Well I pulled my head down last night and sent it to a couple of machine shops today to have them look at the port work and see what they could do. They all said the port work was great and that there is very little to be done to it. The intake ports run straight onto the valves with no humps or bends, really looks like this was designed well from the factory. I called sparks racing to get a second opinion and they said porting that head is only good for 1-2 hp. So I am going to bag the porting mod and just put in my 13:1 piston when it get here. By the way a lot of people are worried about the cam mod making it harder to start because it messes up the automatic decompression release, well there is no decompression release on this like the bike has. It has a plug where you could probably add it but it does not have one. So it will not affect the decompression system. The engine is very easy to work on and the piston will be a snap to put in. It only took me 1 hour last night to pull it completely down. I will let you know if the piston was worth it or a waste of money. I hope the darn thing comes in soon.

 

Thanks for the info and keep us informed on the 13:1 piston. What fuel are you going to use, I heard that 91 is ok.
Also if there isnt a decompression release like the bike does it have a decompressor??

 

I am going to run premium fuel with a 30% mix of 110 trick. Not sure what your asking on the decompressor. It has no kind of decompression release, just a plug in the head where you could put one.

 

The reason the plug is in the head for a decompression valve is because Yamaha sells a kickstart for the YFZ. That is also why when you turn on the key the lights don't work like they do on the Warrior. Everything runs off the stator. You install the kickstart and decomp valve and lose the starter and battery and about 9 pounds of weight.