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TZR125 Track Bike > Cylinder/Head Changing's

There is not much know about the differences between the Y-1 and Y-2 cylinders on a TZR125 4DL engine
But it looks like they have a 1,5HP differences between them.

What I can measure, it seems that the Y-1 has a slightly aggressive port timing
Its more in the 1,0mm's then in the 1,0mm's

Here you have the Y-1 and Y-2 cylinders

Here the Y-1 cylinder
You can see clearly the port's have been reworked

This is relative common by a fresh hone.
But this is done at the factory, as it is a stock piston

Here the Y-2 cylinder.
You can see clearly the port's have not
been reworked

This one uses the first oversize piston.
So logical the oem made work is gone

To see if could find a differences between them, made a port map off the two cylinders.
There are many ways to do this, I use the piston to keep the paper on its place.
Make my finger a bid dirty and rub gently agents the paper until it leafs a mark.

After making it a bid dirty, it leafs a nice mark

This is what I found with the Y-1 cylinder

This is what I found with the Y-2 cylinder

Here the difference between a Y-1 and Y-2 cylinder.

It is difficult to say if these differences are good for a 1,5HP.
Measurement that precise are hard to do, but it looks like the Y-1 cylinder has the better papers.

Will see if I can find more info.

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