the right carb on my vb21 is overflowing out of the top vent port. I have new float valves and the floats are set to the right height. If I manually lift the float fuel cuts off so it’s not leaking from the valve and the float itself still floats fine in gasoline. Any ideas why it would still be overflowing?
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Keihin vb21b carb overflowing despite properly set float height
Are the new float valves OEM Honda, or aftermarket? If aftermarket, that could easily be the problem as the tend to vary in length.
They’re aftermarket they came in a kit from keyster carbs. If they were the wrong lengths and such then the left carb would be leaking too but that ones fine
Fair enough. LDR has suggested polishing the float valve itself where the needle (valve) seats, there could be some wear or irregularities in the sealing surface. He'll be along later with a lot more knowledge on your model's carbs.
Did you replace valve and seat, or just valve? The aftermarket kits are a problem for their inconsistencies- like having one work fine and another not at all. A quick check is to make sure the valves still have that springy bounce.
If you didn’t replace the seat as well, you can try polishing it - it’s not uncommon to have just enough crud on that to keep the needle from seating.
If you didn’t replace the seat as well, you can try polishing it - it’s not uncommon to have just enough crud on that to keep the needle from seating.
Are your floats adjustable with a metal tang? If so did you check them with the new parts vs the OEM spec for the float height? The aftermarket ones are not always to the Honda spec height for the fuel needle and seat. That one side that is leaking maybe off vs the side that isn't leaking.
If you have a Mitey Vac you can pull vacuum on the fuel line when the carbs are inverted and off the bike to test for leaks past the new fuel valves and seats. Is the brass standpipe inside the bowl solid? They can develop micro cracks, so testing the bowls for them holding fluid is a good idea too.
If you have a Mitey Vac you can pull vacuum on the fuel line when the carbs are inverted and off the bike to test for leaks past the new fuel valves and seats. Is the brass standpipe inside the bowl solid? They can develop micro cracks, so testing the bowls for them holding fluid is a good idea too.
Do you mean on the rubber tip of the valve? Or the brass seat
The seat, where the valve tip seals.
Roll up a small piece of 600 or higher grit sandpaper and twist in the bore. A short tab hanging out below will function to polish the seat itself. I also sand/polish the 4 ribs on the float needle.
However you mention that the fuel cuts off when you manually operate the float which suggests that the overflow stand pipe in the bowl is cracked. Polish that brass tube and inspect closely for a black line running up one side, that's the crack. Use flux and solder it closed.
I was thinking it might be cracked as well but it takes about 20-30 seconds from an empty bowl to leaking gas and it’s coming from the top vent (in the photo) at the exact time the overflow at the bottom starts spilling. I’m about to polish the seat though.
Coming out the vent means the float needle isn't sealing for one reason or another. Sometimes the taper of the needle is distorted or dirty.
mine was perfectly fine it in fact wasn’t sealing right so polishing it did help! It’s back up and running now I have to clean the choke circuits cause suddenly the choke is half useless
There are no choke circuits, just the choke flap.mine was perfectly fine it in fact wasn’t sealing right so polishing it did help! It’s back up and running now I have to clean the choke circuits cause suddenly the choke is half useless