Circa 1973 GRM Islo Trialsmaster motorcycle photos & specs

GRM ISLO Trialsmaster – designed by Bill Grapevine and manufactured by Moto Islo S.A. of Satillo, Mexico. (GRM stands for Grapevine Racing Motors). The Only 250cc class trials bike that uses a frame made of aircraft quality 4130 steel tubing imported into Mexico from the U.S.A.

1973-circa GRM Islo Trialsmaster Dealer Sheet available at

1973 Dunstall 850 Norton Road Test / Specs – a different approach for Britain’s biggest Twin

Road Tests: Dunstall 850 Norton -a different approach for Britain’s biggest Twin, Rokon RT340 Automatic TCR, GRM Islo Trialsmaster (Grapevine Racing Motors designed by Bill Grapevine), Jawa 500DT, The Can-Am Brigade – four dirt machines with an innovative application of the rotary valve; Special Feature: Speedway! Zany, colorful racing tight as a banjo string; Competition: Superbowl of Motocross; Race of the Americas, Lima, Peru; Loudon Road Race National; Hang Ten U.S. Grand Prix; Technical: wire your Yamaha for night racing; Feature: History of Zundapp; more

500-DT RT-340

1973 October Cycle World Motorcycle Magazine Back-Issue available at