Trying to help a guy recently who had running problems and suspected the carb. We stripped and cleaned it but it was a bit of a rush job, replaced a couple of bits but still the same problem when he got home and tried it. Further investigation revealed that the carb float had a hairline crack so sunk rather than floated flooding the engine. I had heard of this and rebuilt so many carbs but never came across this before personally then last week I came across an extreme example.

I had a similar problem with a refurbished carb I bought from a US supplier. Fortunately I had some other carbs to put together a frankencarb.

Must not be so rare, I also recently opened a floatbowl to look for dirt, and an old mechanic (older than me, so REALLY old) present picked up the float and shook it next to his ear.
Q: "What are you doing ?"
A: "Listening for gas sloshing inside."

Iirc, our esteemed fellow member :worship: 'the hobbler' (Tom) has often mentioned checking the carb float carefully for cracks/splits/pinholes when responding to threads involving poor engine running, carb problems, etc.

Another way of checking for a leaking float is to submerge the float in hot water and check that no bubbles rise - shaking doesn't work if the carb and float have dried out e.g. on a carb that has been in storage for a while.

Small leaks can be fixed with a dab of epoxy adhesive or similar fuel proof sealer - I don't recommend trying to use solder as when you heat the float, the air inside expands and some of it escapes, then as the float cools, a vacuum is created which can cause the float to collapse. (Btdt )

AL.

Toshi,

perhaps after the repair and before it cools you could drill a small hole in the float to let the pressure equalize....

Joe R

Jo
Surely then you would have a float with a hole instead of a crack which would then still fill up with fuel?

...then you could solder the hole up.

tjmra said:

...then you could solder the hole up.

Click to expand...

Then drill a hole in it.

well obviously, either that or create a small crack so you can let the pressure equalize as it cools.

Love the idea of the frankencarb
I will not be repairing this float as one section has no fewer than 5 hairline cracks. From what I remember from my engineering apprenticeship days and metallurgy the cracks are caused by age or stress related issues set up in manufacture with deep drawn brass. I remember the lecturer saying that the problem came to the fore in the early days of large brass shell cases with some unfortunate consequences

Cannot recommend that a cracked/split/holed float is repaired. Any sort of repair will alter the weight (increase it) of the float which may alter the level at which it floats in the float chamber---which could alter the fuel supply into the carb. For what they cost---RENEW

But I think they're saying that any weight increase will be counterbalanced by the loss of weight in making a hole

fiat500 said:

But I think they're saying that any weight increase will be counterbalanced by the loss of weight in making a hole

Click to expand...

could you not add some compressed air so there extra air would counter the increase in weight..
or even Helium?

Bigvtwin996 said:

could you not add some compressed air so there extra air would counter the increase in weight..
or even Helium?

Click to expand...

Compressed air wouldn’t work as air has a weight so more of it = less buoyancy Helium is a good shout though although it does make your voice sound funny

Bigvtwin996 said:

could you not add some compressed air so there extra air would counter the increase in weight..
or even Helium?

Click to expand...

Surely the introduction of helium would contribute to a higher pitched exhaust note and compressed air likely to cause popping on the over run. Have to agree with Tom in that these floats are so cheap to buy but according to Archimedes a minor adjustment to the float fuel cut off tab should compensate for a bit of solder. But then again what did he know about unleaded petrol , it must be much lighter
Peter could be onto something, maybe designing a float that strains the petrol as well!

I'd recommend fitting a little spring to counterbalance the weight of the added solder.

Or could you not plug the hole with cork - cork floats doesn't it?

Some carbs used hollow plastic floats - these can't be soldered.

AL.

Better still, do away with the petrol engine completely and fit a dirty diesel as there will be plenty of engines kicking about in a few years.
Or go really upmarket and convert over to Electric.


No more float issues.


or buy a new float for about £7