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TR4/4A TR4A Carb enemy is time vs miles

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J

JDstr4a

Jedi Hopeful
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Finally got around to going through the carbs, before I put on any miles other than around the neighborhood,and it's probably a good thing. 13 years in the barn were not kind to them, even with less than 20k miles. I have a question about the "notch" in the bushing screw (1st picture.) I can't figure it makes any difference but thought I should ask.
DSCN0649.jpg

Before shot, everything is cleaning up well and all rubber seems ok.
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Chunks that fell out during disassemble!
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fine powder from the float chamber corner!
DSCN0654.jpg

hopefully I'll get the other done today too.
Thanks
JD
 
Hard to tell from the picture but the locating tab on the outer perimeter of the air valve diaphram, looks like it got "squished".
If you intend to reuse the diaphram at least make sure the tab goes back in it's proper home.
 
Thanks, probably spun the diaphragm when I pulled it apart, the tab looks pretty good. Here are some better shots of the groove. Maybe the nut part was in a vise and someone used a screwdriver/hammer to get it apart?? the o-ring seems in pretty good shape.
DSCN0663.jpg
DSCN0662.jpg
DSCN0661.jpg
 
Looks like corrosion to me. Irregular outline and pitted surface suggest it wasn't done with a screwdriver or something like that. Likely that flaky stuff started as some sort of metal that laid up against the screw, probably combined with some water that got in there, and caused a dissimilar metal (electrolytic) corrosion cell. Note that when assembled, the notch would be exactly at the bottom of the float chamber. And there is a discolored area leading from the corner up to where I'll bet the notch was oriented.

From what I can see, though, it shouldn't affect anything. The groove for the O-ring seal appears to be intact. And the screw just positions the jet (for the mixture adjustment).

Diaphragm looks usable to me, but it's best to stretch it gently in your fingers and look for any cracks or incipient pin holes. I also agree with Poolboy, it looks like it was improperly assembled before with the tab not in the notch. Just be sure it goes back into the notch (which may mean you need to take the diaphragm loose from the piston and put that tab in that notch). The important bit is that the piston has to be held in the right orientation or your mixture will be off.
 
I believe I'd go ahead and change that O-ring. I have it listed as a #114 if you look around locally, like at a NAPA.
 
Also, at a minimum, check the bore on the bottom bowl as that is the sealing surface for that o-ring. You likely will need the o-ring for the jet adjusting screw, on my carbs that is typically where I see it leaking.
 
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