Cb550f1 carb petrol coming out of overflow

[Glynnrg]

Morning to all
I have removed the carbs and cleaned fitted rebuild kit the rebuild kit came with 3 small rubber o rings not sure where they went and looking at other rebuild kits u could get they wernt always included (so didn't fit them)
Before I fitted them back on the bike I put petrol through them on the bench one of the carbs is still leaking via the overflow is this the norm or have I still got a problem
Any ideas what could be causing this and any solutions
Ps the floats don't seem to be sticking
Many thanks and a happy new year

[kevski]

If you have replaced the needle valves and seats this is probably the cause, i have always found the replacement parts not quite up to the job, so now when i do this job on any carb i polish the tip of the valve  and the seat gets a small going over also, to do this i get a piece of stiff card and put a hole in it using a sewing needle i then put a speck of autosol on the hole and push the float needle into it twisting it back and forth i normally do this for about a minute just to polish it up slightly, i then clean it up using white spirit, the seats i polish slightly using autosol and a wooden cocktail stick for about the same amount of time and clean off again with white spirit this takes of any slight burrs on the parts which can let fuel by, i have been doing this for many years and it always works, i also use in-line filters to ensure no particles from the tank get in the carbs and cause problems.

[Glynnrg]

Thanx I'll give it a go

[mickwinf]

dont do this if they are rubber tipped

[kevski]

dont do this if they are rubber tipped

Of course not, i should have stated that, but common sense is something that should realize that, they should be all metal needle valves.

[Seabeowner]

There was a problem on early CB500s with cracks in the brass overflow tube.

[Glynnrg]

Am I looking into this tooo deep I have tried the autosol remedy put fuel through the carbs bearing in mind I am doing this on the bench if I turn the petrol tap I don't seem to get fuel out the overflow unless I give them a fist full of throttle then only one them leaks out of the overflow ??

[paulbaker1954]

Glynn,

I share your frustration having just been through a similar set of circumstances. I rebuilt my carbs using the full kit from Rocky Riders in the US as the pricing was very good. The needles and jets were fine but the float valves were not. I had exactly the same issues as you have. In the end I changed the float valves back for the original ones but with new O rings and all is now fine. Here are some useful things to try

1) On the bench hook up a plastic" manometer" tube in to the drain hole, turn fuel on and see how the level goes. It should just rise until the valve shuts off the supply. What I found was that it would rise and then VERY SLOWLY continue to rise to eventual overflow because the valve is not seating fully.

2) Obvious but at the same time check the float level

3) Fine emery the float pin just in case the float is sticking

4) Swap the fuel bowl over as there is a tendency for the brass overflow tube to develop a hairline crack (It happened to two of mine) that can show the same symptoms


In the end I have come to the conclusion that where float valves are concerned stick to OE. They are a lot more pricey but saves a lot of aggro in the long run.

[Glynnrg]

thanx paul