Aisan F carb rebuild advice (3 Viewers)

[frankenyota]

Read a few different threads about jet sizing but it seems to differ for year models. I have an early Aisan F carb that l am running on my 2F in my 71 FJ40.
I have removed the old jets and found the primary main jet 112
Secondary main jet 200
Slow jets both 50 (saw 0.85mm recommended)
Power valve jet 80
What would be the best combination of jet size for a 2F with a 2 barrel with F Aisan carb with mechanical secondary’s?
Markings on carb are OL12 so 1970, 12 month build.

Also l had this small gasket / stopper missing from on top of the spacer. It had a big flat spot under full acceleration otherwise runs and idles nice but it hasn’t been driven for years so over due for a rebuild.

 

[MDH33]

From memory, I think the recommended sizes for the early 2 barrel are :
112-114 main
180 secondary
50/50 slow
60 power jet


Edit: ^^^^ above I did to my FJ40 when I lived in Colorado at higher elevation. I'm a lot lower elevation now in Iowa. On my current 40, I am running:

120 primary
200 secondary
60/80 slow jets
80 power jet

 

[frankenyota]

I’m on the east coast at sea level, are those sizes something that was recommended to you or trial and error @MDH33?

 

[frankenyota]

Found a F motor manual online and all the jet sizes l have are whats recommended except l should be running the 0.9 power jet instead of the 0.9 which is for high altitude. Still interested to know what's the best combo for performance, would love to hear from the carb gurus @65swb45 @FJ40Jim

http://repairmanual.free.fr/_engine_manual_F.pdf

[/URL]

 

[65swb45]

Just happened to see this. The ping didn’t work because you forgot the @.

The non-US F engine carbs I have rebuilt here have all had 1.20 main jets. And considering that none of the 2F carbs ever had a primary jet smaller than 1.24, I certainly wouldn’t run a 1.12 in your setup.

As for what’s best, YMMV. It can take years to find the best setup for any one vehicle. I was just telling @majdomo yesterday about the day I nailed the float setting on my 45. Three resets on an off-camber river crossing that got it completely dialed in…and nowhere near the factory setting.

To all, if you find this information useful, consider hitting the like button.

 

[frankenyota]

Thanks for the reply, l will see how the 1.12 goes but look at changing it to the bigger primary jet of 1.24 when i get some small drill bits.
Just wanted to know what were the correct jet size as who knows whats been changed over the years.
Playing with the float settings now and the factory spec of 4.1mm seems way too high, looks like some trial and error.
The carb had a flat spot under full acceleration so decided to rebuild it, been a mechanic for long enough but no carb expert.
I changed the link for your name, thanks for the tip.
Matt

 

[frankenyota]

I found the below in the Ih8mud cruiser carb info, so assuming l could go to 1.42 Primary main jet?

Primary and secondary (P&S) venturis should be 28 & 31 mm respectively.
P&S main jets should be 1.20 & 1.80 mm respectively. Older issue had 1.42/2.00. richens primary circuit and leans secondary circuit.
P&S idle jets should be .50 and .80 mm. older issues has .50/.50. richens secondary idle circuit. Primary idle circuit jet diameter increase might benefit low rpm performance.
Emulsion tube / nozzle assembly is not so straightforward. 73/74 issue eliminates a ring of air correction jets at upper portion of brass emulsion tube. This improves main circuit performance at low rpm. Also lower ring of air correction jets have reduced hole size.
This leans mixture at high rpm. Second improvement is addition of second booster venture to secondary throttle bore to smooth transition to two throttle plates open.
Power valve jet is .80 mm for 73/74 issue and .90 mm for older issue

Cruiser Carb Info - Land Cruiser Tech from IH8MUD.com

FJ40 rear suspension 4-link with 1/4 elliptical springs - Land Cruiser Tech from IH8MUD.com

www.ih8mud.com

 

[65swb45]

This information is incorrect. None of the 70-74 F carbs had a primary jet larger than 1.2. The only US spec 2F carb with a primary over 1.36 was post 1980, where it went up to 1.47. ROW carbs were 1.5.

(Edit: I remember now that there was a carburetor in the 75-80 timeframe with a 1.44 main jet. Not sure how I didn’t remember that before, other than the fact that that particular model hasn’t been on my workbench recently. And the ass-backwards 79-80 had a 1.62)


Why are you so focused on bigger jets in a tractor engine. Makes me think once again about @Mark W MIBS syndrome.

 

[frankenyota]

The information came from the link l posted above, just trying to get the most from this carb to suit my 2F tractor motor. I have the later 2F carb but l thought the earlier carb with mechanical secondary’s was a better carb and l like the early airbox as it suits my 71. Happy to learn from the experts