I took apart the carbs, and after reassembly, the throttle linkage now looks like this (that specific part was hell to get together, with the various springs etc.). I don't like that there's a "gap" in there (to the left, by that white plastic piece), but I re-did it like three times, and couldn't get it any better than this. And I can't find any pictures of how it's supposed to look.
There's now some light friction when releasing the throttle, and also some slight "slack" in the mechanism, so that the right throttle plate (front cylinder) doesn't always return completely to baseline position when the left plate does (though by a light finger tap on the arms, it does go back fully). We're talking tiny differences – but I assume it makes all the difference. Any thoughts?
@andreas welp... lil oopsie there.... you should never take the carbs apart. =/ and you are unfortunately experiencing why. There should be NO drag at all on the linkage. If there is, then youll need to re-do the assembly, use grease on all moving surfaces and make sure it goes back together correctly.
also make sure you lubricate your throttle cable and that it isnt pinched or curved at a sharp angle. additionally make sure the surface between your throtle sleeve and handle bar isnt full of shmoo.
@TJ Yeah, I certainly learned this the hard way . . . To be honest, I unscrewed the carbs only to make it easier to get them out -- was blissfully unaware that I would F up a critical mechanism by doing so. Ah well. As for that little "gap" seen in the picture, is that normal? I would've expected it all to press together nicely, but that's all governed by the length of the two metal pieces that the joining screws go through (one is seen in the upper part of the picture) -- it's not possible to make the distance between the carbs any shorter without grinding those shorter. So, is it supposed to look like this? I really tried to find a photo to compare with, to no avail. What's even the purpose of that white plastic ring thing? I'd imagine it to be like a "seal", but it doesn't seem to fill that purpose very well now.
Anyways, so grease is the way to go then, good. I will do that. As for the cable, it seems dandy at least (the issue was present already when I had the carbs on the table).
My last question is: now that the carbs are on the bike, it seems to run alright, but the front cylinder (the one fed by the "linked" carb) exhibits some light exhaust bangs (or "puffs" rather) at idle. Is it likely that this is due to the above linkage issue, i.e. that the throttle plates are now slightly mismatched at idle? Or would this be a separate issue altogether? I tried to adjust the mixture screw on that side, to make it a little less lean, and this did alleviate the exhaust puffs, but made the bike run erratically and made the spark plug sooty on that cylinder (yes, I know now that there are in fact TWO spark plugs per cylinder, but I didn't know that before yesterday😅).
Thanks for your help man!
@andreas unfortunately at this point, theres no baseline. carbs have been separated, they are now out of sync, youve messed with adjustments, i cant really poiint ot what the issue could be because there are way more variables in play. you need to get the carbs assembled properly then synced. you can benchj sync by looking at the butterflies and making sure they are both just barely covering opne of the pilot holes in the venturi. then sync on the bike. youll need a syncronizing tool which can be found on amazon. then go from there. you may need ot buy a junk set of carbs to visually see how those carbs should be asembled. and a plastic ring is not a seal, its a bearing. It takes friction between surfacesand reduces it by being plastic and slippery.
once all this has been done, THEN you can start looking at tuning.
@TJ Thanks for the reply. I followed your advice – disassembled, cleaned and greased all the moving parts and put it back together. Issue solved. No friction, no "gap", and the motor seems to run well. There is, however, some very light exhaust pops from the front cylinder still, but they can't even be heard really, only felt by holding a hand behind the exhaust.
@andreas for further diagnostic for tuning - check this out - https://shoptjbc.com/community/brutalforums/topic/176621/tuning-your-carbureted-honda-shadow-everything-you-need-to-know
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