flynfrog.
we are starting with a YZ250cc yamaha which was originally a 5-valve head and we may or may not go to the 450cc version or skip it and go straight to the car engine.
I commend you for picking a tough target to beat that is a really good little engine. I would be interested to see if you can keep up with the modded engines? Or the 2 strokesrotaryvalveman wrote:Yes I do mean the YFZ 250. I real nice little engine,,, for a poppit valve.
If I can achieve half of what Watson did in his life time I will be happy. I have found it interesting reading also.
how does this compare with setting the valve lash on the stock head? I know it needs done fairly often.rotaryvalveman wrote:well, not quite but not far off.
The base of the head stays in place so the head gasket is not disturbed but the top of the head comes off of the bottom. The head bolts are under the rotors as has been seen. the cap of the head covers the rotors to form the other half of the rotor housing. a simple rubber gasket in a mchined slot is enough to isloate water and the like.
split the head, pull the rotors, change the seals and put it all back together.
I am going to see if we can make it a quicker change but once every 50K Miles is not going to be much of a drama.