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srhines67

Question on 426 Valve adjustment frequency

9 posts in this topic

I got lucky and got ahold of a 426 with only about 15 hours on it. It was like brand new. Anyways, I had the valves adjusted at 25 hours and the shop said that 2 of the valves were a hair out and needed adjustment.

I rode for 26 more hours and took it in for another valve adjustment. This time the 3 intake valves were about .05 mm out and needed adjustment.

Anyways, the bike runs fantastic but I don't want to spend a fortune on valve adjustments. I change oil / air filter pretty much every ride.

I have read other posts where guys ride these things for years and don't do any adjustments at all. So, is there something wrong with my bike or my shop or is .05mm really nothing and I am wasting my money.

Solid feedback is welcomed here.

Thx in advance.

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Learn how to check them yourself, make sure they're not screwing you, because they figure if you brought it in in the first place then you won't go home and check them yourself. It's easy, all you need is a set of feeler gauges, and you're set. It's about a 20 minute job. However if they do need adjustment it can take a few hours you're first time.

I assume you don't have a manual for you're bike? If not, buy one, everything you need to know is in their! It will save you ton's of money on the shop labor and parts.

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Anyone else care to share valve adjustment intervals and what worked for them. I have read in several places that valves weren't adjusted for over a year and didn't move out of spec. I'm just wondering why my bike seems to be so special.

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I check them every 60 hours...Last time , no adjustment was neccasary..

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I would check mine fairly often, but never needed an adajustment for the first 2 years.

06 YZ450F

02 YZ426F

06 TTR50

01 PW50

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Sounds fishy to me. I had over 200 hours on my 2001 yz426f before I ever had to adjusted the valves and I checked them frequently. Learn to do it yourself, it is very easy to do. Valves that need to be adjusted frequently indicate that dirt is getting into the motor,check your filter and air box immediately.

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All YZF's from '01 on have Titanium valves. Titanium is a fantastic material, but there isn't anything that can be done to it that will make it hard enough to serve as a valve face, so the faces are coated with a compound like Titanium Nitride. TiN is hard enough. In fact it's one of the hardest metallic compounds known, even harder than carbide, but because of certain limitations involved, the coating is also very thin.

As a result, the normal wear cycle of Ti valves is to sometimes settle into the seat very slightly in the first 10 hours, and then go for a very long time with no measurable wear at all. In the case of the YZ426/450, this can be 3 years or longer. However, once that coating finally wears through, the valve begin to wear rapidly, and will not hold clearance for more than 5-10 hours.

Once the valves reach that point, they need to be replaced ASAP. Continuing to run them in this state wears the seat. Furthermore, if the valve face does not wear absolutely concentrically, the stem will twist and bend slightly each time the valve closes, and can cause the valve head to break off. "Disastrous" is a barely adequate adjective in that situation.

So if you have valves loosing clearance at an accelerated pace, check them frequently, and replace the set after one has reached the point where the shim is .20mm smaller than it originally was.

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I change my oil about every 4 hours of riding time - sometimes 6 - and change my air filter every ride. I don't think any dirt is getting in as the intake side of the air boot is always really clean. But, getting the report that the valves were .05mm out the last time is a little disconcerting. It really doesn't make sense to me at all. My bike only has about 60 hours total at this time.

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