Once I knew the Y manifold was ordered, I removed the old one. Out of curiosity (of course) I looked at the carb slides, turned the twistgrip a bit, and watched the nearside slide lift up. i had worked out that the offside slide had a diaphagm (obvious from looking on top), so I poked my finger in and lifted the slide. And it stayed up when I released it. Hmm. Not good.
Today I dismantled it carefully. The diaphagm feels stiff but is otherwise undamaged.
Are replacements available, and if so, at what cost?
I continued dismantling various parts such a float chamber etc. The float valve seemed OK so I left it alone, but gave the float bowl a good clean out.
I saw what appeared to be an adjustable needle located underneath the nearside body, and "eyed things up" to see where it was in respect of the main choke -- On the engine side, and looking in, not much to see, but my probing finger felt something sharp poking up.
I carefully screwed in in to record its position, (1-1/8 turn), then removed it completely. A screw with a reduced parallel end, but no tapered needle as I might have expected.
Probing with my finger again, the sharp projection is still there. It looks as if the needle end has dropped off, probably overtightened by a previous owner, the one who ruined the thread in the front forks no doubt.
So, where can I get a replacement?
Further searching on the www found these two sites:--
www.offmoto.com/viewtopic.php?id=6686
ttr250.com/Carb/TTR250_carburettor_strip_and_rebuild_guide.htm
The first link suggests the needle adjuster is item 42. In the second link, a 30mm Teikei for a Yamaha is dismantled and rebuilt, so maybe a Yamaha dealer.
I have NEVER ordered a Yamaha part from a Yamaha dealer. something I may need to learn.
Unless somebody here has a spare needle and decent diaphagm to part with.
Cheers, Les.