I've got an '06 YFZ450 that had the top end (including a new head assy) about 6 months ago. I've followed the OEM maintenance chart for oil changes, valve adjusts, etc. My bike wasn't running right, so I took it to the Yamaha dealer (that I bought it from and has done all the work on it). They say the valve guides are excessively worn in all of the guides. We went to the dealer and the shop manager showed us that there is no blueing of the valve stems and no sand (we ride the dune up here in Oregon) in the motor. He says that this appears to be "premature wear" and that he hasn't seen anything like this before. The warranty company says it's from "hard riding" from riding on dunes and using paddle tires (which make the motor work harder than it should), and they won't cover the repairs. They says nothing's broken. The dealer hasn't been able to convince the warranty company that this is warranty.
Has anyone else out there had any problems with valve guides wearing in 6 months? Have any of you been through this before? Any suggections on which way to go on this?
Thanks, Tim
Eugene, Or.

 

Don't hard working motors make more heat? So if the valves weren't over heated how can they say it was from hard riding? A friend of mine had a 400EX that had the same problem. The head was totaly warn out but the piston/bore were perfect (no signs of dirt or over heating) How do the cams look? If the head ever had a lack of oil pressure the cams would show it. Also, you said the top end was replaced 6 months ago? So the second head is the one that you had problems with? My guess is someone didn't do a proper valve job when they built the new head. I have seen people cold remove and press value guides without reaming them... the correct way in a chevy 350.. but totaly wrong for 99.99% of motorcycle/atv motors. Sometimes they order the head pre-assembled from the factory for warranty work so that might not be the problem.. I would ask them how the last head came, if it was pre-assembled or not and ask how they installed everything.

 

Are these YZF's high maintenace too like the TRX450R's are said to be?