2F Secondary not opening (1 Viewer)

[gmac]

I asked that question because my Toyota carb mechanic told me it can? I mentioned it after my rebuild that the paper clip test revealed that the diaphragm was not pulling? After watching @Pin_Head video it seems that the diaphragm is essential to the secondary opening.


devo

@pithicus on his comment above (#13), mentioned that he mechanicalized it, but I can tell how from the photo.

 

[pithicus]

Sorry the phone photo is terrible. It.s very simple, just a self tapper screw next to the spring. I had to drill 1/8 hole in the lever mechanism for the screw. I will try and get a better pic if you want?

Warning, not for the purists, but it does work .

Also this carb is from a 3f auto, so it's probably different to the older 2f carbs regarding the throttle cable/mechanism .

I have a late 70's fj40 carb in the shed. Will look at it tomorrow to see how to mod it. That might be more helpful, and hopefully post pics tomorrow.

Here's a bit better pic of the screw. It presses on the lever that opens the secondary at about 1/3 throttle.

Here is with the screw removed. It's 1/8 inch hole drilled through just above the cable lug hole.

The vac pod is removed and a wire attached to keep the secondary spring tension correct.

 

[Pin_Head]

Can the secondary open (fully) without assistance from the diaphragm?


devo

No. At least not the ones with a vacuum actuated secondary from ‘75 and up. Earlier carbs had a mechanical only secondary.

 

[devo]

So, can you modify the ‘75 and up to mechanically activate the secondary? Would it be an easy and reliable means to bypass the vacuum that is giving countless folks trouble?



devo

 

[pithicus]

So, can you modify the ‘75 and up to mechanically activate the secondary?

You can do what I did, and there's probably other/better ways to do it. I did mine in a hurry coz I had no quick access to a new diaphragm , but I ended up liking the mechanical mod. I can feel when the secondary opens with my foot [extra spring pressure]. I don't know what effect the mod has on performance/economy but it seems to work ok.

Forgot to add, the vac hole has to be plugged after diaphragm pot is removed.

 

[devo]

@pithicus can show us photos and better detail of the mod?




devo

 

[Pin_Head]

If you want a mechanical secondary, you could just get an early Aisan carb or a Weber 32-36. You don’t want something that may turn out to have an unreliable throttle control as it could be a safety issue.

 

[pithicus]

@devo I just did a mod on a late 70's fj40 carb. Have a look at attached and it should give you a bit of an idea, assuming your carb is the same.
Let us know if you give it a go.
Cheers

Will need a circlip on the bottom [below pic]

 

[devo]

Thanks @pithicus



devo