Hey guys, does someone have the official specs of the 1976 YZ 175? Especially looking for HP and torque statements. Thanks! 

I collected a lot of info over the years on the YZ175c...  One thing to know is the cylinder stud spacing and engine cases are unique to the YZ175c...  you cannot just bolt the cylinder/head onto any other cases. 


 

The 125 and 175 are interchangeable. Got the same stud pattern plus same con rod. You can upgrade a 125 by changing piston, cylinder and head without removing anything else. 

Hmmm, shutup 'me'--too late & shouldn't stir the pot but looks like YZ175 "76 is different going by base gasket on 'that year' YZ175. Is that what [Mark said anyway]. Checking the three links & the drawing make it clear as well as the part numbers.
Well--head too. Looks wider at the rear studs, wider reed block i guess plus added & extra head stud because of 'that'.
That'd make a great little motor. Are there many around. Was it a popular model or not because no racing class for it.
Be a great trail bike.
www.partzilla.com/catalog/yamaha/motorcy...case-cylinder-yz125c
www.partzilla.com/catalog/yamaha/motorcy...c/crankcase-cylinder
www.partzilla.com/catalog/yamaha/motorcy...x/crankcase-cylinder

Not sure about the 1976 125, I‘m running a 1974 125 and it interchanges with the 175, which is a 1976. same base gasket and everything. Common upgrade back then. 

Yes, YZ175c is a one off with wider stud pattern and ports. You can normally change the 125 to a 175 but this swap is one of the exceptions.

The other notable exception is the 77-79 IT175... the short stud bolt pattern is the same as 78-81 DT125/175 and YZ125 of that era... BUT the IT175 transfers are much wider and only IT175 cases will work without welding and machining.

You can use a 77-79 IT175 head on a 78-81 DT175 if you've modified the DT porting enough to require the smaller IT175 combustion chamber.

Italjet, you snuck in while I was posting...  Yes, a 1976 DT175c cylinder and head will bolt on to your 1974 DT125.  (you lose the oil injection port in the base of the cylinder though... 1976 DT175c was first year oil was injected into carb) 

A YZ175c cylinder and head will not just bolt on to your DT cases. 

Hey Mark, I‘m running a Noguchi kit, which can be used on DT, MX and YZ from 1974. They offered both, the 125 and also a 175 version which is basically the 125 cylinder just with a larger bore. I can swap between the cc by just taking the 125 or 175 cylinder kit. 

Italjet,

You specifically asked about the 1976 YZ175c.

You can swap cylinders and heads around between the 1969 to 1976 Yamaha AT, CT, DT125, DT175, MX125, MX175 and YZ125.  (All were the "long stud" type). 

Depending on what you start with and what you're swapping to you might only need the cylinder and head...  or you might need a manifold and possibly carburetor as well.  For example you could install a 1969 CT1 cylinder and head on your 1974...  but the 69 is not a reed valve engine so intake is different.  Or the 1975-1/2 YZ125C, 1976 YZ125X, and 1976 MX125C used a larger reed valve bolt pattern than the other reed valve models in this list.

And yes, Noguchi made aftermarket cylinders and heads that will also fit the above models. 

Yamaha made the YZ175 model for only one year, 1976.  While it was also a "long stud" engine, the YZ175 cylinder and head will not simply bolt on to any other model.