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tech24

valve job question?

10 posts in this topic

Some of you may remember that I lapped my titanium intake valves because I didn't know they were titanium and the service manual is not updated so I sent the head out.

I explained what I had done and thought that I needed new valves. I just got the head back and the only work done was a 3 angle valve job. Maybe there was a misunderstanding. I haven't been able to get a hold of the guy (hes a busy man) but should I run this head? Was this the work I needed or did I need new valves?

Thanks for your help!

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I will assume that you lapped the valves, but did not grind the seats at all when you first did this. In that case, you needed the seats cut in any case, regardless.

The remaining question is, what damage was done to the valves by lapping them, if any? Obviously, there is no way for me to know, but if the machinist noted any material removal from the valve face, no matter how slight, the hard coating was probably compromised, and the valve in question should be replaced.

But lapping will not always harm the coating. It has a real potential to do so, but it won't always certainly hurt the valve. You might ask him what he remembers the valves looking like, and if he recalls that they looked OK, you could try running them. The tell-tale indication of damaged coating is that the clearances won't hold where they are set, and the only thing that might come of all of this is that your valves will last one or two years instead of three.

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Nothing was in real bad shape they has some small leakage. I sent it to CT racing which in my opinion Allen is the best in the business so I guess i'll run it and see what happens. I explained what I did and told him to do whatever was necessary. I don't know that he was the one with his hands on it but I have never seen any unsatidfactory work from them.

Either way I guess it will run for quite a while as im not usually on the rev limiter. Im just dumping a lot of money into this bike and being particular. Thanks for the input.

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heres the email I got back from Allen in case anyone else has a similar question but sounds like im good to go.

The coating helps add longevity, but it’s not imperative. We are set up to and re-surface titanium valves on a regular basis with no problems. Many or the titanium valves we purchase in oversizes have the coating machined off.

Run it, the valves have flat surfaces and are good to go.

A.K.

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heres the email I got back from Allen in case anyone else has a similar question but sounds like im good to go.

The coating helps add longevity, but it’s not imperative. We are set up to and re-surface titanium valves on a regular basis with no problems. Many or the titanium valves we purchase in oversizes have the coating machined off.

Run it, the valves have flat surfaces and are good to go.

A.K.

That goes against everything else I have ever read, or seen in practice. If this were true, why then would a titanium valve "sink" so rapidly after wearing past the first .10-.15mm in shim size?

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There is a member who lapped his brand new OEM valves on a YZ250F not too long ago. He had to reshim after only a few hours, and by the 20 hour mark was buying new valves again. If the coating is damaged on the valve, it will not last long.

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well don't know a lot of my buddies drag race quads and have had several extremely high performance race engines built by Allen and never an issue with anything so I'm gonna go with what he says and I'll be the guinea pig if you will and let you all know how it goes. Although the bike won't be ready for a bit

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My builder is on the side of needing new valves when the coating is worn off. I have new intake valves on the way.

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My builder is on the side of needing new valves when the coating is worn off. I have new intake valves on the way.

well shit I guess the plus side easy taking the head off is easy and I saved money that I can use for other things...we'll see I guess

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