Is that possible?

Also, what size (cc) is the 303 engine, does it have a reed valve and how would its power characteristics vary from a standard 240 engine? Any ideas?

Only asking as a good 303 engine has come up and I am thinking will it swap over with my tired 240 engine while I get that rebuilt/refreshed?

Many thanks.

If memory works ... 249cc , reedvalve . It should basically bolt in place , but will need exhaust and airbox /carb mods to work correctly.

Glenn

303 engine will bolt in, might have problem with the large 303 flywheel case, touching the frame, where the c shaped tube flywheel protector is. The exhaust will fit straight on, although the outside diameter of the 303 exhaust port is 38mm, compared to 35mm for 240's and 300's. You would have to fit the inlet manifold from the 240 maybe or a 300, as the carb position is different. 303 engine (249cc) last of the piston controlled ports, probably the best motor, should have 'high exhaust port (which allowed it to rev) and some had a squish cylinder head, just like a 240. The clutch is bigger on the 249cc engines(and 241 onwards 212cc engines), the extra power, needs to be respected (to control wheelspin)but the larger clutch allows plenty of clutch control.

Edited May 14, 201313 yr by ask greeves

It will fit but I had to modify my frame rail for the flywheel cover, exhaust port is larger on the 303(250cc) than the 240(212cc). I had the 303 exhaust cut and welded onto my 240 pipe. Its not a reed valve motor they came with the 5 series engines and I also bought a genuine 300 carb inlet manifold and hose for the 303 carb which is a larger carb than the 240 had. Worth the effort though in my opinion its much better with the bigger motor in.

Overhere in Holland we have some one who build a 305 engine in a 240 frame.

Frome what i have heard it was no problem, but he used a aftermarket exhaust, i believe it was a WES system.