixture adjustment screw on the float bowl. It's used to drain the bowl before storage or transport. Check this link, it's the Honda scooter forum. http://www.hondaspree.net/phpBB2/ They have copies of various service manuals also. A bunch of kids for the most part but generally usefull.

keithw
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