yzf valves vs crf valves?

I am without any doubt, a fan of Yamaha bikes. They simply are more reliable. I've argued it myself many times. I see many many more old YZ's than I see old Honda CRF's. My YZ was a 2000 model and still running strong when I sold it (valves well within spec). I am also an impatient person and somewhat of a gambler so I bought an 06 CRF450. I had fully intended to wait for the YZ in the fall but I didn't. I did all the research I could on CRF and RMZ, and yes, I saw some, but not really that much information on valve issues with CRF and timing chain issues with RMZ. Most of what I read had to do with adjusting the valves (they seem to be out of spec both ways???) and mostly when new. My riding buddy bought a new 05 RMZ 450, and after 5 hours a thin thrust washer behind the clutch basket or hub, somehow came apart and got in between the hub gear and the crankshaft idler pulley and busted the case with $2200 in damage. So, yeah I'm a little nervous. Suzuki did agree to fix his bike (after some arguing) 100% parts and labor. They asked the shop to OVERNIGHT the bad parts to them to analyze. I have another friend whos son's KX250F had to have the valves replaced literally after every race. He couldn't practice it because he had to save the valves for the race. If I remember correctly, he didn't make it through a couple of races. He bought a YZF250. No problems, rides the sheite out of it. I got my bike for $5900.64 OTD which was another reason I didn't wait. So far so good with mine, it handles like a dream and has more than enough power. I'm going to check my valves often and hope for the best. There are actually many more "no issue" stories about CRF's than problems. Anyway, don't beat me up. I had to get something lighter and easier to handle cause motocross at 43 is a little harder on the bod than it used to be and I just want to ride.

One of the things you'll find out about the guys at MXA is that they're pretty good, but they aren't really engine people.

The four valve theory is based on the idea that the larger valves are heavier, and since there are fewer of them they have to lift farther, and thus close harder to allow the same flow volume as the YZF's 5 valves. If that were true, the 450's would wear faster than that 250F and CRF250, and they don't.

Poorly, or aggressively ground easing ramps on the closing side of the cam could be at fault, which follows the same general thought pattern, but using an aftermarket cam in a YZF doesn't seem to shorten valve life that much either.

I still think it's a simple question of quality.

Thank you! Your the best Gray! :D

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