06 YZ450 Suggestions for engine rebuild *unique application

Hi everyone,

I got some down time due to track injury and need to do a rebuild on my motor. I read the stickies and even jumped around a bit looking at engine builders in socal, but the application of my 450 is unique.

Bare with me as I know not everyone agrees with converting a dirtbike to a road race bike, however, that's what I did. I'm not beyond doing most of the work myself when I can use my left arm again, but I wanted to get suggestions from some of you vets/pros.

I have a otherwise stock engine with low hours, took possession in 2010 and the engine had about 60-70 estimated with rec riding. I've probably added a brutal 7 hours as the bike sees WOT for periods of about 10-15 minutes. The engine still runs strong with no knocks or pings, but a good check is in order, I'd like to add hi quality parts for longevity's sake.

I don't care for any added horsepower so larger bore is out. What I want to do is basically replace some of the internals with high quality Ti parts like the valves. Maybe I can do the cam as well. I read that a fair amount of you have gotten 100+ hours on the piston so I'd like advice on whether to go aftermarket or stick with OEM? What I don't want is for a catastrophic failure to put me on my face after I heal this time around. ;)

If you have any good experiences with a builder in socal (I'm in the hi-desert area) or advice as to what components I should swap to take this level of abuse, I'd like to hear it. Thanks in advance for any experience you share.

There are no higher quality parts for the YZF than OEM, for the most part. There are some aftermarket valves that are made from a single piece of titanium, but they're really expensive. Likewise, the piston is among the most durable you can find, and unless you go with a higher than stock compression ratio, I'd stay with it. If you're going to raise the stakes a little, I recommend CP pistons. In the interest of longevity, try to get one that uses two compression rings rather than one.

After a bit more research, it seems like I would stick to SS valves. Price and longevity might not make the juice worth the squeeze. I am liking those CP Pistons (I've used Wiseco in quads before), but for my application would you recommend sticking with the stock compression ratio? It seems that Supermoto which is the closest application to roadracing for this beast tend to have a lower CR. (12.5:1>)

Thanks a bunch for your insight!

Raising the CR does have a more pronounced effect on low and mid range than on top, so it may not be something that's worth the trouble.

As far as stainless valves go, I have seen no evidence that any of the aftermarket stainless valves are more reliable or last longer than OEM Titanium. Kibblewhites are a little cheaper than stock Ti, but the required spring set, with its titanium retainers, is so expensive that the whole package ends up costing more.

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