i would like to learn how to maintain and repair my clarinet and would like a "dummy" clarinet to practise on. i have a very good Haynes manual to follow but am not confident to do it on the real thing yet.
If you are handy this way, you can find yourself an instrument that needs a lot of repair at your local music store or online and try rebuilding it. You can find parts suppliers online using a search engine and probably even find articles describing techniques and processes. You can take your time as a beginner and allow your skills to develop naturally, and if the results are less than stellar, you can take it apart and try again. People that do this kind of work are usually very good about sharing their wisdom, so get to know some of them.
One of my clarinets came from a private advert, and I paid the princely sum of £15 for it. Didn't dare knock the price down more! There's absolutely nothing wrong with it, but for that price, I'd be happy to experiment on it as a budding clarinet doctor.
Look around - music schools, private ads, ebay, etc. Put a wanted ad in the local shop, newspaper, etc. Might as well work on a real one rather than a dummy...
Background: ~8 years working in a band instrument store and repair shop, mostly as a sales rep, but did some minor instrument repair, owned by a man known throughout the country for band instrument repair.
BEWARE!! (cue organ music)
To use a term I initially heard from the aforementioned store owner, there are instruments, and then there are ISOs: Instrument-Shaped Objects. There are a LOT of instruments coming from bad factories (it used to be that any musical instrument coming out of, say, China was no good; nowadays it's a matter of which factory they're coming out of, because there are a lot of good horns coming out of the east) that are not worth the materials it took to make them; instruments that are so cheaply made that the store wouldn't even repair them because after "30 feet or 30 seconds", they couldn't guarantee their work. Any number of things could be wrong with them, but especially the metal parts (of which clarinets have lots) were so soft that they did not resist bending as well as they should. As a result, if you're attempting to repair them, especially if you're not completely familiar with what you're doing, then it becomes difficult to the point of impossible to know whether the difficulties with which you're struggling are a result of ineptitude or faulty equipment.
If you're already familiar with musical instruments, only purchase instruments whose brands you recognize. If you're not sure, find a music (repair) store that you trust and ask them if they've ever heard of it, and what they think of it.
Incidentally, this counsel applies to people buying instruments to play for precisely the same reason.