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Discussion Starter #1
How much play is allowed before these need a bushing job?

I just got a carb with 26k original miles on it, thinking I would have one with no leaking shaft. There is a slight bit of looseness to the throttle, seems the same at the spring end as at the far end. I can actually see the tiny bit of movement while looking in the bottom of the carb. Too much, or is that normal before for the metal expands?

Thanks,
-Michael
 

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Discussion Starter #2
I know what you mean... I have an old E4ME that has a perfectly tight throttle shaft, yet the carb looks like it went through hell! This new carb looks like it has really low mileage, but the shaft has enough play that I think it'll need bushings after all (I can wiggle the shaft and hear a definite "click" as it hits from side to side).

Do the bronze bushings last a lot longer than the aluminum tb?
 

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I just rebuilt one from a 78 chevy van with very noticeable play. You could see how the bore was hogged out from the years of use. I put it back on to see how badly it would run and it runs just fine. It does have a bit of a vacuum leak there, but since its small and predictable its almost like an idle bleed.

If I spray carb cleaner at the shaft while its running I get a tiny rise in RPM, so as long as it passes smog I'm going to leave it. :)
 

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Cut the neck off any 30 cal brass - 3030, 308w,3006,300wm etc. Drill baseplate, install and lightly hone to suit throttle shaft. Obviously the primary shaft is more prone to wear and when installed make sure the throttle cable/linkage moves freely enough to allow a LIGHT return spring. Heavy springs and overtightening of the carb to the manifold are the greatest cause of wear.
 

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Another cause of accelerated wear is an improperly working/adjusted choke. Heavy repeated pumping @ startup will accelerate shaft bore wear.
 

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Discussion Starter #8
Thanks for all the replies, great help!

I think I will send this one out to get new bushings after the holidays. No point in getting the DIY kit for one carb... same price and someone more experienced can do it.

Doesn't seem much point in rebuilding a carb if I'm going to keep the same leaky shaft. That is the problem with my old carb--it's so worn I can't get the idle mixture right. This new carb has all the original factory settings (1980 model, has steel plugs in front of mixture screws), so hopefully new bushings will bring it back to as good as the day it was made.
 

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It seems to me that the rearward-oriented return springs would put all the wear on the back side of the bore, so it might help to hook them to the top side of the lever and run them forward. Another 90,000 miles and I'll know for sure.
 

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No, it won't heal anything, that's for sure. I meant as a preventative measure. I had just had the carb rebuilt when I changed the springs.
 

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Discussion Starter #12
Any difference between a bronze and brass bushings? It seems bronze is the common material, but found a place that does brass. Is there a big difference in wear?
 

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mhamilton said:
Any difference between a bronze and brass bushings? It seems bronze is the common material, but found a place that does brass. Is there a big difference in wear?
I would imagine that the bronze would be a little harder. I install B&S valve guides, they seem to work pretty well.

tom
 
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