Construction and other equipment - Allis Forklift Zenith carb question

Allis Forklift Zenith carb question

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Category: Allis Chalmers
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=200289
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Topic: Allis Forklift Zenith carb question

Posted By: alRCRVRP
Subject: Allis Forklift Zenith carb question
Date Posted: 13 Mar 2024 at 7:42pm

I have a Allis Chalmers fork lift model FP-40-24 with an overhead valve AC engine.

The carb on it is a Zenith.

Numbers on carb are as follows.

6-95

13153

4515463

It runs a bit rough on acceleration. I have replaced the plugs, points and condensor and adjusted the horizontal idle screw on the side of the carb so it idles well. Adjusted the timing by ear, almost impossible to get a timing light in there.

It still stumbles a little on acceleration, not bad but noticable.

I has thought there was a high speed adjustable jet coming out at an angle on the bottom of the carb bowl but there is only a hex headed plug there. Another hex head pointing straight down.

Is this a carb with a fixed high speed jet?

Any suggestions for me?

Replies:

Posted By: Eric B
Date Posted: 14 Mar 2024 at 6:41pm

Yes, some of the older carb applications had a fixed main jet. I have one on my old Allis B tractor. It works great, you may have to clean the carb if it seems to run lean at higher speeds. I feel that the fixed jet is slightly on the generous side, better that way for me than running lean.

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Currently- WD,WC,3WF's,2 D14's B. Previously- I 600,TL745,200,FL9,FR12,H3,816 LBH. Earth has no sorrow that Heaven cannot heal!

Posted By: Braswell
Date Posted: 15 Mar 2024 at 6:03am

Check the spark… the (secondary ignition spark)..
If you hold the coil wire close to a ground and spin the engine. The spark should be blue, fat, 1” long. If you have graphite core spark plug wires change them to copper core, if you already have copper core wires and still have a weak spark ( thin yellow) then look at a new coil. If you still have breaker points look into Pertronix Ignitor kit and upgrade the ignition. It’s $100 not counting the coil.

Posted By: alRCRVRP
Date Posted: 15 Mar 2024 at 8:42am

Thank you for the replies, I'll check it out further.

Posted By: PaulB
Date Posted: 16 Mar 2024 at 6:59am

As with most all older carburetors when trying to run them on "todays' gasoline they need to be richer. Almost all of todays gasoline is "oxygenated" in some manner to comply with EPA regulations. Try drilling the main jet a little bit bigger with a number drill, find a size that just fits and go 1 or 2 sizes bigger until it runs better. Many Zeniths can be retrofitted with an adjustable needle in place of the main jet access plug, that allows you to go a little larger than really needed and lean it back with the needle, to get the mixture precise. I do that with all of the Zenith Carburetors I work on.

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If it was fun to pull in LOW gear, I could have a John Deere.
Real pullers don't have speed limits.
If you can't make it GO... make it SHINY

Posted By: alRCRVRP
Date Posted: 16 Mar 2024 at 8:19am

And thank you for that reply. It does have the fixed jet. I decided yesterday to rebuild the carb since it probably has not been for 50? years. And it does almost seem to have the symptoms of a soggy or leaky float. I'll include changing to the adjustable jet. Do you recommend an online store that has good kits at a reasonable price.