KX Guru Racing

Thanks goes to Doldguy for providing these numbers
KX 500 with 86mm Stroke, 145mm Rod Length

Exhaust Timing Opening From “TDC”, Not from the deck but from the piston ( 0 deck height.)

200 Degree Duration 41.855mm
198 Degree Duration 42.633mm
196 Degree Duration 43.409mm
194 Degree Duration 44.183mm
192 Degree Duration 44.955mm
190 Degree Duration 45.724mm
188 Degree Duration 46.491mm
186 Degree Duration 47.254mm

Here is a link to a calculator

https://lambretta-images.com/tuningh/po ... lculators/

4-28-20

Well... It seems I have been deceived by the Clymer Service Manual.
The manual says that the 86 KX500 exhaust port timing is 192.
It is not.
I have two 1986 cylinders in my shop.
They both measure 184 degrees with a .020" Base gasket.
Which is what they claim for the 1985 KX500.
The 1987 came in at 183.
I don't have a 88 cylinder but I was told that it measures 184 degrees
I may be making other changes to this chart as well but for now it is what I have..

85 KX500 piston dome 14.5cc??
If that number is correct you would need to lower the deck of the cylinder .098" to use a flat top piston... hmmm...
Need to double check my math.