Hello, I'm Tyler From D37 California. I'm 18 and I have an insatiable need for flat out speed, as I am an expert level desert racer. I just recently took out my trusty and super agile 2003 CR125 for a day in the desert and to my surprise the engine seized. I want to rebuild it better with more power so my options are only to do so with a big bore kit but I am uncertain if even a bored and stroked 125 will produce the power I am looking for. So instead I got the crazy idea of putting a similar year CR250 motor (or other brand if needed) into the already well-dialed and excellent handling chassis of my 125. Do you think this could be possible? I know that the removing of existing mounts will be needed and custom ones welded in their place but that is not a problem, I am only concerned with the available space. Great Mag..... Dont Give Up On the Two-Stroke!
Tyler, I have some bad news, more bad news and some good news. First, the worst news is that putting a 250 engine in your 125 will ruin the super agile feeling and the suspension action. The feeling of a 125 has more to do with the torque loads and the gyro effect of rotating mass in the engine than it does with the weight. We just tested a Husky WR125 that weighs more than most 250 two-strokes, but it felt as light as a (surprise) 125. The second bad news is that you would have to cut most of the front frame cradle away and fabricate a new one, or weld one from a 250 frame in. That would poorly affect the heat treating of your existing frame. It would be cheaper and easier to buy a 250 frame, but by the time you buy the 250 frame and engine it would be far easier and cheaper to buy a whole 250 for those days when you want more power. In fact, for the price of doing a big-bore/stroke kit on your engine you could buy a decent 250 two-stroke. In fact, that is what I would do. Do a good clean rebuild on your 125. Make sure you determine the cause of the seizure. A bike like yours -- one that is doing the same thing you usually do - should not suddenly seize. It might be time for a new crank and crank seals, and make sure the engine is sealed up nice and tight while you have the engine apart. Then start shopping for a good 250. Any of the Hondas from 2000 on up make good desert mounts, and since the 2002 and later 250s aren't really great moto weapons, they are pretty cheap. -Karel Kramer