So many questions!
Sorry if I miss any....
I basically seperate these engines into "groups":
Group 1 = AT1, CT1, AG100, AG175, late MX100 (with the leg-burner pipe). Single shifter shaft.
Group 2 = Most of the twin shock bikes not listed above, with 5-speed. Linked/2-piece shifter shaft.
Group 3 = The early 6-speed bikes (YZ125C/X, TY175, MX125C). Linked/2-piece shifter shaft.
Group 4 = Later 6-speed bikes. Single shifter shaft.
Group 5 = 85+ DT175.
Simple version is that :
all Group 2,3,4,5 engines will bolt into any frame that originally came with a Group 2,3,4 or 5 engine;
gearboxes (including shifter drums) are not directly interchangeable between groups;
top ends are interchangeable between Groups 1, 2 and 3 (but not between 4 and 5);
the engines got better as they got newer;
Group 1 engines have a larger diameter kick-starter shaft, all others are the same size and spline;
Gps 2 & 3 have a slightly shorter kick-starter shaft, compared to Groups 4 & 5.
the kick-start levers are shit and get worse as the get newer.
I've half-written a fairly detailed blurb on these engines - will finish it and post it up. It answers all of your questions plus most of the obvious follow-on questions.
No, a DT250 motor won't fit in your frame.
Yes, I have a
big pile of monoshock DT engine parts, particularly 175. Ring me on 04000 23847. I can deliver to CD5 if you can wait until the end of the month.
You shouldn't have a drama finding a pipe at your local wrecker if you have no luck here.
