BMC 4/25 carb issue

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patsprice
Posts: 2
Joined: Sat Nov 17, 2018 12:12 am
United States of America

Re: BMC 4/25 carb issue

Post by patsprice » Mon Dec 17, 2018 2:56 pm

Similar flooding issues, in my case too much standing, rust, condensation, fuel filter literally separated and became a pass-through and I doubt the needle and seat stood a chance.

Tried getting a needle and seat, cannot find the part individually. Does anyone have the part number? And is there a generic equivalent?

So I stripped the carb as far as I could, soaked the parts in cleaner, placed the carb and bowl in dishwasher and ran a full cycle, did a wonderful job, discovered orifices I could not see were there. Made my own gaskets from cardboard for the (emulsion?) interface where it screws to the bowl, and 1/16 cork for the float bowl and where the emulsion interface meets the venturi, whatever that is called; and started with heavy duty cable ties to pull it back into shape, ended up using 3" and 3.5" hose clamps to pull the carb (gently) back into shape, relying on the "give" in the cork, to overcome the metal distortion of many years.

Now to put it back on the tractor and see if the needle and seat is any good, after being cleaned and cleaned and cleaned.

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CNR
Posts: 20
Joined: Fri Oct 05, 2018 11:34 pm
United States of America

Re: BMC 4/25 carb issue

Post by CNR » Mon Dec 17, 2018 7:10 pm

Let me know how in runs after the carb cleaning. There is a company in Wisconsin at sells alot of parts for the gas engines including carb rebuild kits.
Mine was the pickup pump. It was a diesel pump not a gas one. Diesel uses 9 psi and gas is about 3. The pump was pumping too much fuel and the fuel over flowed into the carb and flooded the engine out.
I put a fuel pressure regulator in the fuel line use before the carb. I bought an adjustable one at a local auto parts store for $30. Set it at 3 psi and it runs good now..

patsprice
Posts: 2
Joined: Sat Nov 17, 2018 12:12 am
United States of America

Re: BMC 4/25 carb issue

Post by patsprice » Tue Dec 18, 2018 12:06 am

Re-fitted the carb, hooked up choke, governor and fuel and it started right up. So far, so good although it is early days. Needle and seat seem to be holding and it is running smoothly and idling smoothly at low RPM. Previously it was always racing like it was relying on the fast idle adjustment (which I dialled way back) and now it can idle really slowly and still smoothly.

What a difference.

I think there was a confluence of factors, dirty fuel and lines, leaky cork gaskets on the glass bowls, many blocked orifices in the carb, false air being sucked in everywhere (leaking like a sieve), distorted carb metal, poorly made gaskets, pretty much soup to nuts it needed TLC, everywhere.

Now to tackle steering play...

Danny Chambers
Posts: 1
Joined: Sun Nov 25, 2018 10:01 pm
United States of America

Re: BMC 4/25 carb issue

Post by Danny Chambers » Wed Dec 19, 2018 2:08 am

I have the same problem, my 4/25 long, has only 600 hours. So everything is goo! I've been through the carb, fuel pump, and electrical, is great. But I'm using the boat tank out of my wife's flat boat, cause my fuel line is stopped up. I get fuel through the glass bowls, just not through the line. And my clutch is frozen up. I would appreciate any information on this lil'beast. Tyvm
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CNR
Posts: 20
Joined: Fri Oct 05, 2018 11:34 pm
United States of America

Re: BMC 4/25 carb issue

Post by CNR » Wed Dec 19, 2018 4:09 am

Is the fuel line metal of rubber?

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