WO carb throttle shaft

[Carls_jeep]

I am rebuilding my spare WO carb and I need a new throttle shaft. Does anyone know if there are new ones available?

[Doug]

Yes there are. �There are carter carb specialist stores that sell parts or fully restore. �However, are you sure that it is the shaft that is worn and not the body. �The reason I ask is because when they professionally rebuild the carbs, they usually install bushings, being careful not to bore all the way through the body, to tighten up the throttle shaft. �I thought it was the body holes and not the actual shaft that gets worn. �Do you know for sure which is your case. � Usually the intallation of the bushings is left to someone with special experience in their repair.

This company might have parts   http://www.carburetor.ca/

[Carls_jeep]

  Yes, both the shaft and bore are worn excessively. I have no problem boring and bushing the body and I can make a new shaft. If I can buy a shaft at a reasonable price I will do that but I suspect they are over priced. The body is case iron and the shaft is brass and normally the brass wears faster but alas, the shaft is chrome plated and hence the body wore more than the shaft.

I will call that company for a shaft price Monday.

An unworn area of the shaft is .310" by the throttle linkage arm and the other end by the removable arm with the ball is .305" at the smallest area. The bores in the body are .316" at the throttle lever end and .320" at the removable lever end. I suspect this carb was used with a governor because the governors tend to surge/hunt a lot and that would wear the shaft more than a foot throttle.

Since the shaft is near .312" which is 5/16" I will assume the body standard bore was .312" giving .002" for working clearance.

I have several options.

1- make an oversize shaft and bore the body to fit the shaft. Possibly the easiest way to fix it.

2- bore the body and bush it and buy a new shaft.

3- bore the body, bush it and make a new shaft.

 :-? What is the theory of not boring all the way through for the bushing?

[Doug]

I am not sure about not boring all the way through but if I am remember it was something like this.   The inside of the body is a radius.  If you bore all the way through and then have the flat bushing pushed in, it will protrude slightly into the body opening.  Something like that.   All I really remember is reading in several different places that the installation of the bushings was not for novices and that you have to be careful not to bore all the way through.    It was hard for me to image that the little surface area of a bushing that would protrude could disrupt the air flow enough to matter.  However, all the articles about rebushing a carter wo throttle body seem to mention not boring all the way through when bushing.  Never done it myself.  

[Carls_jeep]

I can see where the protrusion would not be good and if pushed flush with the throttle plate there would be four gaps at the bushing end that would cause problems closing the throttle off to set idle.

It wouldn't be hard to use a counterbore cutter to bore it out and make a bushing to fit and locktite the bushing in. That is probably the easiest way considering it would be tricky to dress the end of the bushing in the bore, not impossible, just tricky.

I'll think on it, uhh, I mean ruminate on it.

[Doug]

Carlsjeep, How you said is how the articles I have read say to do it.  I have no idea how to accomplish it or what tools or special bits or special touch would be required to do it.  How would you counterbore it and make sure you do not go all the way through the body.  Just curious to learn how things are done.

[Carls_jeep]

First you would have to mount it on the mill table so the shaft bore is perpendicular to the table. Then you would have to indicate the bore in with the mill spindle. Then you would establish the depth you need to bore it and then set the quill stop with the cutter in place. Then you counterbore it. The bushing would have to be machined to fit the resulting bore and it may be different for each side.

Counterbore cutters seldom cut the same size hole, they are not that precision of a cutter as they tend to runout some just as a drill bit does.

Doing the job with a boring head would produce a much closer bore but with much more work.

It's not hard, it just takes a lot of time to do right. The more I think about it and how thin the boss is where the shaft goes in I believe I will drill and/or ream the shaft bore and make an oversize shaft. The more I look at and think about it that is looking to be the easiest for me. Others may have a different view on it.

Also, a plain brass shaft running in a cast iron bore will last for a very long time. The chrome plated shaft would wear the cast iron faster. Also, I can make the running fit much closer than original. A shaft that small does not need .002" running fit. A .0005" to .001" would be more than enough and a slip fit to start with would be perfect as it would wear in nicely.

Any air that can get in through the throttle shaft can cause a surge issue and is hard to set a steady idle with. Some carbs have an O ring or seal on both sides of the throttle shaft and I have considered that but that is not cost effective here.

Carl, remember, it's a Jeep, not a pocket watch so don't get carried away with perfection.  

[Carls_jeep]

I contacted the carb company and they don't have a throttle shaft. If they do they only use them in house. If they rebuild carbs I don't see how they could do it with a worn shaft so I hope anyone getting a rebuilt carb from them gets a new throttle shaft.

Actually, boring the hole out and making a new shaft is better than rebushing the holes and using a replacement shaft anyway.