Vintage Dirt Bike Q & A

Hello and thanks in advance,

I'm purchasing a 76 MT-250 in fair shape, I'd like to eventually build it up as everything seems a liitle "tired" right now.

From what I can gather thew MT motor was unchanged during 74-76.

Beside the oil injector is their a big difference between CR and MT motors?

Will a CR top end bolt up to a MT lower end, CR piston good in a MT cyl ?

What yr CR engines share parts with the MT ?

Thanks again,
JimS

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bikes of various sizes, shapes, colors, ages, and purposes

I may not have this right but I figure someone will double check me. I've only had my MT about a year so I am still learning myself.

The MT may have stayed the same but the CR and MR changed. The best year for swap compatability would probably be from a 1973 CR250. Problem is the MT had bolts that went all the way through the cylinder/head while the MR/CR cylinder bolts to the cases and head bolts to a different pattern of bolts on top of the cylinder. BTW: Don't lose your MT head nuts, dealership want ~$20 a piece for them.

The carburetor manifold bolt pattern is different too, so if you do find a 1973 CR250 [head, cylinder, piston] you also have to pick up intake manifold and carburetor. Two bolts vs. four.

I have a ~later MR cylinder and the porting looks to be quite different. You couldn't just make an adapter plate to bolt it up.

The transmissions are interchangable but the MT is a wide ratio and the CR a close ratio. I think the MT trans into a CR for people that do anything other then MX is a more common swap since it makes the CR better suited for other things like slow trails and desert races.

Mine just has an after market pipe, a fresh top end and some really nice Metzeler MX tires. Most of the street gear was stripped off before I got and it still has a lot of heavy items like steel rims. I have gotten very positive comments from a former racer who rode it when I first bought it and after I worked on it. I guess I did a good job because he said it felt like a CR and was pretty enthusiastic about the power. He thinks I know how to tune!<haha>

I mention this because you may have a tough time finding the CR top end. The swap has been known about for years and even if MTs weren't eating up CR cylinders, the CR MX riders surely wore out their fair share. A well tuned MT in and of itself is a lot of fun.

That is after 1973.

Thanks for the info ricortes,

Where did you find an aftermarket pipe for it ?

I need to go over the chassis first and replace the wheel baerings along with swingarm / steering head bearings and work on both brakes before I go at the motor.

One thing I haven't spotted for it is side panels, any known sources or is it a hunt and peck method?

Thanks again,
JimS

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bikes of various sizes, shapes, colors, ages, and purposes

Got almost everything from eBay. It was a lot of parts, only thing I could salvage from the first engine was the clutch basket, mag/flywheel, stator, kick starter, carb, and clutch cover. I think it took 3 engines to make one good one. Still have a few spare parts I think. The good news is nothing was over $100 included the original purchase of the MT.