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Worn carb throttle shafts


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#1 NYMalloys OFFLINE  

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Posted April 24, 2010 - 09:18 PM

Does anyone have any tips for repairing worn throttle shafts? In my case they are on a few old Walbro carburetors. The brass shafts are worn down, though the carb bodies all seem to be to within tolerance. Depending on the application, the throttle sticks (particularly on a shredder- no throttle cable control) or they run lean so I have to keep them partially choked even when warm. Replacement parts are no longer available for these and I don't want to buy any used carbs without knowing whether they have the same wear.
Rebuild kits that I used on an old Farmall tractor came with felt washers which went over the shaft ends, I'm not sure if this was to decrease air intake around the shaft or just take up end play. If anybody thinks this would help on these walbro carbs, or if you have any other suggestions, let me know. Thanks.
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#2 DH1 ONLINE  

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Posted April 24, 2010 - 09:31 PM

Check out "1972 MF12g" thread in Massey Snapper section, shows what I did to fix one.
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#3 olcowhand ONLINE  

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Posted April 25, 2010 - 08:28 AM

If the shaft is the worn part, it's not easily fixed and best to replace the shaft. About the only way to repair the shaft is to build it up and more than likely you would ruin the shaft trying. About the only way to do it would be cut a nylon/plastic sleeve the width of the groove, hold it in place while sliding shaft into hole. I would be afraid of binding if it moved out of place. With a good body, I'd just buy a new shaft. If body has wear too, replace shaft & bush the body.
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#4 NYMalloys OFFLINE  

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Posted April 25, 2010 - 12:54 PM

I read over the the "1972 MF12g" post suggested by DH1, and I'm not sure how the copper tube would fit. The throttle shafts I have are only worn on the upper section beneath the throttle cable plate and the beveled section where the throttle butterfly mounts. It seems that either machining a new part or "building up" the old would work but I don't have the needed tools. As for purchasing, I've tried to find parts for these walbro carbs for a while but other than rebuild kits (needles, seat gaskets, floats, bowls, etc) I can't find anything. My local parts guy tells me that Walbro discontinued parts for the old LME carbs which were used on a lot of the early Tecumseh H and HH engines. If anyone knows an NOS parts source, I would appreciate the information. Thanks.

#5 DH1 ONLINE  

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Posted April 25, 2010 - 02:24 PM

I read over the the "1972 MF12g" post suggested by DH1, and I'm not sure how the copper tube would fit. The throttle shafts I have are only worn on the upper section beneath the throttle cable plate and the beveled section where the throttle butterfly mounts. It seems that either machining a new part or "building up" the old would work but I don't have the needed tools. As for purchasing, I've tried to find parts for these walbro carbs for a while but other than rebuild kits (needles, seat gaskets, floats, bowls, etc) I can't find anything. My local parts guy tells me that Walbro discontinued parts for the old LME carbs which were used on a lot of the early Tecumseh H and HH engines. If anyone knows an NOS parts source, I would appreciate the information. Thanks.


I just used a cordless drill and a set of drill bits to drill the top of the carb (did not touch the bottom) until I got a tight fit with the copper tube in the top of the carb, and then used a small round file (chainsaw file) to make the inside of the tube big enough to slide over the throttle shaft. It might not be perfect but alot better than before and the motor has a smooth steady low idle.
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#6 29 Chev ONLINE  

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Posted March 04, 2018 - 04:07 PM

If the shafts are brass they will tend to distort easily with heat.  If you can take the shafts out and gently clamp them in a vise you may be able to build the worn areas up with solder using a propane torch or larger soldering iron.  Get the brass nice and clean - scotchbite pad or fine sandpaper and then scrub well with a small wire bush and soapy water.  If using a propane torch keep the heat low so you can get the solder to stay put where you have applied it while you solder any other worn areas - a wet rag wrapped around the areas you have done may help.  The solder should be easy to file by hand to shape the areas back so they are round and the correct diameter. 

 

You could also try some JB weld rather than solder to build up the worn spots and file to shape once cured.

 

Just suggestions that may help. 


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