TY / DT 175 heads

[hot101rod]

In looking at the Yamaha spec sheets for the 1975 TY175B and DT175's, the DT has a slightly higher compression ratio. The DT175 head has 2 spark plug holes and appears to be the reason for the higher compression ratio. Could I find a DT head to simply raise the compression ration on my TY? That way I could just change it back to the stock head if I didn't like it.
Thanks in advance.

[David Lahey]

The DT75 head gives higher compression because the volume inside the head is smaller than in the TY175 head.
Yes a DT175 A,B,C or D model cylinder head will fit to the TY175 cylinder.
Depending on what exhaust system you have on your TY175, you may need to trim down some fins on the DT head for clearance.
If you are interested I can probably post up comparison photos of those heads.

[Kurt]

Interesting topic, a higher compression ratio could help the Achilles heel of the TY175 and increase the low bottom end torque.

Compression Ratios listed
TY175 = 5.8:1
DT175 = 6.8:1

Modern bikes hover around the 10:1 mark I believe.

[PA]

You could always shave your head.

TY175 Head Shaving.jpg (289.37 KiB) Viewed 8712 times

[Kurt]

Also based on the bore and strokes if you added the DT175 head to the TY175 you would be increasing the compression ratio higher than that of the DT175.

Bore and Strokes listed
TY175 = 66 X 55mm
DT175 = 66 X 50mm

Based on my calculations you would end up with a compression ratio of 7.5:1 if you added the DT175 head to the TY175.