125-200cc Wr125 head differences

Some queries -

1) Whats the difference between 06 - 08 head and 09 on .
I know its has 5 ports but what does this mean ? Is it much better?

2) Can an older 144 head be used on the newer engine?
eg If i was to upgrade to 144 and take it of when selling can it be put on the newer bike

3) With the OEM 144 kit are they abled to be increased to 167 and how is this done ? Stroking or just bore size. ( I guess this is the advantage of OEM kit)
one more-
4)Do the modified powervalve spring kits work on the older motor?
Thanks

Rock Dancer,

1) The heads are essentially the same. The cylinder on the older 125's has an extra bridge in the side transfer ports. I am sure there are small flow advantages to the more open transfers on the later cylinders.

2) Yes the older cylinder bolts right on and visa versa.

3) The newer cylinders can not be bored out to 167 like the older cylinders. The 58mm bore of the new OEM kit is about it for bore and you would need to stroke it to gain more cc's over the 144.

4) The power valve springs work for 02 and later 125's. One note is that it seems that the 125 likes stiffer springs than the 144 and I guess this should be pretty intuitive. My 144 likes the lower and slower opening power valve much more than a number of 125's that guys have tried them on. They still offer the ability to smooth out the hit on the 125 with the inner spring.

I also think that you need to adjust the sealing edge of the power valve when you do the 144 kit. It needs to only be about 2mm wide from the top and if they only regrind them for the extra bore the sealing surface will be much wider and actually lower. You will be stunned by how well the 144 runs on the low end and mid-range when you adjust the power valves sealing surface as well.

Walt

Thanks Walt - I was hoping you would respond - I am sure this is useful information .
Theres no stopping me from getting that 144 kit in the near future.