I picked up this used BMC frameset in a trade. there appears to be some dirt/dust/whatever inside the frame tubes. i'd like to clean it out.

the tubes are carbon joined by BMC's wackadoo aluminum lugs.
could i just run water through it with some dish soap, then leave the frame outside to dry? my concern is that i end up screwing up the resin inside the frame, so i hesitate to use any real chemical cleaner.

I am no guru but I would leave the inside alone, unless there is a bunch of loose debris that you can get out just by inverting the frame.

+1. Shake out whatever you can. Any dust might be CF dust and is better off inside.

Compressed air? Lp

alright. I'm just a little obsessive about trying to make things like-new-or-better, i'll chill with the cleaning

"screwing up the resin"??? "CF dust"???

Spray it down w/ Simple Green, rinse w/ the garden hose, leave it outside to dry (or, if you're somewhere where the weather sucks...which means pretty much anywhere in the USA...in a warm room), badda-boom, badda-bing. Don't overthink this crap.

He's right, don't overthink this crap. Whatever dust is inside your frame doesn't matter. Leave it alone.

Bandwagon jumped. I agree, no touch. Unless it's rattling or blocking the drain hole just leave it. GL

Put it in the washing machine the next time you clean your helmet.

You're going to use water and dish soap and are concerned with screwing up the resin? This is dish soap we're talking about. The same stuff you put your bare hands in. And probably ingest a little bit of it too if you don't rinse fully.

The bike isn't made of cardboard and elmer's glue. Water and dish soap won't screw up anything.

Roto-rooter?

Right, that's why I default to dish soap. Gets rid of grease and dirt AND you can drink it. A cyclist's best friend.