It took over a year of testing and modding....but it is finally done and it's a rocket! I did everything one step at a time so I could record the performance gain every step of the way! The first thing I did was fixed the handling issues with the bike. It didn't turn as well as I had hoped and it didn't go through the whoops as fast and as straight as I liked. Although stock was pretty good....pretty good doesn't cut it with me! While others tried raising the forks up in the triple clamps, changing tires, and different offsets.....I was able to fix both problems with a simple revalve of both ends...I'm not going to go in much detail here but, the bike handles better than any other bike I have ever ridden! With all the handling and suspension issues ironed out it was time to move on to the biggest reason I bought a 450 in the first place POWER!!! The YZ has good power but not a lot of it. I one of those guys who rides a stock 500 2 stroke and says: this bike is kinda slow! I want a lot more! I was pretty sure I was going to be dissapointed in the power department but loved how the bike handled now and had decided to keep it anyway for a moto only bike if neccesary! I could always use my Perimeter Frame KX500 wonder bike to do everything else! The first thing I did was try every pipe known to man and decided to keep the White Brothers Alumi Pro2. This bike added a lot of midrange and top end and didn't hurt the power down low. Other pipes helped the bottom end a tad but didn't come close the the WB in peak power! The next thing I did was contacted www.ronhamp.com (RHC) He set me up with a carb mod. He bored the stock carb to 44mm and some change and modified the angle of the bore slightly to enhance the fuel charge! This added power across the board! I was very pleased at the additional power at every rpm level! It had picked up snap right off idle and pulled with much more authority! This was a very impressive mod! Next I noticed the bike would stall very easy, so I opted for the Yamaha GYT 9 oz flywheel. It is a complete flywheel assembly that weighs 9 ozs more than the stock 18 oz. (for a total of 27oz) This was a big improvement to the overall character of the motor. It pulled harder off the bottom and you could run in a taller gear and not stall out. It did not make the bike rev noticably different it just gave the bike some meat down low and it was now able to chug it tight or slow going! Next I installed a JE 13.5 to 1 piston. This gave the bike more power across the board. It felt much like the carb mod but not as drastic of a power increase. All together now with a slight mod to the ignition timing the bike was coming together and was quite fast with an excellent powerband but I wanted and needed more!!! Next I shipped off the head to RHC (www.ronhamp.com) I left a note tied to the head which read "Dear Ron, please make fast and return ASAP!" I guess you should be careful what you ask for!!!!!!! I AM ABSOLUTELY FLABBERGASTED AT THE RESULT OF THE HEAD PORTING!!! It is truly amazing!!!! : The porting felt like an increase of all the things I had done up to this point...times THREE!!! It is an absolute rocket! It has so much more boost off the bottom and then it just explodes!!! I still cannot believe the power it puts out! It revs and pulls sooo much harder and further and faster it's unreal! This is the funnest bike I have ever ridd'in and now does every type of riding from moto to hillclimbing to desert better than I could've dreamed!!!! It's still capable of trail riding in fact, it's better, you just have to turn the throttle very carefully! It carburates way better and smoother at tiny throttle openings but you better be pointed in a safe direction when you turn the throttle hard! It's perfect!!!! The first victim of the RHC's porting wrath was my good friends Service Honda CR500! He just spent $11,000 on this bike and went with the aftermarket engine building mods. The mods proved not to be enough....my YZ walked it pretty bad. I made the mistake of letting him ride my bike.....now his bike is for sale! BY the way , my perimeter framed KX500 is now been sold! The only bad side effect of these mods are that you won't want to ride other bikes because they will feel sooo weak and boring in comparison. The stock 450's feel like a 250f now...... In conclusion, you can waste your $$$ on a lot of after market stuff and after market places that won't add much if any performance to your bike ( I know I've done it in the past) or you can have a world class engine builder build you a world class improvement! (RHC) Ron Hamp is the real deal!!! A big thanks to FFR (T-DUB) for all you help and getting me hooked up with RHC www.ronhamp.com .