400 SS valves in a 426

The poster regarding Hondas was referring to CRF owners mostly, but the issues with Honda's titanium valves bear much more on quality, process, and material selection than on Ti vs. stainless. Apart from that, the specific info regarding how a specific Honda was originally outfitted is not only an improper subject here, the likelihood of getting good info on the matter is simply going to be much better in that forum than this.

The main issue at hand with Ti valves as used in a Yamaha is that titanium itself is not natively hard enough to serve as a valve face. Ti cannot be hardened, either locally or generally, to a point where the wear properties will be adequate for the job without making it brittle. The material does adapt itself very well to extremely hard coatings though, and so various derivatives of titanium nitride are used on the faces. This coating, however can only be applied in a very thin layer. the coating used by Yamaha wears exceptionally well in combination with the seat materials they use, but once it finally wears through, very rapid wear beyond that point occurs, and if ignored, this can lead to a major failure. You have no way of predicting when this point will be reached, it just all of a sudden is.

Stainless steel, on the other hand, is much harder than Ti to begin with, and can (depending on the specific alloy) be hardened fairly well without an important loss of strength. But the snag is that not all SS valves are made with hardened faces. Some are coated just like Ti valves, and will suffer from the same sudden acceleration of wear when the coating finally fails. Valve recession proceeds quite a bit more slowly from that point than with Ti, but it happens at a fairly quick pace nevertheless.

To the best of my knowledge, Yamaha OEM SS valves are hardened.

Just an update. Got the motor back together today. Stainless valves and springs to match. All went together without a hitch. Also put a YZ450 exhaust cam in at the same time. 3 kicks in tennis shoes and it fired right up. No unwanted noises. All is good. Test ride next weekend.:smirk:

Test ride next weekend.:smirk:

I need details :p:cheers:

I need details :smirk::p

PM sent.

Gentlemen:

I recently completed a top end with new OEM SS valves an new OEM piston including a Hot Cams Exhaust cam.

I am experiencing a new ticking noise that i have not heard before. I sounds like it is coming from the head and in particular from the exhaust cam area and sounds loudest in the exhaust header.

Could this be the Auto Decomp pin contacting the cam follower valves are in spec and the motor makes great power and is running well.

The noise is not terribly loud but you can hear it very well at idle.

Anyone else experience this? I am now on a seek and destroy mission to identify the noise.

A few years back (well more like 4 or 5 or maybe even 6????) I put a Hot Cams auto decomp exhaust cam in my 426. About 30 seconds into the first run the motor locked up. The pivot pin for the counterweight came out and the decomp pin extended at speed. Not real pretty. In fairness it was one of the first auto decomp cams HC made and they stepped right up to reimburse me for the damaged parts. It might be worth taking the valve cover off just to make sure everything is where it belongs.

Excellent info, thank you.

Mark

The poster regarding Hondas was referring to CRF owners mostly, but the issues with Honda's titanium valves bear much more on quality, process, and material selection than on Ti vs. stainless. Apart from that, the specific info regarding how a specific Honda was originally outfitted is not only an improper subject here, the likelihood of getting good info on the matter is simply going to be much better in that forum than this.

The main issue at hand with Ti valves as used in a Yamaha is that titanium itself is not natively hard enough to serve as a valve face. Ti cannot be hardened, either locally or generally, to a point where the wear properties will be adequate for the job without making it brittle. The material does adapt itself very well to extremely hard coatings though, and so various derivatives of titanium nitride are used on the faces. This coating, however can only be applied in a very thin layer. the coating used by Yamaha wears exceptionally well in combination with the seat materials they use, but once it finally wears through, very rapid wear beyond that point occurs, and if ignored, this can lead to a major failure. You have no way of predicting when this point will be reached, it just all of a sudden is.

Stainless steel, on the other hand, is much harder than Ti to begin with, and can (depending on the specific alloy) be hardened fairly well without an important loss of strength. But the snag is that not all SS valves are made with hardened faces. Some are coated just like Ti valves, and will suffer from the same sudden acceleration of wear when the coating finally fails. Valve recession proceeds quite a bit more slowly from that point than with Ti, but it happens at a fairly quick pace nevertheless.

To the best of my knowledge, Yamaha OEM SS valves are hardened.

A few years back (well more like 4 or 5 or maybe even 6????) I put a Hot Cams auto decomp exhaust cam in my 426. About 30 seconds into the first run the motor locked up. The pivot pin for the counterweight came out and the decomp pin extended at speed. Not real pretty. In fairness it was one of the first auto decomp cams HC made and they stepped right up to reimburse me for the damaged parts. It might be worth taking the valve cover off just to make sure everything is where it belongs.

I did have a look in there the valve clearance on the exhaust opened up almost .004" I cannot explain why they opened up so much after the first run. Maybe i had too much assembly lube under the valve shim an it came out when the motor got warm? (since I set the valve lash with the head on the workbench) I was expecting the valves to seat in and get tighter not looser. I will keep you posted. I did take a very close look at the decomp pin and it seems to be workig well.

I did have a look in there the valve clearance on the exhaust opened up almost .004" I cannot explain why they opened up so much after the first run. Maybe i had too much assembly lube under the valve shim an it came out when the motor got warm? (since I set the valve lash with the head on the workbench) I was expecting the valves to seat in and get tighter not looser. I will keep you posted. I did take a very close look at the decomp pin and it seems to be workig well.

I did the shimming on the bench as well but I did check them after I installed the head. On mine the intakes were just a tad tighter but still in spec and the exhausts were the same as on the bench. After some run in I'll check them again but I have to agree I would not expect them to get looser. So were the loose exhaust valves the noise you were hearing?

I wouldn't use assembly lube under the shim, just oil. In fact. I generally use very little assembly lube anywhere, and then just a film of it. My guess is you either had the shim cocked in the retainer or floated it on the assembly lube. Time will tell. Recheck the clearance after a bit to see if it has stabilized.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now