Originally Posted by visovm
As far as I can tell it does not look like the needle was ever shimmed with washers and the spring does not appear to be trimmed. Judging from the responses I should leave it this way.
Likewise, the best way to improve performance and throttle response would be to get a jet kit or spring for the TM33 carb, instead of fiddling with shims, and trimming of the spring.
I think it seems pretty clear the carb you have is stock and unaltered, so now the question really is "what problem are you trying to solve"? If things are running well now then why change anything?
The discussion about the spring and needle was interesting, but instead of shimming the needle why not just order a stock one with the adjustable clip and not worry about that aspect? I'd assume that the adjustable clip will eliminate any concern over spring preload.....
Or use your already modded airbox and add the kit from Jesse @ Kientech (I have been happy with that mod, though it lowers fuel economy).
I assume that was a typo about getting a jet kit for the TM33 since you have a BST?