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rufusz

Need answer fast : 5JG-121xx-00-00 valves are steel or Ti?

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Hi

The 5JG-121xx-00-00 valves (retailing at around 70$) are Ti valves or Steel ones? (Looked on troy for 2002 YZ426F).

I have to buy new valves today and don't know which ones to buy.

Here Ti valves are at around 200$ while steel ones are 30$ :thumbsup: So it's a major difference and don't know if it's worth it. I have to replace 1 exhaust , 1 intake valve, the rest are ok. How to check if those (the rest) are steel or ti valves?

Thx

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Well, they're stock OEM valves, that makes them ti for that year, 2000 was the last year of SS valves.

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Those are Ti. 5BE .... valves would be SS. Ti is lighter, allowing lighter springs to be used, reducing the overall load on the valve train. Ti also handles heat very well.

In YZF's ti valves last a very long time (if the seats are finished right). However, because of how they are made, relying on a hard coated face, their service life comes to an abrupt end once the coating wears through, and they need to be replaced at that point. Steel valves can wear measurably and continue to be used.

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That is why Ti valved Topends go without warning - the coating is so thin, that valve clearance will be in spec even if the material wore off, and then the wear on the valve happens so quick you lose the top end without warning.

Hey Grey - how does the coating hold up in the valve guide with the continual up/down rubbing in the guide - I know it gets some lube, but if it does wear off, should valve stems not be inspected relatively regular too?

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I've never seen a YZF with any significant wear at the valve stem, and even valve guide wear is rare and usually very small. This is mostly due to the fact that there is no lateral load placed on the guide/stem by the design of the valve train, as there is in engines using rocker arms or pivoting followers. It's not really a factor at all.

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