I would like to post all my recent troubles with my YFZ in case anyone out there has one. First, the motor seized due to lack of oil to the crank and rod while up on the back wheels for too long. I had the rod replaced and had the oil mod done. I then put the bike back together and foolishly didn't follow the re torque instruction exactly as some of the steps seemed unecessary, a buddy said he always just tightened the head bolts really tight in an X pattern. Well, i can tell you the head gasket will blow or you will pull air into your cooling system causing overheat everytime. Most mechanics will focus on the cooling system and then check the jug and head for warp and everything else while all along its just improper torqueing of the head bolts. I got the bike running great again but has about 2 weeks of head scratching first.

didnt yamaha get some of those bugs worked out in the 07 and 08 models? (I hope

Yes in 07 and up they did add a oil mod into the motor assy.
As far as the TQ sequence always fallow the manual.

yep, im fact, you can install the 07 and up oil system on the older models.

bummer, i just had the hole drilled that sprays a fine stream directly on the rod

it works great, i can wheelie all day long without fear of wallet leakage

i have this 2006 yfz450 i bought a new battery but when i get done rideing the battery is low i got to charge it every time any body know what may cause the problem.

Check with xtrmsuperman..........I believe he is having the same problem and has narrowed it down.

Kray I have done some digging on this exact problem for other members, it is definitely that the factory YFZ did not have enough charging power to keep the battery maintained, especially with alot of start and stop riding. I think your only alternative is to either put in a higher watt stator/cdi or to do a battery box mod and put in a bigger battery. I found this page with some great info and pics, might be a good start for you

http://atv.off-road.com/atv/article/articleDetail.jsp?id=192624

I have a few friends who ride these and one of them was told that on the ones up to 07 you have to ride with your headlights on. That is how the battery charges. I know it sounds stupid but none of them have battery issues anymore. Hope this helps.

I agree with Brandon, a buddy of mine has a 2004 YFZ, he was told also to ride with headlights on all the time. it seems to work.

I wonder if there is some defect in the stator or CDI that tells the computer not to charge unless the system is "under load"?

I bet the charging circuit is in series with the headlight therefore if no power returns through the common no power is applied to the rectifier.