I've been at this building lark [ bikes and cars] for over 50 years - 40 + of those years in a professional design / manufacturing capacity [ replica sports cars ].
I certainly don't know it all, and frequently have to ask others for advice / help, but I don't consider myself "dumb".
I can whip up a true spaceframe chassis design in a morning - but wouldn't even attempt to tack it together given my lack of welding skills.
To me a "Dumb" question is one in a situation
that you've never come accross before - but to others may be matter of fact -
to you it's a valid question - to them it's "dumb"."Explain the theory of relativity young Beachcomber" - a question from my science tutor 50 odd years ago ..........."How the fuck do I know", was the instantaneous response.
Ask the same question to some guy called Einstein and no doubt he'd have said "what a dumb question".
It's all a matter of your knowledge / experience level against someone else.
When I was sixteen I managed to break a pushrod on my AJS 250 CSR. Simples, take the head off and replace offending item. There I sat outside my Dad's garage - but do you think that effin head would come off ?
It appeared to be "stuck" - unlikely as the bike was only 3-4 years old, but I'd encountered a similar problem once before with an old Velo Racer where the steel studs had corroded against the alloy head. Several broken screwdrivers and a broken alloy fin later, I eventually I stopped a guy who lived around the corner and who rode a Black Shadow to ask for help / advice.
Within 2 minutes he discovered the internal nut that held the last fixing bewixt head and barrel. I suppose he could have thought I'd asked a dumb question - given the OBVIOUS answer, but he just spent the next 2 hours overseeing as I carried out the repair.
Now, when I'm stripping something down for the first time [ without the benefit of a manual ] I look for hidden / non-obvious fixings !
I'm also NOT embarrassed to ask questions, that may well appear dumb to those who know. Yes of course you can have a go yourself, and you may stumble accross the correct answer - then again , you might not ...............
The other day I asked the guy that does our plating - "Can we Gold passivate aluminium " - a dumb question ?
He obviously knew because it's day to day business, but I'd never encountered the situation before. I now know the answer and will not have to ask such a "dumb" question again.
My point [ and probably the concencus ] is that the first time you ask
the question, to all around it might appear dumb ............personally, I don't have to ask it again.
Is it maybe just the "level" of dumbness that offends 
?? 
