Wanted- WWII Carter WO Throttle Shaft

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johnseidts
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Wanted- WWII Carter WO Throttle Shaft

Post by johnseidts » Fri Nov 24, 2017 9:03 am

I need a new throttle shaft for a WWII carb. NOS would be best, but good used would be fine. Thanks.
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Re: Wanted- WWII Carter WO Throttle Shaft

Post by Chuck Lutz » Fri Nov 24, 2017 9:26 am

John....

The flange and the throttle shaft do wear out and allow air to get in and that is why the flange may need to be bushed. if you mic the shaft at both ends you can tell if it is within spec and reusable or not.

i had some NOS throttle shafts I sent to Scoutpilot to rebuild/restore some 539s but ran out. The plain shaft without the three-armed bracket on it show up on ebay but fitting/peening them to the three-armed bracket is not a simple/easy task according to some on the gee.

Before you purchase "good used" be sure that it is within spec!
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Bantam T3-C 1947

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Re: Wanted- WWII Carter WO Throttle Shaft

Post by Scoutpilot » Fri Nov 24, 2017 11:09 am

If you mic the shaft and the flange bores keep in mind that any gap greater than .005” is probable vacuum leak. The shaft and bores wear into an egg shape so you need to measure the shaft where it passes through the bores in at least three locations around the shaft. The shaft cannot be less than .310” OD, nominal. The bores cannot be greater than .313” ID, nominal.
'70-'71 'A' Batt., 377th FA, 101AB
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LOW LEVEL HELL.
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Wanted- WWII Carter WO Throttle Shaft

Post by wo2jeeper » Fri Nov 24, 2017 2:16 pm

Have the shaft when needed and bushings to.

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Re: Wanted- WWII Carter WO Throttle Shaft

Post by johnseidts » Fri Nov 24, 2017 5:20 pm

Hi,
We pulled the carb due to a vacuum leak and I have the specs from the book (.3125 is factory). The machinist says it is too worn to repair, and too worn for him is too worn for me. Wo2 keeper, please PM me to let me know what I need to do to get one from you. Thanks!
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Re: Wanted- WWII Carter WO Throttle Shaft

Post by Chuck Lutz » Fri Nov 24, 2017 5:38 pm

Or...send your flange assembly to Scoutpilot to give you an estimate if you don't want to do the job yourself. Be VERY careful as the Carter factory did not always drill the throttle shaft holes in the flange in the center of the place where it goes and if it is offset, then installing drilling/bushings may break the flange casting.

I would suggest you get an opinion on your throttle shaft from someone who has rebuilt hundreds of these carbs, not from a machinist. No offense towards the machinist .....

By the way, what were the three distinct measurements around each end of the throttle shaft where it rides in the flange anyway? Just curious....
Chuck Lutz

GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
Bantam T3-C 1947

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Re: Wanted- WWII Carter WO Throttle Shaft

Post by johnseidts » Sat Nov 25, 2017 6:47 am

Scoutpilot,
Thanks for your advice. We had the specs from the Carter manual. We found the first vacuum leak on a loose fitting into the carb, which we thought would solve the problem. When we still couldn't dial in the idle, we disconnected the carb linkage and I rattled the throttle shaft with visible deflection- BINGO! My guy does excellent work that I would be willing to have go on my airplane, if that is any qualification. Good to know you are an alternate.
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Re: Wanted- WWII Carter WO Throttle Shaft

Post by Scoutpilot » Sat Nov 25, 2017 7:05 am

If you are going to have him do the job and he’s never done this particular flange, please advise him that when he reams the bores for the bushings to NOT REAM ALL THE WAY THROUGH as this will create a pair of gaps deep enough to disturb the fuel air mixture ratio and you will not be able to control the idle. Ream only to the depth that matches the bushing length.
'70-'71 'A' Batt., 377th FA, 101AB
(Slicks and LOH's)(Col's LOH Pilot)
'71-72 CHARLIE TROOP,
16TH AIR CAV, 1ST AVN BDE (AEROSCOUTS)
LOW LEVEL HELL.
'46 CJ2A
'47 CJ2A
'48 CJ2A
'48 B1PW126
'69 CJ5

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Re: Wanted- WWII Carter WO Throttle Shaft

Post by johnseidts » Sat Nov 25, 2017 7:13 am

Scoutpilot,
So if the bushing depth is shorter than the wall thickness of the throttle body where the shaft runs through, and you bore all the way out to the outer diameter of the bushing, it will leave a small void on each side which will disturb the mixture? What if the bushing spans the thickness of the throttle body wall? Doesn't that eliminate the issue?
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Re: Wanted- WWII Carter WO Throttle Shaft

Post by Scoutpilot » Sat Nov 25, 2017 7:42 am

Think in a linear fashion. The bushings I use are .5” in length and .375” OD. Ream only to 1/2”. Reaming all the way through leaves a deep circular gap in the bore around the shaft because the bores are longer than .5” with the linkage side bore being shorter than the accelerator link side bore. This gap is what disturbs the mixture. The bushings themselves must be reamed to .3125, ID for a new shaft. Using a used shaft will only work for a relatively short period of time compared to a correct sized shaft. An oversize NOS shaft may not be able to make up for the egg shape wear in those bores and leave you with a smaller vacuum leak.
'70-'71 'A' Batt., 377th FA, 101AB
(Slicks and LOH's)(Col's LOH Pilot)
'71-72 CHARLIE TROOP,
16TH AIR CAV, 1ST AVN BDE (AEROSCOUTS)
LOW LEVEL HELL.
'46 CJ2A
'47 CJ2A
'48 CJ2A
'48 B1PW126
'69 CJ5

johnseidts
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Re: Wanted- WWII Carter WO Throttle Shaft

Post by johnseidts » Sat Nov 25, 2017 6:25 pm

I get it- the butterfly can't seal against the sides where the shaft protrudes into the inner bore of the throttle body, so you always get extra air and a leaner mixture which is hard to set appropriately. Thank you for the explanation.
John K. Seidts RN:
Wanted to Buy any aircraft parts or aviation items
Wanted- WWII US Medical and Engineer Items


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