Carburetor adjustment process on a desmoged 2f (2 Viewers)

[Slow Poke]

I have a 77 2f that’s been desmoged and I just rebuilt the carburetor. I’m looking through the FSM on performing a basic tune up and wondering about the throttle positioner. It seems to have worked hand in glove with the emissions system that I don’t have. Does it serve a purpose on my truck and how should I set it up?

 

[Pighead]

I got rid of my throttle positioner a long time ago. I don't miss it.

 

[Slow Poke]

So in a desmoged rig it serves no purpose?

 

[Pighead]

So in a desmoged rig it serves no purpose?

I'm not going to claim to know all about the TP. I think I understood it well enough at one time but I've been wrong before, and the TP may have changed some between my '74 and your '77. It's easy enough to test and see what yours does. Take it off and see what happens, put it back on if you think you need it.
I just like my carb as bare-nekkid as possible and dislike vacuum diaphragms on it.

 

[65swb45]

Considering that the throttle positioner releases its position the second the diaphragm has vacuum (engine has started), logic says it can only serve a purpose before and during startup.

Anyone who has had a Landcruiser for any length of time is already familiar with their engine’s particular requirements at start up, virtually none of which require a preset throttle position. My engines all seem to prefer hand throttle over hand choke, and like @Pighead , I have removed the throttle positioners, or at the very least set them so that they don’t interfere with my controls.

If you wanted to create a custom fast-idle setup, you could theoretically build one by utilizing something like an FJ60 AC vacuum switch that you could toggle on, sending vacuum to the TP once you are satisfied that your engine is sufficiently warmed up.

 

[numby]

So in a desmoged rig it serves no purpose?

I still run one but that's just for giggles. I still have the computer under the dash too ('78) but almost no other emissions equipment. The only - and very questionable - benefit is that it holds the throttle cracked open a tiny amount to decrease afterfire on deceleration over a very limited speed range. Like 8 to 15mph or something (can't remember right now). Mines only set to 1200 RPM so it barely does anything in the way I use the vehicle. Most people don't want it so as to maximize engine braking.

 

[mattressking]

Considering that the throttle positioner releases its position the second the diaphragm has vacuum (engine has started), logic says it can only serve a purpose before and during startup.

Anyone who has had a Landcruiser for any length of time is already familiar with their engine’s particular requirements at start up, virtually none of which require a preset throttle position. My engines all seem to prefer hand throttle over hand choke, and like @Pighead , I have removed the throttle positioners, or at the very least set them so that they don’t interfere with my controls.

If you wanted to create a custom fast-idle setup, you could theoretically build one by utilizing something like an FJ60 AC vacuum switch that you could toggle on, sending vacuum to the TP once you are satisfied that your engine is sufficiently warmed up.

Hand throttle vs. choke is a good reference point because the choke kicks the primary butterfly open simultaneously (1.3mm lol)- so that would make sense why you encounter that.

I will say that is why I love the 40/60 series choke breaker and VTV, neat little feature to eliminate the choke dance when actually cold.