Vintage Dirt Bike Q & A

Ok, stupid question what makes these model different? Frames? Shocks? Motor?..I have just been given the task of restoring a 1976 MR and will need to find parts.


John

The CR is for motocross, the MR is for Cross Country/Enduro and the MT is for street/dirt dual purpose. There are many differences between models. People on this forum will be glad to answer any questions you have as you go through your restoration. Good luck with your project!

I have an MR250 I bought new in 76. Whats wrong with your bike?

The seat and gas tanks, brakes, and wheels are different too. You can check out pictures at http://100megsfree4.com/honda/ since mine may have had some parts substitution that confused me.

I haven't got out my calipers to do measurements but it looks like other then the crank and flywheel some of the engine parts like cylinder and piston may be interchangible.

The MR and CR may have the same frame geometry, Im not sure, but I think the CR frame is chromemolly. I think the CR has a plastic base seat. I know the front wheel is different, but what about the rear wheel? What about the airbox on the MR and CR?

Has anyone ever ridden a CR thats had a flywheel put on it? If I put a CR cylinder on my MR or had it ported do you think it and the "Flywheel CR" would be about the same? The only difference would be the gear ratio. What Im asking wonder wich engine would be best for enduro-trail, a "Flywheel CR" or an MR with CR cylinder. I remember reading in the mags that the MR's had screwy gear ratios.

I would like to rework my MR with maybe CR frame and other parts to lighten it up and give it more power. Might be best to just start with a CR and put on flywheel and big tank.

Hope this post is not too confusing.

Unless you have access to the parts you mention, it might be easier to start with a bike that closer matches your needs.

_________________
'84 Honda CR500
'84 CR125
'85 KX125
'83 IT490
'82 Maico 490
'80 YZ465
'75 Husky CR360 GP Mikkola
'75 CR250
'72 DT2MX
'91 XR200

The MT250 models are based on the 73-74 type CR250 sharing frame geometry and several motor parts. The MT is the only Elsinore model with oil injection. The top ends of MTs and 73-74 CR250s will swap for example.
The 76 MR250 is based on the 75 CR250 sharing many parts, frame geometry, etc. The MR250 top ends will swap with 75 or 76 CR250s. The MR250 was detuned with heavier flywheel, lower exhaust port height and baffels in the pipe for noise among several other things. I have had one for years. It is heavier and slower than my 75 CR250 but it is also quieter and is a great bike to teach people how to ride with. I beleive they are worth restoring for a fun trail bike but not worth trying to get max performance like a CR250. If you want that it would be easier and cheaper just to find a 75 or 76 CR250 and restore it.

I agree with all earlier post! It's a great bike, but a CR has a much stronger pulling motor.

A CR seat will fit, but it's shorter in length, and the plastic (vs steel) seatbase does not have a cavity for the airbox top. Simple to fix, unscrew the baffle.

Tanks will swap easily, but use different petcocks.

CR points will not ft the MR, nor will the flywheel puller commonly listed as (CR, MX).

MR footpegs are taller, and need the taller brake pedal to have everything line up.

Many parts from a 75-76 CR will bolt right on. Little things like brake and shift pedals, the brake 'levers" on the hubs are aluminum, vs steel, resultiing in the CR being much lighter. Cr frame is also slightly lighter, but it's the sum of all parts that make the biggest differences, weight wise.

Overall, the CR and MR are much closer than the MR is to the MT. Have fun!

Well, both side,cases were off Clutch spring are missing, clutch plates look burnt,spark plug was left out and the bike has been stored outside for three years, missing all the sidecase bolts, right side sidecover,besides that, it is all there. Also seat is torn badly, tank has a big dent in the upper corner. Let say this is just shy of a basket case!

Ouch

_________________
'84 Honda CR500
'84 CR125
'85 KX125
'83 IT490
'82 Maico 490
'80 YZ465
'75 Husky CR360 GP Mikkola
'75 CR250
'72 DT2MX
'91 XR200

Well, I have had a very interesting week, since I last posted the condition of my resto project, I have found most of the parts are salvageable, found a complete clutch assembly on Ebay, fork seals, complete gasket kit and the all important 'Shop Service Manuel" The one part that is shot is the rear wheel, the rim is bent and has a crack along the rim. So if anyone has a line on rims or know where a replacement could be had please let me know. I'll update with pictures this week.

PS Keep the comment coming


thanks
John

The original MR rims did seem to be a little soft, cracks and dents are pretty common. I've had a slight crack in mine for years, I keep an eye on it, it's held tight all those years.

I have a spare set of "used" wheels in case i need them, you can find them if you look around. Rear wheel is the same aaas the CR, front is not, due to speedo drive 7 hub.

Sound like you are having fun, keep us posted on the progress and discoveries!

I want to thank everyone for all the info about mr's. I just bought one last night and wasn't sure of "what" I had exactly. I got outa bikes in 75( when I bought my first car) and just recently wanted to get back. I was looking for something to trail ride with and feel (now)that I made a good purchase. It doesn't run, has been sitting against a fence for 5 months and has 1/2 a tank of "fuel" in it but, I think I have found all the help I'll need right here to get the old girl in the dirt by this spring. Thanks.