300 u carburetor needle valve

[realolman]

I bought a 300 u about 12 years ago... I used it to plow snow and occasional jobs around the house ..

Yesterday I was installing a carburetor rebuild kit and the needle valve screw for the main jet wasn't right at all. That ended up with me deciding that the needle valve screw that was already in there wasn't right either... it wouldn't go within a 1/4" of completely closing off the gas to the jet...

Now I know you wouldn't normally close off the jet for operation, but it seems to me it should be nearly there when adjusted right or the valve wouldn't do much.

I ended up grinding / filing off about 1/4" of threads so that it would go in far enough

You can imagine what that looks like... not nearly as nice as it should to seal in the packing gland nut



this is the carburetor

this is the needle screw in the packing gland... I always wondered why it was boogered up so much

this is the needle valve that was in the carb and the one that came in the rebuild kit

[/img:6dd2edc1b2]

You can see where I filed the threads off to get it to go in far enough...

The thing has always started super easy, seemed to run OK, but it seemed like the governor didn't do anything. I have been fooling with the governor and trying to adjust the carb... nothing has really made any difference ... that's why I tried the rebuild kit...

I think if I had the proper screw it would probably make things straighten right up. I imagine this one would work, but I'm afraid it would probably leak... I wish I had a lathe, but it might be hard to chuck it in good enough anyway.

I would like to get a correct needle screw but I haven't been able to find one... any help??? thanks

 

[wore out]

Is it possible you are missing the "jet", Key #47, that installs deep down inside the carb?

Looks like some versions used it and others didn't.

 

[realolman]

(quoted from post at 11:28:12 03/07/21)

Is it possible you are missing the "jet", Key #47, that installs deep down inside the carb?

Looks like some versions used it and others didn't.

Thanks for your reply... anything is possible with a 60 year old tractor... I know there was nothing like that in there when I took it apart, but I also know the needle valve screw needs to be longer than what I had.

I will look into that, but in the meantime, I think the part I filed will not interfere with the sealing of the packing and I know for a fact that it goes in far enough now, so maybe I will just let it go as it is.

but thank you for your reply... I what you posted is certainly possible... I don't know

 

[pete 23]

Have to love those kits. What kit makers don't seem to realize is there are
two different lengths AND taper on the tip of the main fuel adjustment screw.
Also, some new packings are just too long so cutting off a portion will
usually get so you can screw the needle all the way in to bottom on main jet.

Then, the idle mixture screw gets subbed for air adjustment idle screw.
Throw in the wrong main metering nozzle and you got a mess.

I seldom use kits. Get separate parts I want which now days isn't always easy
but McDonalds has quite a large inventory. Actually, don't really work on
them anymore except special occasions.