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R75/5 float/needle valve issues.

10drum

10drum

New member
I changed everything in the carburetors except the floats and pins. I put about 1 1/2 gals in the tank, I got everything dialed in, the bike runs great. I filled the tank, then the right carb started leaking, after it sits for a few minutes. Then, I installed new floats and pins in both carbs. The right carb will still leak if both petcocks are open, or if the bike is on it’s kick stand. The bike is still running good. Closing the petcocks after a ride is common nature for me......most of the time. I’m suspect of the float valve seat???
 
Or some debris in the tank that's holding open the valve? Also, sometimes the action of the rising float doesn't necessarily push the valve up evenly.

Try putting the bike on the center stand with fuel in the tank. Closed petcocks. Remove one float bowl. Be ready to catch the fuel as it flows. With your gloved finger, hold the petcock up so you're sure that the valve is seated...open the petcock. Is the fuel not flowing? Can you drop the float a skoosh and get the fuel to flow out, then raise the float to stop the flow of fuel? Try those sorts of things to convince yourself that the float and valve actually seat. If they don't with the float bowl back in place, you'll need to look for the reason why.
 
I had a similar problem. On mine, there was no way to replace the float needle seat. The seat was recessed up in the hole. So, what I did was to take a paper punch and punch out several pieces of very fine wet or dry sanding paper (the black stuff, about 400 grit) and glue that piece on the top of the eraser of a pencil. I then inserted in hole and spun the pencil for a while. Did a second time - each time got some of the original seat on the paper.

Re-assembled, set the float level, made sure things were flowing and shutting off by lifting the float up and down. Put bowl back on.

NEVER had a leak again!! Even after 3 more years! Of course, this was after having completely cleaning out the tank and petcocks. I also used the in-line filters sold to me by Rusty at Max's BMW shop.
 
I wonder:
If the bike is parked on the SIDESTAND and leaking out of the right carb, where is the leak coming from? The over flow of the bowl? From the gasket around the bowl? Or where?.............It matters as if on the SIDESTAND, the natural flow of an overflow from let's say a stuck needle valve or the float level set to high CAN go into the sump of the engine itself if let's say the overflow is stopped up. So that is worth checking.

Is the bike running when doing this?

Why are both petcocks open at the same time? Most often, RIDERS, will open only one, and use the second one as a "reserve". This is often for folks who KNOW how to nurse a tank for all it is worth when riding longer distances and need to judge how far they can get till that next fuel stop.
 
Thanks for the tips. I did some research. I chucked up a q-tip in a drill, with a mild abrasive polish, and polished the seats. It seems to be holding for now, if it starts leaking, I’m gonna try the sand paper trick buckeye recommended. I also found buried somewhere in the massive snowbum blah, there is an Amal carb float needle with a viton tip, that fits??? Anyway, thanks again for the replies, best forum ever!!

They seem to be getting along ok.......for now.View attachment 66978
 

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Cleaning the seats with a Q-tip...

It is possible to replace the seats using a tap to cut threads on the inside surface of the brass 'tube' that is basically the float needle seat. Then, a bolt is installed tight into the internally threaded seat, the carburetor body is heated and the bolt together with the seat is withdrawn from the carburetor body. Installing a new seat requires a fitted drift and heating the carburetor / chilling the brass seat tube.
 
Na Cl K9 said:
It is possible to replace the seats using a tap to cut threads on the inside surface of the brass 'tube' that is basically the float needle seat. Then, a bolt is installed tight into the internally threaded seat, the carburetor body is heated and the bolt together with the seat is withdrawn from the carburetor body. Installing a new seat requires a fitted drift and heating the carburetor / chilling the brass seat tube.
Click to expand...

John, I sort of thought they could be changed, but I don’t think I’m there yet. I asked because Amal seats can be changed as well.
 
10drum said:
John, I sort of thought they could be changed, but I don’t think I’m there yet. I asked because Amal seats can be changed as well.
Click to expand...

IMO, you are far better off to simply do the re-seating with the wet-or-dry. It takes a little time, but for me, on a bike that was 37 years old at the time, I spent about 20 minutes on each carb, and 8,000 miles and more than 3 years later, not one drop of leakage!
 
Replacing float needle seats in Bing CV carburetors.

I only mentioned the replacement process because I could not find it discussed in other posts using the search feature. I know the process is easy because a friend borrowed the spare seats I had and did a perfect job first time and he's an airline pilot too! I have a few spare Bing CV carbs for 70's and 80's bikes. None of them need replacement seats so yes, I'm not to that point either. Which is probably why I have not asked him to replace my spare replacement seats yet. I recommend semi-chrome polish on a q-tip with contact by hand only, however, I've used toothpaste on a pencil eraser before so I would have to say that what ever works - It's one of those "fix it or break it" moments (my motto) in everyone's mechanical life :)
 
Na Cl K9 said:
I only mentioned the replacement process because I could not find it discussed in other posts using the search feature. I know the process is easy because a friend borrowed the spare seats I had and did a perfect job first time and he's an airline pilot too! I have a few spare Bing CV carbs for 70's and 80's bikes. None of them need replacement seats so yes, I'm not to that point either. Which is probably why I have not asked him to replace my spare replacement seats yet. I recommend semi-chrome polish on a q-tip with contact by hand only, however, I've used toothpaste on a pencil eraser before so I would have to say that what ever works - It's one of those "fix it or break it" moments (my motto) in everyone's mechanical life :)
Click to expand...

“Fix it or break it”. Yeah, I’ve worked with technicians who had a “patience? I’m gonna beak something”
 
I was told way back when, that there were no changeable "seats" but that they were a part of the body.

That's why I came up with the wet-or-dry on the end of a pencil eraser!
 
Bing will replace the seats

I've sent two sets of CV carbs to Bing for other service and along with that I had them replace the float valve seats. Dressing them as described above probably works just as well, I'm just pointing another alternative.
 
I changed the needle seats on my R100RS carbs this weekend, Bing sold me the new parts.

Simple job per the Bing instructions, turn in the appropriately sized tap into the needle seat, grip the tap in a vice, use a block of wood against the main jet location and tap the carb off of the needle seat.

Took me less than five minutes to do both carbs, no heat required for my CV's
 
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