'04 YZ250 Vs. '05 YZ250

[maddog1927]

So what changed with the motor from '04 to '05 on the YZ250? Bore and stroke seem to be the same. It the porting different? Or something else? My buddies stock '06 has tremidous power. I am trying to figure out why.

 

[oldfrt613]

It's my understanding that the motor is basically unchanged. The changes are in the chassis. Both ours run about the same, but we have done some jetting ( pilot change if I recall ). The new one is lighter and "feels" crisper.

 

[DLHamblin]

So what changed with the motor from '04 to '05 on the YZ250? Bore and stroke seem to be the same. It the porting different? Or something else? My buddies stock '06 has tremidous power. I am trying to figure out why.

How many hours on your top-end? His '06 just may be "fresher".

 

[Dino Y]

Yamaha has the same engine unchanged for 4 years. After all it's a very good engine.

 

[Matt Fisher]

The pipe did change halfway through the 05 year, and is an improvement.