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PAKDXYZ

426 Valve ?

6 posts in this topic

I just checked my valves today, all were within spec but they all were near the limit on the tight end, I am leaving them for now, my question for those with experience with this is 1. Will I be ok untill next winter with them like this( I ride an average of 6 or 7 hours a month and its all trails, no track). And 2. Next time I check the valves I plan on adjusting them regardless, would it be a good Idea to replace the valves and have the seats done being I dont really know the history of them. Thanks

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I just checked my valves today, all were within spec but they all were near the limit on the tight end, ...
That's how they were built originally, and it means that they very likely have not moved at all.

As to how much longer they will stay that way, I'm afraid there's no way to know for sure, and nothing that you can really gauge it by. The reason is that neither the seats or the valves really wear much at all in a YZF. You did not mention the year, but if it's an '01 or '02, it has titanium valves in it. Titanium can't be hardened effectively without making it brittle, so the faces are hard coated, usually with a titanium nitride derivative, which is exceptionally hard and long wearing. The trouble is that since the coating is so hard, it can't be easily ground or machined once it's applied, so it's applied in very thin layers, often less than .01mm (.0004"). Once the coating wears through, the valve wears very rapidly, and will sink to less than zero clearance in 4-5 hours or less.

What this means is that unless the seat wears, any reduction in valve clearance usually means new valves are needed in short order. The way to know is to shim, then follow up with a clearance check after the next ride. If it has not moved, it may have been seat wear, and may be OK. If it moves again in one ride, it's a bad valve.

As I say, because the coating is so thin, there is no way that I know of to predict when it will wear through, so you just have to take your best guess, or wait for something to happen.

BTW, the 2000 model used stainless valves, and these can be used to rebuild the '01/02 head if the springs and retainers from the '00 are also used. The advantage is that they are far less expensive, and they last longer after they begin to wear.

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What is the disadvantage to using the ss valves. I have an 01 426 that I'm redoing the top end on. The valves were very tight some of the any way(exhaust <.03 and .2) intake (.09 .06 .15). I don't know what they look like yet. I'm waiting on a spring compressor. If they are worn through will I be able to tell visually? I'm breaking the bank with the parts that I've ordered already if I have to replace the valves I may be in the dog house if you know that I mean. I may have to replace the with ss for cost reasons. Thanks

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There are no practical disadvantages for your type of riding. I can tell you right now at the clearance you're showing that the exhausts are likely shot. The center intake most likely, too. Visually, any wear you can see is too much.

Order from somewhere like the TT OEM Store. You'll save a lot over retail. The stainless valves are $13 each for the intakes, and $30 for the exhausts instead of $85 and $95.

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There are no practical disadvantages for your type of riding. I can tell you right now at the clearance you're showing that the exhausts are likely shot. The center intake most likely, too. Visually, any wear you can see is too much.

Order from somewhere like the TT OEM Store. You'll save a lot over retail. The stainless valves are $13 each for the intakes, and $30 for the exhausts instead of $85 and $95.

When replacing the Ti valves (and springs and keepers) with SS, do the guides need to be replaced as well?

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