Cooper is a brand of vintage off-road motorcycles that were manufactured in Mexico throughout the 1970s and into the 1980s. When production first began in 1971, Cooper motorcycles had Italian-made engines, but they would eventually change to Sachs engines.
The engines were mounted onto either an enduro or motocross frame that was manufactured by Islo Manufacturing in Mexico. The bikes were then exported to the United States where Frank Cooper distributed them, hence the name Cooper.
Bill Grapevine, an American trials enthusiast in the 1060s, designed a trials bike, the GRM (short for Grapevine Racing Machine), and Cooper/Islo were contracted out to produce over 1,500 of them. These bikes are very rare today, and parts are hard to come by.
Cooper dirt bikes were fairly popular through the 1970s since they were affordable, but they couldn’t handle the competition. Cooper Motorcycles and Islo Manufacturing were purchased by Honda in 1982, and their names would no longer be used.
14 Comments
Murray I checked the manual I have for my 74 mx250 5 speed and the head bolt torque is 40 ft lbs. I don’t see why it would be different on yours
Who manufactured the lower end on a Cooper 73?
Can any one tell me a cross reference for the brake shoes for the rear wheel for 1973 Cooper 250MX? Any suggestions for rear drive cush? Also looking for ignition parts. would appreciate any help or suggestions.
Thank you
I am restoring a 1971 Cooper MX and am just putting the engine back together. Does anyone know the head torque settings in ft. lbs. for the ISLO 250 cc.?
When you used the Suzuki piston did you have to cut the front and back skirts of the piston? The reason I ask is the repair manual says to use a Yamaha piston but you have too cut the skirts so piston will not hit the crank.
No, the Yamaha is for mx. The Suzuki you need to make a 1/4 inch spacer for the bottom of the barrel. The spacer gave the bike a lot more low end.
We had a Cooper dealership from 73-78. We raced Enduros, Hare Scrambles and Trials. Dad started with an old four speed and then upgraded when the five speed came out. I ran trials on my 74 GRM. A most impressive upgrade for performance is to remove the original piston, place a .093″ aluminum spacer under the cylinder and use a 250 Suzuki piston. This dramatically increases the lower end by changing the port timing. They will compete with the competition with this modification.
G’day fella’s the porting was different for enduro and mx coopers. In Australia Blair Harley imported them from the factory. I happen to have the original blueprints for the engine, pistons and a few other pieces. I’m trying to get hold of a few kickstarters at the moment which are proving to be a bit difficult. I have one MXer and 3 enduros. All in need of a restore.
Hi Rob
Do you still have your Coopers, I have a 73-74 Enduro but the engine and frame must be for the MX . If you are interested in selling one of the Enduros lets know.
Warwick
Hi looking for bits for my cooper rear wheel also my no 0410383202.cheers don.
Hi Don! You should call or email http://www.dubyausa.com. They offer full wheel restorations.
I have purchased a BSA Alloy Clipper for restoration. It has yellow enameled handlebars with unusual bracing. Obviously made for a dirt bike. Were these handlebars originally made for a Cooper?
Thanks, Kenny
@WT Schuberg – Which model have you got? Is it the four speed bike or the 5 speed bike. As I recall, the 4 speed all used the same up pipe. The 5 speed used both up and down pipes. I do not know if they used the same gearing or porting, for either mx or enduro. I owned a ’73 4 speed that I bought new in ’73, it was the enduro model, with a steel tank. There were some engine changes made to change the porting, and make it have more torque.
I have two Coopers; one MX, one Enduro 250. I’m looking for an exhaust system for the Enduro, not sure if the one pipe fits both.