Zenith carburetor

Thu Nov 11, 2010 8:11 pm

I have a 1973 model Lo Boy 154 that was obviously retrofitted with a Zenith carburetor. I did not have any real carburetor problems but decided to disassemble it and give it a good cleaning. On disassembly I noticed the small coil spring that fits on the float axle/rod. Checking out various web sites for Zentih parts diagram I could find no picture that showed this spring installed. On furthur investigation it appears Zenith Carbs that fit Lo Boys had some with the coil spring and others without. I decided not to install the spring on reassembly but the tractor would only run a few minutes and then quit. Apparently the valve needle was sticking closed. After disassembling carburetor, I reinstalled the spring but was not 100% sure if it was installed correctly. I haven't had enough running time since to be sure it is installed right. Does anyone haveexperience in this regard. What exactly is the function of this spring? It looks too small to be effective but it must have been put on the float axle for a reason.

Re: Zenith carburetor

Thu Nov 11, 2010 9:30 pm

Edit: 68-7 Carb. Picture in the back of Wisconsin instruction and parts list for the TH,THD, TJD. Back of the book. This spring fits on the float anchor/axle pin and is used to help lift or stabelize the float.

Spring fits with the ends of the coil up.

Re: Zenith carburetor

Fri Nov 12, 2010 8:52 am

I've worked on Cub Zenith's with this type of spring(other versions too), used to pull the needle down as the float goes down'
float spring.jpg

(pic borrowed from public internet search)click to enlarge

but never ran across the spring on the axle pin type installed on a cub. Other brands use it, but usually then the float has fingers that grab the needle to pull down.

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Last edited by Rick Prentice on Fri Nov 12, 2010 4:46 pm, edited 1 time in total.

Re: Zenith carburetor

Fri Nov 12, 2010 10:30 am

I had to edit my original post on this topic - cause I didn't read it thoroughly. The spring on the float axle was used on the Wisconsin engine, also the Gravely L (hope the L is correct) and probably several other applications.

Zenith used the clip Rick described. Also, one more, a spring with what looks like a nail that fits inside the needle valve.

Tried to find an exploded view of the carb on the web. Couldn't. The paper Wisconsin manuals have appendices copied directly from their parts suppliers for the carbs and magnetos. The web manuals do not have the appendices.

Re: Zenith carburetor

Fri Nov 12, 2010 3:24 pm

Can everyone else see Rick's link?

Re: Zenith carburetor

Fri Nov 12, 2010 3:51 pm



Re: Zenith carburetor

Fri Nov 12, 2010 4:41 pm

You guys musta broke it :shock: I looked at it all day, now I can't see it either.


Re: Zenith carburetor

Fri Nov 12, 2010 4:47 pm

Try it now :D

Re: Zenith carburetor

Fri Nov 12, 2010 5:00 pm

I must have installed the coil spring correctly because today I mowed at nealy full power and had no problems. I'm not quite sure what Eugene meant by having the ends of the coil up. I installed it with one end of the coil over the float plate and the other under. In order to do this I had to rotate the coil in order that it would put pressure on the float plate. This took a bit of doing since my fingers are large and the coil spring is so small. Still I have to wonder how such a small weak spring can have much effect on the float itself. THis method is certainly different from the springs that hook onto the float valve like I have seen in so many other applications. BTW, thanks for all of your replies.

Re: Zenith carburetor

Fri Nov 12, 2010 5:18 pm

I see it! I see it!

Re: Zenith carburetor

Sun Nov 14, 2010 7:33 pm

Spring ends up was from the picture in the Zenith annex.

My guess, the small spring on the float axle is to help reduce the float bounce/vibration in the fuel bowl on single cylinder engines.

If you have the manufacturing number from the carb you may be able to tell the original application.
http://www.asecc.com/data/wisconsin-zen ... retor.html

I have a VH4 with model 68-7 Zenith carb and it does not use the axle spring.

The THD Wisonsin engine, 53.9" displacement, develops 13.1 hp at 2000 rpms. The carb with adjustable main and idle jets would be a good match for the C-60 engine.