I have a 300ex. By this time next year, i wanna play around on some cross country and hairscramble races. Bone stock, its not really all that fun. Iv rode motorcycles all my life, and used to the wheel speed of a 2 stroke, so the slow 300 motor does not impress me that much. It doesnt have enough, it hooks up too much. But i intend to fix that, widden it, piggy backs, yada yada ya...... I was looking around for some +2 or +3 a-arms, and around here, they are hard to find. I was looking on ebay the other night, and found some a-arms off of a 400ex and the guy said that they would also fit a 300ex. This shocked me because i thought the 400 frame was bigger in every aspect, including a-arms. I was wandering if this is true, and what else will bolt up to a 300ex from a 400ex. because 400ex parts are alot easier to find. Or maybe i just like to find bargains on ebay........

 

The 400ex arms are a great upgrade for the 300. You gain about 4" of width. You can use a 400ex carb, on the 300, too. Other than tires and wheels that about it, for direct bolt-on stuff.

 

The brake calipers. front and back are identicle.

 

Can you drop a 400ex engine into a 300ex? Can you still use the 300ex transmission (so you can use reverse)?

 

The complete engine won't swap easily. The swingarm mounts through the engine on the 400. It goes only to the frame of the 300.

The cylinder is 12 or so mm bigger, so keeping the 300ex tranny, would be hard.