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Author Topic: Leaking cabs  (Read 438 times)
Rexeriot
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« on: June 29, 2019, 10:33:36 AM »

Hi . Bike runs well but have noticed that fuel is now leaking from the float bowls on no 1 and no 4 carbs. They were only off and cleared a few months ago. Needle valve sticking possibly but on both at the same time?  Any help greatly received
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a_morti
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« Reply #1 on: June 29, 2019, 02:11:08 PM »

If it runs fine then the needles probably aren't stuck.

New seals may solve it
https://litetek.co/Carb_Kit_Honda_CB1_NC27.html
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filterMan
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« Reply #2 on: June 29, 2019, 02:12:57 PM »

It could be bad stuck float valves. The Honda part number is 16011-KY2-711. You don't list your location but if you are in the UK they are listed at NRP (link below) as in-stock and not a bad price either.

http://www.nrp-carbs.co.uk/shop/index.php?route=product/product&keyword=Honda%20cb-1&product_id=4612

Hope this helps, Cheers, Al
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a_morti
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« Reply #3 on: June 29, 2019, 03:54:07 PM »

Bike's running fine so doubt it's floats. To be sure, check if the oil level is higher than expected.

Seals can be ok but then fail if disturbed, which op said the carbs were cleaned. That's all it want, new seals.
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Rexeriot
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« Reply #4 on: June 30, 2019, 10:40:13 AM »

Thanks guys as always.  Probably just dodgy seals as bike runs well .. and I mean really well. Amazing little thing
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filterMan
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« Reply #5 on: July 01, 2019, 09:16:09 AM »

a_morti, this is interesting and I'm sure you are right. I assume that there is fuel flow between top and bottom of the carb so if the seal goes bad it will leak.

But, if the valve seat is worn so fuel leaks past it, wouldn't fuel just pee out of the carb somewhere? Just like when your toilet cistern valve goes bad. How would that affect the running of the bike, if the fuel level is high in the float bowl what effect does that have on the running? Metering is still done by the jets right, or is my understanding wrong? Probably is Grin
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a_morti
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« Reply #6 on: July 01, 2019, 04:46:16 PM »

I'm just running on the theory that fuel in the bowl is seeping past a crushed float bowl seal.

If it were the needles, I'm pretty sure it'd run bad. Otherwise why bother setting float heights at all?
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Spurlock
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« Reply #7 on: July 02, 2019, 12:44:15 PM »

You might want to check that a couple of float bowls are not switched. When I got my bike there was slight leaking from one float bowl gasket. I replaced all four but the leak persisted. Looking again I saw that there is a small boss at the right or left (depending upon which carb) front corner of each float bowl that acts as a stop for the limiter flag on the idle mixture screws. The previous owner had swapped two float bowls and on one the boss hit the carb body, preventing the bowl from completely seating on the float bowl seal. It only held the float bowl away from the carb a slight amount, but it was enough to cause a seepage of gas even with new seals.

-Bill
« Last Edit: July 05, 2019, 04:03:07 PM by Spurlock » Logged

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Efreeman55
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« Reply #8 on: July 02, 2019, 01:14:49 PM »

One day I developed a fuel leak and it turned out to be the seals between the fuel tubes connecting the carbs.  Fitted a LiteTek kit and all was well again.  Just age had deteriorated the OEM seals.

Eric
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See Bee-Won
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« Reply #9 on: July 03, 2019, 09:08:34 PM »

You might want to check that a couple of float bowls are not switched. When I got my bike there was slight leaking from one float bowl gasket. I replaced all four but the leak persisted. Looking again I saw that there is a small boss at the right or left (depending upon which carb) front corner of each float bowl that acts as a stop for the limiter flag on the idle mixture screws. The previous owner had swapped two float bowls and on one the boss hit the carb body, preventing the bowl from completely seating on the float bowl seal. It only held the float bowl away from the carb a slight amount, but ity was enough to cause a seepage of gas even with new seals.

-Bill

If the OP has to take the bowls back off to replace the o-rings he might as well dremel those limiter taps off while he's at it. I never realized how smooth my bike would idle until I gave each mixture screw a half turn out from the lean factory settings. Nice steady beat now and sharper throttle response when you crack it.
« Last Edit: July 03, 2019, 09:10:28 PM by See Bee-Won » Logged
RVFRick
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« Reply #10 on: July 16, 2019, 10:42:22 AM »

It could be bad stuck float valves. The Honda part number is 16011-KY2-711. You don't list your location but if you are in the UK they are listed at NRP (link below) as in-stock and not a bad price either.

http://www.nrp-carbs.co.uk/shop/index.php?route=product/product&keyword=Honda%20cb-1&product_id=4612

Hope this helps, Cheers, Al


Hi Al, I've never looked at my CB-1 carbs. I am curious that the NRP listing states "valve + seat". By seat do they mean the rubber tip portion of the needle or the carb side of the valve function? If it is on the carb side how is the seat removed and installed? On my NC35 the seats are brass and pressfit but not replaced as far as I know. Can they actually wear out given the metal is much harder than rubber?


* Screen Shot 2019-07-16 at 7.36.38 AM.png (104.75 KB, 789x477 - viewed 23 times.)
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Spurlock
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« Reply #11 on: July 16, 2019, 11:09:38 AM »

Hi Rick,

The CB-1 carbs use a hex head threaded brass seat, so needles and seats are included in the NRP sets, photo below. I've never seen replacements for bikes with pressed-in seats. As you imply, they simply don't wear since the needle tips are soft.



-Bill
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Spurlock
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« Reply #12 on: July 16, 2019, 11:19:33 AM »

I suspect the reason the CB-1 seats are easily removable is to allow cleaning/replacement of the attached filters. The non-removable seats I've seen do not have filters.

-Bill
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filterMan
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« Reply #13 on: July 16, 2019, 03:30:25 PM »

Hi Rick,

In answer to your question...Can they actually wear out given the metal is much harder than rubber?

I was actually just guessing, I've not had this problem with my -1 but I did have that exact problem with a car I had years ago. If the valve is rubber tipped then it perishes and fuel overflows. I'm not sure how much more reliable metal tipped ones are but they might suffer from dirt or old fuel perhaps.

Cheers, Al
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