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swap meet mystery bike

gurt

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Feb 25, 2006
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#1
I recently picked up an old yamaha from the mid ohio swap meet that I hope to have ready for the motocross next year. the problem is, I am having a really hard time figuring out exactly what it is. I was told that it was a 1976 but other than that the guy I bought it from had no idea. It has white plastics and tank, the tank says 125 but the cylinder is marked as 171cc, it has an odometer or speedo pickup on the front hub, twin shocks, it's not oil injected, the carb is a 34mm mikuni, the head has 2 spark plug holes, the frame and engine number is 565000445, and upon pulling the flywheel it has points and a lighting coil. I have looked around for a while online and can't figure it out. Any help would really be appreciated.
 

DougRoost

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#3
The twin spark plugs makes me think it's not a DT...did the MX's have that type of head?
 

BadgerMan

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Jan 1, 2001
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#5
1976 MX125C

Cool bike!
 

gurt

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#6
Were the 175 cylinders interchangeable with the 125 bottom ends? The way the pipe fits and the good compression just seem to be too good to be true to me if thats not the original top end.


-thanks everyone for the help so far :nod:
 
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#7
gurt, yes the bottom and top ends were interchangble. It really sounds like a IT175 top end, a DT frame, YZ125 tank, IT carb, and thats all i can come up with.
 
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#8
Don't think it's an IT175 top end...the IT175 engine sitting in my garage has a RADIAL FINNED head.

Both of my 175's ( DT175, CT-2 or 3? ) have a dual plug head.

It doesn't look to me like a DT frame...the shock mount doesn't look like the right position.

I think it's indeed a 125 MX, with a 175 top end. :nod:

Maybe a Yammie dealer could tell for sure from the serial numbers?

Rotor
 

BadgerMan

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#9
It's a 1976 MX125. It appears that some one has put a DT175 top end on it. As said above, it is not an IT175 top end as they had a different fin pattern.

The 1976 MX 125 was the only MX model they offered that year along with the monoshock YZ's. It was a one year model that was different from its predecessor (the '75 MX125) which had straight up thermal flow shocks and a different shaped tank (although the colors were the same).

A friend had one and I remember it being a real nice bike.
 
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#10
I had a '75 mx250 back in 77-78 and it had a monoshock
suspension, radial finned head and the white color scheme
just like this one.
I was sure it was a '75 but have never seen another with the radial fin head or monoshock.

anyone know??? am I wrong about the year??
 

DougRoost

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#11
I remember the monoshocks coming out in the '76 model year as a major debut. This probably was calendar year 1975.
 
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#12
Ok, so one last question. Does anyone know where I can find a performance pipe for it?

-again, thanks to everyone for the help.