). Ever wanted to see whether the passageway in a carburettor was actually clean ? Then what you need is a tool like an otoscope or ophthalmoscope as is used for checking the insides of eyeballs or ears ! He wasn't using his any more, so he gave it to me and it works great !
For the first time I can easily visually confirm the condition of the passageways and jets. These things are available pretty cheaply on eBay, but look for one that has several powers of magnification so you can more easily see down channels of different depths. 
