Only runs on 1/2 Choke

[The Riot]

Hello All,
I'm sure there is something on this previously but I wasn't able to locate my situation.
I totally rebuilt the engine on my 1972 Cub, and on the first crank after almost 20 years of not running, she fired right up and runs very well, but only with the choke closed to about 1/2, whether at start up or after it is warm. It just won't run without the choke set in that precise spot.
I tried a few adjustments, worked with the main screw on the carb, tried working with the bumper spring on the governor, but nothing I've tried so far makes it any better.
I'm guessing since I'm having to choke it that means that it is either needing more fuel or less air.

The gasket on the carb looks great, I did have to straighten the Carb top but it looks good and flat now.
Could it be the float in the carb, are there som adjustments I should be trying?
Any ideas?

Any thoughts?
Thanks again,

The Riot

[Barnyard]

Remove the metering jet and run a thin copper wire through it and blow it out with carb cleaner.

[The Riot]

It's a brand new metering jet, I totally rebuilt the carb with all new part, but I'm certainly going to pull the jet and make sure it''s clear.

Thanks Barnyard. I'll keep everyone posted on the outcome.

The Riot

[The Riot]

I pulled the metering jet, it's brand new and was nice and clean. I ran a wire in the jet and cleared the ports and the jet with carb cleaner, put everything back together and still doing he same thin. It only runs at all speed, with the choke partially closed.

Any other ideas?

thanks,
The Riot

[RaymondDurban]

It's a brand new metering jet, ...

Where did you purchase the new jet from? Is it an IH part or aftermarket of some sort? Do you have any gages to measure the size of the opening?
If its too small, the engine will starve for fuel and you'll have to fiddle with the choke to keep it running.

[Eugene]

Couple thoughts.

1) Dip the carburetor and give it a through cleaning.
2) You are sucking excess air some place. Gaskets, carburetor, carburetor to manifold? Manifold to block gasket?
3) Fuel level in bowl to low.

[The Riot]

Carb is clean as a whistle, just did a complete cleaning and new kit, all new parts. I'm betting it's the fuel level, will try adjusting the float and try again. Doesn't seem to be air excess air, all new gaskets, carb to manifold nice and tight, manifold to block good too.
If adjusting float and raising fuel level doesn't work, next step will be taking another look at the Metering Jet orifice. It is an aftermarket jet, maybe the hole is too small.

Thanks again,
The Riot

[Glen]

Hi,
Try putting in the original main metering jet, that it had before, and see if it works any better.

[The Riot]

Will do, hope I still have it.......

Will report in tomorrow.

Good night and thanks.

The Riot

[randallc]

Did you check the fuel flow to the carb and through the carb? Where did you get your rebuild kit?

[Don McCombs]

[The Riot]

It's absolutely amazing, I replaced the new jet with the old one and she's running well without any choke. What's confusing is that the old jet has a visably smaller hole then the new one and required a much smaller wire to prob it. It seemed like she was staving for fuel, hense the reason for having to pull the choke, so I would have thought it would have required a larger jet hole.
Go figure......
Well the lesson learned here is "New is not always Better".

Thanks everyone for the assistance and I hope this was helpful to others.

BTW I still plan to post some pics of this on-going total Rebuild Project, she's really looking good, especially now that I know she runs, we did a recalc on the number of years she was down, almost 20. It was my FIL's Cub.

On to the tranny and rear end next.

Take Care,
The Riot

[RaymondDurban]

Good deal, glad you got it going!

[The Riot]

Outstanding sketch of the Carb and measurements. Definately going in my library.

Thanks Don !

N The Riot

[ScottyD'sdad]

It's absolutely amazing, I replaced the new jet with the old one and she's running well without any choke. What's confusing is that the old jet has a visably smaller hole then the new one and required a much smaller wire to prob it. It seemed like she was staving for fuel, hense the reason for having to pull the choke, so I would have thought it would have required a larger jet hole.
Go figure......
Well the lesson learned here is "New is not always Better".

Thanks everyone for the assistance and I hope this was helpful to others.

BTW I still plan to post some pics of this on-going total Rebuild Project, she's really looking good, especially now that I know she runs, we did a recalc on the number of years she was down, almost 20. It was my FIL's Cub.

On to the tranny and rear end next.

Take Care,
The Riot

If the jet opening is mismatched to some of the other internals, it doesn't run correctly.
Ed