Reversing Throttle and Choke Linkage on Zenith Carb

T_MAC · Jan 20, 2014

Hi,
I have a John Deere Model 40 Tricycle. My dad ordered a Zenith carb from Yesterday's tractors years ago. It has been sitting new in the box and unused. To install it, I need to reverse the linkage for the throttle and choke. Anybody done this before? Any tips? Thanks in advance. Great site here.

Bob Bancroft · Jan 20, 2014

If I understand correctly, you have come up against a major problem with "replacement" carb's.
I had to reconfigure a throttle shaft once. Someone else had replaced with the wrong one. There are so many variations on angle, and length of the arm. It would have been nice to have seen the original!
Have you talked to the parts people here to see if you could get the correct one?
What's the status of the original?
Since both shafts are wrong, there may be more wrong inside also.

Steve@Advance · Jan 20, 2014

I've taken them out before, but never tried to reverse one. Possible it could be done, but look everything over carefully first.

Usually the screws are braded over so they won't come out. You'll have to grind the braded end off before CAREFULLY removing them, and then find new screws so you can rebrad them. Usually they are brass and just love to twist off.

Good luck!

T_MAC · Jan 20, 2014

Thanks guys. I spoke to brad at YT parts. He indicated the carb is designed so that the linkage can be reversed. He"s going to send some instructions. My big concern is getting the staked screws out without damage plus access is really limited to restate new ones...I"ll let you know how it goes.

Bob Bancroft · Jan 20, 2014

I don't know about now, but it used to be common to have lock washers on those little screws. A drop of thread locker on them would also be a good idea. I'd be hesitant to try to "stake" those screws myself as bending the throttle shaft would be easy. I always tightened them VERY tight. I've even busted half a screw head off doing so!
Be aware that a throttle plate only goes in correctly one way. The edges are tapered, and the holes are offset a tiny bit. On installation, the idle stop screw on the shaft/arm is backed out so it doesn't touch- the plate screws snugged so the plate can still be moved- then "tapped" on so the plate is centered and seated in the throat- then while holding it there with tension on the shaft- tighten the screws. You will feel the shaft turn slightly as the plate is tightened to the shaft. Turn the idle stop screw in until the throttle plate just opens. Then you have a good starting point for running the engine.

Mike M · Jan 21, 2014

I had an aftermarket Zenith on my M when I got it. It ran fine, but the air inlet size didn't match up to the air cleaner outlet size and it is a VERY tight fit where only a factory hose can go in there right. I opted to find a MS carb. like the original so it fit right and would not suck in dirt ! I ended up with one from a model 40 and all has been well.
Just something else to check.

Bob · Jan 22, 2014

"My big concern is getting the staked screws out"

Grind the staked area off with a Dremel tool, get things switched around, then re-install the screws with a tiny bit of LocTite.

T_MAC · Feb 3, 2014

Thanks to all...feel pretty silly after I looked at things again. All I really had to do was move the choke linkage 180 degrees and get a different choke cable...I'm not a rookie but feel like one now!
I did run into the air inlet size issue Mike mentioned. I worked around it...I had a piece of new filler neck flex pipe and got lucky. Anyway thanks for the advice...it is much appreciated.

Reversing Throttle and Choke Linkage on Zenith Carb

T_MAC

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Bob Bancroft

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Steve@Advance

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T_MAC

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Bob Bancroft

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Mike M

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Bob

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T_MAC

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