Carb Rebuild-Plus

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TallCoolOne58
Posts: 8
Joined: Tue Sep 18, 2018 1:38 pm
Zip Code: 13126

Carb Rebuild-Plus

Postby TallCoolOne58 » Thu Oct 11, 2018 1:29 pm

Since obtaining my '57 Cub this past summer, I have put a lot of effort, spare time (not to mention money) into making it 'right', the best it can be. Missing, damaged, or worn parts-replaced. I approach each system AS a system, and overhaul as necessary, adjusting to specs.

After a complete tune-up and carb overhaul, the tractor started easily, and ran well, but I still wasn't quite satisfied. The exhaust fumes when ran in the garage (doors and windows open of course) would just about make your eyes water, and seemed excessively 'smoky', NOT a blue oil burning smoke, but a dark smoke from what impressed me as excessively rich exhaust, low or high idle. I wiped my finger inside the tailpipe, black sooty carbon deposits, same on spark plugs ( I am running Champion D21's until I get it running to my satisfaction, to minimize fouling, then I will switch to D18Y's).

I sat in the garage pondering this over a cold beer, and decided to order the .030" main jet from TM, and give it a try. Order came today, installed it, and all I can say is WOW. What a difference. Started up immediately, no choke. Warmed up a bit, and ran it at high idle. Probably gained 100-200 rpms top end, ZERO smoke, and only a light smell of exhaust in garage, no choking fumes. I am 100% satisfied now.

Just wanted to share.

Bob McCarty
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Re: Carb Rebuild-Plus

Postby Bob McCarty » Thu Oct 11, 2018 4:47 pm

If you can read the part # on the flat surface above the float chamber, you can find out what the jet size should be. Most of the aftermarket kits contained the same main jet, even if the carb called for one larger or smaller. It's great that you found an easy fix.
"We don't need to think more,
we need to think differently."
-Albert Einstein

TallCoolOne58
Posts: 8
Joined: Tue Sep 18, 2018 1:38 pm
Zip Code: 13126

Re: Carb Rebuild-Plus

Postby TallCoolOne58 » Fri Oct 12, 2018 5:43 am

I looked high and low on the carb throttle body for a stamped part number while rebuilding. Naturally, no idea what PO's in the past did what to what. The fuel inlet strainer screen was missing, float level was 1-1/2", float drop was 1/4", and the throttle body to bowl was double gasketed. Tweaked to 1-13/32" and 3/16" respectively, after a thorough disassembly and cleaning, and float axle, needle and seat w/gasket replacement. Naturally, a 'freshened' air tight carb is going to run richer than it had been, from prior 'adjustments' to compensate for wear and warpage.

I used to rebuild a lot of carbs back in the day as side jobs for an extra buck. This was one of the simplest carbs I've had the pleasure of working on in quite some time, idle tube and main jet overlap @ midrange throttle, so no accelerator pump required. Definitely responded well to surgery. I too am happy that I (educated) guessed right on the main jet orifice size needed. A pleasure to start, run and operate now.

Thanks very much for the reply.

TallCoolOne58
Posts: 8
Joined: Tue Sep 18, 2018 1:38 pm
Zip Code: 13126

Re: Carb Rebuild-Plus

Postby TallCoolOne58 » Fri Oct 12, 2018 5:49 am

Whoops, meant idle tube and discharge nozzle overlap @ midrange throttle. I need my 2nd cup of coffee!

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Glen
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Tractors Owned: 1956 Farmall Cub with Fast Hitch, F-11 plow, Disc, Cultivator, Cub-22 mower
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Location: Wa.

Re: Carb Rebuild-Plus

Postby Glen » Fri Oct 12, 2018 5:54 pm

Hi,
Below is a page from the Cub service manual showing different part numbers of carburetors, and specs for them.
IH changed to the 2nd carb in the list at Cub serial number 192113, I think, which was late 1955. That is when several changes were made, Raymond Durban's database shows that also.

IH started using the Zenith carb in mid 1975, so there were many Cubs with the IH carb originally. :)

http://www.farmallcub.info/manuals/gss- ... 002-02.jpg

TallCoolOne58
Posts: 8
Joined: Tue Sep 18, 2018 1:38 pm
Zip Code: 13126

Re: Carb Rebuild-Plus

Postby TallCoolOne58 » Sat Oct 13, 2018 5:54 am

Hello.

Much appreciate your effort posting the info, I do have the GSS-1411 Service Manual though, which I love to read through. I do a lot of research before making a move.

Makes sense the carbs were calibrated 'leaner' as the years went by, improved gasoline quality etc.

I'm really liking the new .030" main jet in my carb. Much improved overall performance, with the added bonus of (i'm sure) a bit of improvement in fuel economy, and definitely runs 'greener'!

Thanks for the reply.


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