XT500 TT500 Forum www.xt500.co
https://www.facebook.com/groups/xt500fo ... 7243103845]XT500 TT500 Forum www.xt500.co
Beitrage eines Todd Booth:
1973 Yamaha concept engine 043-0-001 built as first off-road four stroke pre-prototype for testing. Fully sand-cast with transmission and decompression components from SC500 and OHV technology likely derived from XS1. Chassis was largely common to MX360. In conversation with Yamaha’s USA 1973 test supervisor, here are his recollections:
-Wanted 500cc four stroke for US sales
-TT500 specs determined after testing this engine
-Comparison motorcycle was Ariel Red Hunter
-Engine was never disassembled in USA
-This engine made less than 20hp
Notable differences with TT500 are:
-Wet sump design (TT500 is dry sump)
-No points ignition (TT500 has points)
-Oil pump at points location
-Spark plug and cam chain on opposite sides
"Serial 043-0-001. Deciphered…project 043, “0” concept, “001” first built"
"43mm intake and 37mm exhaust valves. Small hole at 2 o’clock is bleed hole for the kickstart activated automatic decompression system. Cylinder pressure is bled directly from a 2mm hole in the bore the hole in the cylinder head to bleed out the exhaust port to the exhaust pipe"
"SC500 decompression assembly in the foreground. 85.5mm bore x 83.25mm stroke for 478cc displacement. Displacement was limited by crankshaft clearance to transmission gears"
"Various modifications for oil control. Elaborate internal passages for crankcase venting"
"Oil scraper and oil migration hole"
