140 or 150 is not the way to go..................simply reline 64.5mm piston for a 180 kit, 25% power increase, just tune carb to suit, kits bigger than this are lumpy and oilways have to be redirected, (more expense) kits available of the shelf exchange for
The seeley framed 250cc bike lejeune (& hattori (?)) rode in the 1980 SSDT was the RS250T, it used another type of cylinder (external oil pipe to be used because the big bush cut through the internal oil channel).
I believe those engines have never been for sale.
I think this is an individual/shop conversion rather than a Honda works bike: why would they use the cylinder of their new tlr in a +/-4 year older (design) bike?
Honda Rtl 250Sf 1985 Manual And Parts List
in Honda
Posted
'89 partslist:
http://honda-trials.com/_sgg/m8_1.htm