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aclemac

YZ 450F do they need the oil upgrad like the yfz 450?

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I just got a 03 yz 450f that I am rebuilding with a 478 big bore kit. I have seen many many threads about the yfz 450 needing a oil upgrade because the piston pin doesn't get enough oil. do the yz 450f motors have this same problem? if not, what's different?

Also, anyone know the jetting changes needed to go from stock to the 478 kit?

Thanks.

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This has just sprung up here recently all of a sudden, but you would think it would have been mentioned long before this if it were truly a problem. Of all the broken wrist pins I've only this week heard about, none were OEM Yamaha. I find that somewhat interesting, as is the fact that the info regarding there being a weakness in the oiling system appears to be coming from the manufacturers of aftermarket pistons.

Nevertheless, Yamaha has, if I recall correctly, increased the amount of oil sprayed on the piston, but that was to increase piston cooling, not address an oiling problem. Again I will say, this is the first I've heard of it.

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