Vintage Dirt Bike Q & A

I recently bought a MT125 and it's a "cafe racer" project for me. You might of read my other post but it's no longer in a MT125 frame. I'm lucky in the sense that I have a salvage yard close to me and i'm there all the time. I'm going to get the MT125 and Cr125 motors that are there but not in the greatest shape to say the least. The price is right for the most part in my opinion.

I already bought a copper head gasket for it. The intake manifold from the Cr125 cylinder was allready taken.. it's ok. But is there any benefits to the CR125M cylinder setup to the MT125 setup? I know it lacks the oil injection setup. The MT125 only had 1700 miles on it so i'm leaving it alone but i'm building quite a few cafe racers so learning these bikes would be good for me. I'm not to worried about gearing right now, but I have a few ideas and once I get a motor to play around with it i'll consider some options including the 6 speed setup.

Anyone build any hybrids like a 125 bottom end with a 250 top end and rod piston setup? Possible?

Curious what are some options?

MT125 cafe racer? Are you familiar with this bike?

http://raresportbikesforsale.com/stocki ... da-mt125r/

The CR125M cylinders - especially the '76-'78 ones - will definitely make more power than the MT ones ever will. The oil injection can be adapted to a CR125M manifold.

The CR transmission will give faster acceleration in the lower gears, but a narrower speed range (i.e., for the same top speed, first gear will be much higher than with the MT tranny).

The MR175 motor uses basically the '76-'78 CR125M cases with a "250-sized" 66mm piston, for 171cc. I guess the motor could also be stroked for close to 250cc, but the bottom end wouldn't last long at that torque level.

Ray

_________________
'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Yes, I was debating building one based on the MT125 but I ended up not liking how I felt on the MT125 frame. The setup i'm building should be lighter, just as strong, and more of a head turner. No fairing but it's very minimalistic. More of a Cb77 type Keeping the oil pump and tank setup possibly. At least for now. I've got a suzuki small gas tank I'm turning into an oil tank cafe ass. I like 60's and 70's bike so all the parts are going to be from that era even if it means custom which so far isn't to too much. It's a mix of Cb, Xl, Cr,Mt,yamaha, and suzuki parts right now. As far as front setup it's a mechanical caliper setup, and there might be one on the rear at some point. I'm in the process of figuring out how to make a Cb front wheel into a rear wheel disc setup with possibly a belt drive. Fun fun. If they let me I'll vintage race it but it's going to make them scratch their heads for a while.

The one catch I was worried about sticking the motor in a different frame was the chain setup. I noticed the front sprocket sat lower and farther away from rear swing arm. I shortened the MT125 chain and took a peak at it. The MT125 sprockets are going to be a bit to close for comfort for me. So I'm probably going up on sprockets. I've got to work this whole weekend but 80% of the kinks on the swap should be done in the next few weeks. It's not a normal motor swap. The majority of the bike is custom from different motorcycle parts. The brake rear set is 50% done but both side rear set mounts are done. I need to source another honda lever setup like the brake setup for the shift setup and that will be done. Front fork setup and brake setup is basically done but I need to figure out what height i'm going to set it at for me like it. The rear setup will most likely be cable operated drum setup for now which is probably the MT125 drum with a 1.40 18 inch rim. Aluminum if I can find one in the states. The custom rear swing arm setup is going to take awhile and it's not a big concern to me but it's based on a cable operated front brake setup.

Do you have any pics of this project that you can post up?

_________________
WWW.CADDY500.COM
The High Performance
Big Block Cadillac Forum

I will, but let me get it to where it doesn't look like a mess of uncertain madness. I'm going to be be building bikes, powdercoating, sodablasting, and a few other things for a living pretty soon. Right now it's a bit of mess in the garage and I might be moving to a shop soon.

I will say it looks proper though

Things are going well enough I bought another MT125. So I'm building two cafe racers hybrids now. One will be forsale.

i got the other MT125. i'll be putting up pictures today of it. It's getting turned into another cafe racer based on another frame.

Parts avaliable

Front and rear wheels with new tires
fenders
Front fork assembly complete
oil tank (possibly)
rear shocks (got two sets, one very nice and one ok)
seat
handlebars
drum arm to swing arm stabalizer (two of them)
pegs (two sets)

If you need parts feel free ask. Something might be avaliable.

i decided to turn one of my MT125 frames and boxes of parts into a cafe MT125R street version. It's somewhat going to be based on the MT125R but a little more retro looking without the fairing and a bigger tank and small rear seat setup. I've been working on it today. Goes well.

As far as why? just to many parts sitting around and i figured why not.. This bike is getting sold when it's done.