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YZERIK

Dropped valve

14 posts in this topic

hey gang, recently i dropped a valve on my 03 YZ 450f

Im starting the disassemlby and am wondering if i should re-assemble back to stock or if theres any not too expensive tricks/ items i could put in there while im up there. thanks for your time.

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i have an 06 and switched to stainless steel valves from faction mx, and i added kibblewhite dual valve springs. the stainless valves are more durable but u have to upgrade the springs. i spent about $360.00 on parts not including the cost of having the seats cut...

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... the (Kibblewhite) stainless valves are more durable ...
This point is debatable.

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i had problems with the valves "tuliping" and pitting occuring between valve and seat. i know its caused by dirt. i live in the dust bowl of arizona. i know the titanium is a softer material.

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Titanium is softer, but that is why all Ti vales are all coated with materials such as titanium nitride, a ceramic that is off the Rockwell C scale at something over 90. The principal difference is that OEM Yamaha valves will not show any noticeable wear for a very long time, then suddenly become badly worn, whereas a steel valve will wear more continually over the same period. This is due to the coating on the Ti valve wearing through into the base material. There is not a great deal of evidence that steel valves actually last longer, though.

Where and by whom are the Faction MX valves made?

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OEM Yamaha valves are proven,its a no brainer. I think it is either NCY or Yamaha of TROY that has a kit on ebay,comes with 5 valves, springs, seals,for 297.00.This would cost you about 450.00 regular.

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ive had alot of problems with the stock valves. i live in the desert and it seems no matter how good u clean and oil the filter dirt still finds its way in.

the dirt pits the coating on the titanium valve.

Ive heard the stock valves are actually a 2 piece design, titanium head and steel shank?

im not saying the stock valves arent good, just arent suitable for my riding out here in the mohave desert.

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Ive heard the stock valves are actually a 2 piece design, titanium head and steel shank?

Except for the part about the bimetallic construction (they are all titanium be cause you cannot directly weld ti to steel), this is true of all but a very few of the most expensive valves made for anything. One piece valves are very rare.

I ride in the desert, too, 90% or so of the time. If there is a dustier place on the planet than the Imperial Valley desert, I don't know where it would be, especially back in the pack with the old guys. So far, no trouble with valves.

But, if I could find a set of SS valves that were equal to the quality of the OEM steel used in the 2000 YZ426 for a reasonable price, I would use them as a replacement if it was ever needed.

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just pulled it all aprt, and i have 2 bent intake valves.

now the head is true and so is the barrell, and the piston is mint

now can i reuse this piston? its new from my last rebuild in january/08, and upon visual inspection is mint...?

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I don't recommend reusing the piston. The impact and force of bending the valves may have distorted the the skirt enough to be significant without it being visible, and/or cracked the piston. I don't think it's worth the risk.

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as long as there are no cracks i dont see why not. check the valve guides for damage the bent valves could have cracked the guides. how did the valves get bent? the timing jump?

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as long as there are no cracks i dont see why not (reuse the piston).
Pistons are, for one thing, NOT a straight cylindrical shape. They are "cam ground" into something roughly barrel shaped, looking from the side, and from the bottom, oval shaped, with the widest point of this compound shape being at the front and rear of the skirt, about level with the wrist pin.

When the piston struck the valves, a force was applied to the piston that tried to rock it rearward in the bore. This force is primarily borne by the exhaust side skirt, and may well have bent it imperceptibly, yet enough to lead to trouble. Remember that the clearance on the piston skirt is only about .002", and the slipper design has very little skirt to stabilize the piston anyway, so it wouldn't take much to be a problem. It might be OK, but I would not risk it.

Good point regarding the guides, though. :)

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hey gang, recently i dropped a valve on my 03 YZ 450f

Im starting the disassemlby and am wondering if i should re-assemble back to stock or if theres any not too expensive tricks/ items i could put in there while im up there. thanks for your time.

go to www.cyclepartswarehouse.com cheapest anywhere :) 350.00 tops if you replace whole top end

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