Carbs keep flooding into main throat.

With the bike tilted on the stand half the gas in the bowl is higher and half is lower and in the middle it doesn't change.

Anyway...you have bad parts or bad assembly, or bad measurement technique/tools.
 
The fuel vent is an opening that allows fuel to replace the air in the float bowl. Not sure where it opens to in the BS38 (assuming that is the ones you're using here...), I think somewhere inside the venturi opening (throat) towards the top. I would imagine if that's clogged you'd have more to worry about.

Look, not trying to confuse you. You really need to take a good look at those float valves. Testing with air is not good enough, you cannot build the same kind of pressure as a liquid. That's why hydraulic brakes have fluid not air. Furthermore gas has a low surface tension, meaning it will go through (very) small openings that would not let water through for example.

You chasing the needle jet issue is a red herring IMO, bad o-ring or needle jet (these rarely do go bad actually but my experience is limited there) cannot be why gas creeps up.

Whatever it is I hope you figure it out quick.
 
I mean the needle jet itself. The o-rings yes they do go bad, but it'll mostly only make the bike run rich.

BTW are those BS38? If so I think I have o-rings somewhere let me know I'll send you 2 or 3.
 
I'll look, I think I do but will confirm when I get home. PM me your address I'll put a few in an envelope.
 
Take a step back..........Stop working and thinking you know what the problem is, and don't work on your carbs for at least a week.

Take the time to let your mind relax and over the next few days things will come to you but don't go back to work on them.

Couldn't get better people than Grizld1 or RG for advice and help.

Thinking logically .........

1; Liquid finds its own level.

2; If the source is higher than the reservoir then the reservoir will overflow unless there is a shut off valve of some kind

3; If the fluid is overflowing the reservoir then any shut off system has to be checked for problems.
 

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Smithers, did the O-rings fix your problem?

I was searching for an answer to this problem and when I came across this post, it was like I wrote it. I am having the exact same issue that you are.
I have read the Carb guide, replaced the float valves, replaced the floats, set the float height correctly and the carbs still pour gas out of the venturi or "throat" of the carb. They flood into the venturi when they are on the bench (level) and when they are on the bike.

I can get them to stop flooding if I set the float height to something really high like 30mm but then the bike will only run for a second. I am going to start backing that number down to see if I can get the bike to run and the carbs not to flood but I really would like to set it in spec and have them work.

Let me know how the o rings worked for you, but based on my understanding of how the carbs work I dont see them fixing the issue.
 
6x5s0 said:
Smithers, did the O-rings fix your problem?



I can get them to stop flooding if I set the float height to something really high like 30mm but then the bike will only run for a second. I am going to start backing that number down to see if I can get the bike to run and the carbs not to flood but I really would like to set it in spec and have them work.
Click to expand...

I think you have probably found the answer right there in the float height setting.

The fact that you can consistantly cure the leaking problem by setting your floats at 30mm proves that there is nothing wrong with the needle valves. This problem looks to be related to the float height setting.

Before I read your last post I read through the entire thread together with the links and my instinct was that either the float height setting was somehow wrong or there was a fracture or hole or leak somewhere in the fuel bowl .

I was going to ask if the needle valve had the correct spring fitted and if when you measured the float height you were measuring the 25.5mm with the needle valve pin spring compressed or uncompressed ? Obviously if the spring is compressed and the pin down it will give you a false reading.
 
When I took the measurement the spring was uncompressed, which i believe is correct.
I'm going to start lowering the float height tonight. hopefully i can find a sweet spot somewhere between 25 and 30 mm where the bike runs and the carbs don't overflow.
 
peanut said:
The fact that you can consistantly cure the leaking problem by setting your floats at 30mm proves that there is nothing wrong with the needle valves. This problem looks to be related to the float height setting.
Click to expand...

Not really. Setting the floats farther away from the deck puts more pressure on the needle which should give better sealing. If it doesn't work with the floats set to spec, then something is wrong - you can't get around that. Plus float height (fuel level in bowl) helps determine fuel/air mix, not just the jets and fuel screws. Figure out what's going on or suffer the consequences...
 
Is there a good way to lap the needle valve seat? They are brand new but maybe they aren't quite sealing. They seem to seal when I blow air into the fuel lines but i realize that isn't a great test.
I would just replace them but they end up being about 30 bucks with shipping and everything. Not to mention the carbs did this with the old needle valves installed also.
 

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