Vintage Dirt Bike Q & A

I have an interchange question if you CR guys can help out I'd be really thankful...

The MT250 I have is a 1974 model...

What year CR/MR cylinders will bolt do this?

What about ignitions?

I have a line on a 76 MR250 cylinder and head and either a 73 or 74 CR250 cylinder and head (or is 73/74 the same?)

Will these bolt right onto the MR with no problems?

What years have the same bore and stroke and bolt pattern that will bolt right on?

I realize I'll have to get a bigger carb and diff exhaust, but I'm sure the porting is way better...

Thanks for any tips you guys might have on this.

Mike

The 73-74 CR250 top end will bolt on to the MT bottom end any year. The MR250 is interchangeable only with the 75-76 CR250. It will not work with either the 73-74 CR250 or any MT250. It does have useable parts like the kick start mech., the clutch cover, shift shaft, and the clutch will work on the MT250 bottom end. The MR250 cylinder and the 75-76 CR250 cylinders bolt to the cylinder at the bottom where the MT250 and 73-74 CR250 have long bolts holding both the head and cylinder down. Also the MR exhaust exits on the opposite side so the pipe will not bolt on. The igntion flywheels are the same from MT to MRs but the MR will not charge the battery it is meant to run the lights directly. If you run the 74 CR250 top end on the MT250 bottom end you need the CR intake and carb. The MT250 has two intake bolts the CR has four. Hope this is not tooo confusing!

Mike,

The MR will not work. Know this for a fact. Accidentally bid on an MR lower end on Ebay and for whatever reason was thinking MT. Got a really nice set of cases and tranny for an MR sitting here that is useless to me right now. My bad.

Not sure about the ignition though.

Loren

That stinks about the MR bottom end - did you put it out on the swap meet for sale? I know a guy that has an MR250 maybe he'd be interested. Gimme a price I'll tell him.
Mike

So can anyone tell me what year CR250 cylinders will fit onto the MT250 (1974 model) ?

Mike

The first response says a 73-74 CR250 head will fit any mt model year. my clymer manual showes the same thing just have to use the CR's carb and intake.

Turns out the cylinder/head/intake I can get is off of a 1975 CR250 - any chance that might fit onto the MT cases?

I realize I'll have to switch to a downpipe and that's okay - just curious if that 75 will mate up. I believe they use the same piston, have the same bore & stroke, just don't know about the mounting though my fingers are crossed - whadda you guys think 75 CR cylinder on a 74 MT bottom end?

Mike

Mike, the 75 used an up-pipe. It may? be the same pipe as a '76 but not sure.

Sorry but a 75 CR250 top will not bolt on to any MT250 bottom end. Only a 73-74 CR250 cylinder with the bolts that go all the way through the cylinder will work. In 75 they redesigned the top and bottom ends of the CR(same as the MR). They look similar but will not swap.

ok, so i swap a 73-74 cr250 head to mt 250 bottom along with the cr carb and intakes and how much payback do i get?

With a CR250 down pipe you have all the power of a 74 CR250. The only diff would be that the gear ratios are a little wider in the MT tranny but the motor would still cook.

so i locate and purchase a 74 cr250 carb that after purchase turns into a 75 cr250 carb - viola - so will the 75 carb with a 74 carb intake work on the 74 head matched to the mt bottom? and will a 75 cr250 rear wheel work on my mt250? ouch and thanks - el

that would be voila not viola - el

Yes the 75 carb will work on the 74 CR250 intake manifold. The 75 carb is very similar to a 74 CR250 carb. And yes a 75 CR250 rear wheel will fit an MT250 just use the CR250 wheel spacers to be safe.

jerry - thanks for all the help - el