Pony motor carb questions

DrCharles · Oct 31, 2017

Can someone please tell me if the fuel inlet to my 70D pony motor carb is 1/8" NPT, or if it's a straight thread with a gasket seal (to the flat surface)? Pipe thread doesn't "feel right"..

Previous owners have run a 1/8" NPT pipe nipple in, but now that I'm "upgrading" to an automatic shutoff, its nipple doesn't have long enough threads to tighten fully (and the nipple is seized so hard in the shutoff housing I'm afraid of breaking it during removal). Another option is to carefully tap the housing to 1/4" NPT and install a reducer bushing.

Also, since the original "fuel system" has a tank and a hose to the manual shutoff (no filter at all!) I have added a sediment bowl with a needle valve to the gas tank. I'm thinking of getting rid of the manual shutoff since I will have the automatic one (and the needle valve when the tractor sits for long periods of time). It's just one more thing to leak or gum up...
Opinions?

Rich Duane · Oct 31, 2017

You may want to think again about that automatic shut off. While using the tractor the fuel in the bowl runs down into the SE from bouncing and evaporation meaning you have to open the door hold the button down to reprime all the time. That manual shut off is your friend.
The threads are 1/8 pipe.
Rich

DrCharles · Oct 31, 2017

Thanks for the tip. I looked at the parts list for the 720D and although the auto shutoff started at s/n 14900, the manual valve stayed throughout the entire production run. So I'll plumb my 70D like a 720D, which includes both auto and manual shutoffs!

I will still need to repair those 1/8 NPT threads in the bowl lid though... I think with slow and careful drilling (in a drill press) I can bore it to 7/16" and tap for 1/4" NPT. Although there's always JB Weld

Dan in Ohio told me that pipe plug on the side of the pony (for the auto shutoff's oil pressure line) was fun to get to. Dan was right! It's easy to see but far from easy to put tools on. A vise grip clamped on the end of a 5/16" wrench was the ticket to get it started, then an 8-point 5/16" socket on a universal with several extensions to spin it out. Even more fun to get the inverted flare adapter started - I used the new steel line as a handle while caressing the end with fingertips until it started. Then some time with a fine tooth ratchet and a crow foot adapter... obviously not intended to be worked on with the pony on the tractor!

Pony motor carb questions

DrCharles

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Rich Duane

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DrCharles

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