The Home Machinist!

NP317 wrote: ↑Thu Feb 25, 2021 6:39 pm "...leaks when engine is cracked..."
What is cracked? The cylinder? The throttle? Clarity please.
RussN

The OP may correct me if I'm wrong, but I believe he meant to write "cranked". As in "spun" or "turned over".
John

There is nothing problematic with those old Briggs carbs. Super simple and reliable. You say it is rebuilt? Doesn't look like something that was done in recent times, hardware paint/gaskets don't appear to be disturbed. Drop the bowl and clean it. Remove the float and needle. Gently close the main mixture screw to find it's setting (count the turns, typical 1 1/4 turns) and then remove it. Blow some air thru the jet. Put the mixture screw back in and back off to the original setting. Clean the float needle, blow some air thru the needle seat. Put the needle and float back. Float should be level when needle is seated. Easiest to see with the carb upside down. Leave the air cleaner off. No fuel. Turn the engine over with your palm over the carb throat. You should feel good suction. If not you have an engine valve problem.
Is this motor still set up as a make n break? The original fuel mixer (carb) had a poppet valve that isolated it when the engine was spinning over but not firing. I wonder if that is incorporated into the adapter block bolted to the head...
Or has the engine been converted to constant ignition?
Even with gas puking from the carb it should run unless your not getting any vacuum. Hand test will tell you that.
You may have crud keeping an engine valve from seating.
There are plenty of people that mess with these engines. Lots of info out there. Proper mixers are out there too. I don't know your engine displacement but I'm sure it's quite larger than what that Carb is meant for. May well have to have the mixture a bit rich. Generally they were started cold on gasoline, the mixer has a hatch and bowl to fill with gas, then it ran on kerosene.
Whats the backstory on your motor? New to you? Barn find? Sure nice starting with something not found in a field!
It really shouldn't take much tinkering to get it running. Pretty basic and bullet proof.

Hi Bob, others text me the engine did run with the present setup although I have never seen it, I did remove the the carb and rebuild it, I also installed a vacuum gauge onto the intake port to prove there was suction, valves appear to be fine, no poppet valve in block adapter.
I wonder if the fuel tank being higher than the carb is creating a problem, I may try lowering it.
Thanks for the input, it may be awhile before I get back to it.
ALL LIVES MATTER!
Geo

If the fuel tank is less than 3ft above the carb lowering will make no difference. Float level may be to high.
What exactly did you do to rebuild the carb? How did you hook up a vacuum gauge?
Using a squirt oil can filled with gas you should easily be able to keep it running with small squirts into the carb, air filter removed.

Hi , for the vacuum gauge I threaded the port of the gauge into a plate that was fitted over the intake port of the engine , in place of the carb. been so long since I rebuilt the carb I can’t remember what I did, I would imagine I purchased a kit, I have been checking my records to see what I can find.
Here is the only pic that I can upload.


ALL LIVES MATTER!
Geo

Hi Bob, just curious if you have ever check this B&S Flo Jet carb out on line, it appears to have a leaking problem with the emulsion tube.
ALL LIVES MATTER!
Geo

It leaks when it’s cranked,

Hi, I have rebuilt the carb, again, still some fuel in the carb throat, seems to kick back when I turn it over, some times, it has a Bosch magneto which is producing a good spark, could it be a timing issue, main jet open to much ? Starting procedure I have used is choke closed throttle wide open and turn it over with the crank.

On the Fairmont Railcar 2-cycle gas engines I have rebuilt and operated, your kick back symptom would be solved by moving the manual timing lever more retarded.
Normal procedure for starting, then advanced once running.
Does your engine have such timing adjustment?
RussN

If cracked = cranked then perhaps you have a leaky intake valve that is blowing back.

Careful about having the air filter off under these conditions...could blow back and start a fire...which is not something you want to have happen with face looking down..

Or perhaps the float setting is wrong. If it is an old carb and you have been putting gas with ethanol in it...the floats have a habit of getting heavy...and while the static setting is correct...the floating height is different and you get too much fuel

Had this happen to a BMW motorcycle...required float alterations before it was all over with. The floats were made of some foam material that did not like alcohol.

Does the float look like it is made from some natural material or is it a brass solder up type of float?

Hi All, something I just noticed was that the intake valve never seems to move, I would think it should open on the intake stroke.

worn cam shaft or loose lifter....????