Allis Forklift Zenith carb question

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   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?

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alRCRVRP Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 13 Mar 2024 Location: Wisconsin Points: 5	Post Options Post Reply Quote alRCRVRP Report Post Thanks(0) Quote Reply Topic: Allis Forklift Zenith carb question 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?

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Eric B Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 09 Feb 2012 Location: British Columbi Points: 961	Post Options Post Reply Quote Eric B Report Post Thanks(0) Quote Reply 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.
	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!

Braswell Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 14 Feb 2024 Location: North Carolina Points: 30	Post Options Post Reply Quote Braswell Report Post Thanks(0) Quote Reply 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.

alRCRVRP Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 13 Mar 2024 Location: Wisconsin Points: 5	Post Options Post Reply Quote alRCRVRP Report Post Thanks(0) Quote Reply Posted: 15 Mar 2024 at 8:42am
	Thank you for the replies, I'll check it out further.

PaulB Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 12 Sep 2009 Location: Rocky Ridge Md Points: 4906	Post Options Post Reply Quote PaulB Report Post Thanks(0) Quote Reply 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.
	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

alRCRVRP Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 13 Mar 2024 Location: Wisconsin Points: 5	Post Options Post Reply Quote alRCRVRP Report Post Thanks(0) Quote Reply 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.