...pulled the linkert M74B due to leakage & to set the float (brass should be set at 5/16"to 3/8" right?) & I noticed upon inspection that my throttle shaft has a lot of movement up & down & that the plate has ground lines into the main body bore. Should I replace the shaft, replace the bushings, and/or hone the bore? Palmer mentions that too much play can create a lean condition & the shaft should have only .002 play. Am I reading this right???
Thanks in advance for any input.
Linkert M74-B throttle shaft
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Cotten
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Re: Linkert M74-B throttle shaft
Was it running lean? Just replace everything anyway.
The up and down play should be eliminated by the spiral spring on top, under the throttle lever.
Honing the bore requires an oversize throttle plate, and a carefull swaging of the venturi out to size. (The venturi is nearly always shrunk to smaller than the existing bore anyway.)
Brass floats don't.
But if you think you have no choice:
If it doesn't leak air in hot water, then weigh it. If it weigh 12g, try it at .400" (Nearly out of travel).
If it weighs 9g, you can try .375".
Expect reduced gas mileage, and accellerated wear upon the pivot pin and lever.
Meanwhile, while your carb is off, ritually pressuretest your manifold with dilute dishsoap. It could save you a lot of tail-chasing later.
The up and down play should be eliminated by the spiral spring on top, under the throttle lever.
Honing the bore requires an oversize throttle plate, and a carefull swaging of the venturi out to size. (The venturi is nearly always shrunk to smaller than the existing bore anyway.)
Brass floats don't.
But if you think you have no choice:
If it doesn't leak air in hot water, then weigh it. If it weigh 12g, try it at .400" (Nearly out of travel).
If it weighs 9g, you can try .375".
Expect reduced gas mileage, and accellerated wear upon the pivot pin and lever.
Meanwhile, while your carb is off, ritually pressuretest your manifold with dilute dishsoap. It could save you a lot of tail-chasing later.
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57FLH
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Re: Linkert M74-B throttle shaft
Thanks for the advice Cotten.
Yes, it has been running lean & therefore hard to start. I'll do a manifold leak test to check that, pitch the brass float & put in a foam one I guess. The spring you mention is hidden under the lever? I can't see it & haven't pulled it apart yet so i'll check that.
The honing will have to wait for a rainy day cause I don't have one & can't afford to get it or shaft/plate parts right now.
On the float, do you have a recomendation of which kind? I vaguely remember someone saying you had really good ones? True? Let me know. Thanks!
Yes, it has been running lean & therefore hard to start. I'll do a manifold leak test to check that, pitch the brass float & put in a foam one I guess. The spring you mention is hidden under the lever? I can't see it & haven't pulled it apart yet so i'll check that.
The honing will have to wait for a rainy day cause I don't have one & can't afford to get it or shaft/plate parts right now.
On the float, do you have a recomendation of which kind? I vaguely remember someone saying you had really good ones? True? Let me know. Thanks!
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Cotten
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Re: Linkert M74-B throttle shaft
You won't find a "foam" float in any catalog that resists all modern pump fuels.
The creamy colored ones last about 15 minutes in Midwestern P4gas. And it ain't even oxygenated!
(And they ain't "Armstrong"s either!)
The cork alternatives seem like a good bet, but their sealers are suspect to the foul gas, and cracking the seal while installing the pivot nut adds risk.
There is only one ultralight gas-proof float on the market for Linkert and Schebler carbs. I cut each one as a one-off service with my own stubby fingers and a '48 Logan lathe.
Hold our breath while you post me direct at liberty@npoint.net,... because they are NOT cheap.
But they are the best ever produced. Without exception.
...Cotten
The creamy colored ones last about 15 minutes in Midwestern P4gas. And it ain't even oxygenated!
(And they ain't "Armstrong"s either!)
The cork alternatives seem like a good bet, but their sealers are suspect to the foul gas, and cracking the seal while installing the pivot nut adds risk.
There is only one ultralight gas-proof float on the market for Linkert and Schebler carbs. I cut each one as a one-off service with my own stubby fingers and a '48 Logan lathe.
Hold our breath while you post me direct at liberty@npoint.net,... because they are NOT cheap.
But they are the best ever produced. Without exception.
...Cotten