2003 Ec 200 into 2006 Ec 125 frame
 

Hi, was wondering if anybody could give me a little info. I have come accross a good cond Ec 200 motor 2003 model, and wanted to know firstly if the 200 range has changed significantly over the years in turms of motor spec. It seems that the motor has stayed neerly identical over the years ? and secondly if the motor would bolt right up into my existing bike. I currently love my bike and would not want to change, but we do a lot of very technical mountain rock riding and the 125 takes a little strain and I could do with some more bottom end. Any info would be greatly appreciated. regards Gary

The 200 shares its frame with the 250/300 bikes. The 125 had its own frame. Therefore, putting a 200 engine into the 125 frame won't be a drop-in replacement. I'm sure that it can be done with custom engine mounts. I've seen pictures of a KTM 200 engine put into a YZ125 frame with custom mounts. So anything is possible if you fabricate the mounting points.

Other issues that you will run into may be the carb, airboot, reed valve, and manifold. I believe the 125 uses different parts than the 200/250/300. You would have to look at the parts diagram to confirm.

IMHO, investment/time required to get it done properly just isn't worth it. You would be better off increasing the 125 engine to a 144cc.

You'd be money WAAAAAYYY ahead by just sending your carb and head to Ron at RB-Designs. You may not even need a 144 kit if you do those mods. The Gas Gas is fairly "loose" on it's squish band set up, and he cures that, which gives more power, better fuel economy, and easier jetting. That mod is only $75. Frankly, I don't think he's charging enough for it for what it does.
That would be my first step to test the waters. Then send him your carb. For $165 he puts a wing in the exit, cuts the slide, mods something in the passages to make your air screw actually do something tangible and rejets it. That's a lot less work than shoving a 200 engine in your frame, and you'd probably like it better anyway, 'cause that 200 needs the same stuff.

Check out his site: www.rb-designs.com