Jump to content
Sign in to follow this  

Exhaust valve clearance tight. High mileage. Now what?

Recommended Posts

I checked my valve clearance the other day and, lo and behold, my exhaust valves were at .006". Intakes are fine. I probably have close to 4000 miles on the bike. Every other time I've checked them they were fine. My question is - does this mean a valve job is imminent or can I hope to reset them and motor on for awhile? Has anyone been down this road?

Yeah, I know, there are lots of threads on the valve issue, but I could find none that applied directly to my scenario. I feel a little sheepish as I have posted a number of times that my valves were no issue. Honestly, they have put in some pretty good service and this is the first sign I've had of a problem.

Share this post


Link to post
Share on other sites

I know I can shim them back to speck. I guess I'm wondering if, after this many miles, shimming is going to do much good. Are they just going to quickly tighten back up. Am I likely to be looking at a valve job?

Share this post


Link to post
Share on other sites

If you have never shimmed then shimanf check again in a few hundred miles. If the tighten up again ten valve job time if not.....they are fine, and allt questions are not needed

Share this post


Link to post
Share on other sites

I have heard over and over that once they start to move the end is near very soon.

I would start saving or buying parts.

Share this post


Link to post
Share on other sites
I have heard over and over that once they start to move the end is near very soon.

I would start saving or buying parts.

This is kind of what I've heard also. I just wondered if there was anyone who had actually been down this road or is it all a myth. So much of the stuff you read on these forums is just people talking, without any first hand knowlege. I'm obviously going to reshim them and hope for the best.

I'll report back on what kind of luck I have :thumbsup:

Share this post


Link to post
Share on other sites

Seeing that the exhaust valves are made from steel and dont have a coating on them, I wouldn't think it'd be necessary to go tearing this engine down. Re-shim and the bike will likely go for a fair while yet. It is however true that when the intake valves (titanium) get out of spec, the titanium hardened coating on the valves has worn off which means that replacement is imminent. The softer underbelly of the titanium valves will simply not hold clearance.

Share this post


Link to post
Share on other sites
This is kind of what I've heard also. I just wondered if there was anyone who had actually been down this road or is it all a myth. So much of the stuff you read on these forums is just people talking, without any first hand knowlege. I'm obviously going to reshim them and hope for the best.

I'll report back on what kind of luck I have :thumbsup:

This is the info I get from a couple of people that I respect (not message board info) that actually work on engines.

When the coating on the valve goes (initial movement/tightening)it exposes the soft underbelly (the inner material) and as soon as the soft inner material is exposed the wear speed is intensified.

I unless your valves have been at the spec they are at now for a long time I would expect that a valve job is in you near future. It sucks but I guess it's just the name of the game.

Share this post


Link to post
Share on other sites

Are you sure you were right at TDC? If you're just before it you'll get a smaller reading.

The exhaust valves are stainless and I've heard of maybe 1 failure on the 250 from worn exhaust valves, and even then I don't know if it was true.

There is no coating on the exhaust valves to wear off. Only the intakes, which are titanium and do have a coating on the valve face.

I'm sure they are fine and just need to be shimmed to spec.

Share this post


Link to post
Share on other sites

Yes, I do have it at top dead center. The measurement is correct. Well, it's not correct, but it is accurate.

I'm a little confused, as I thought the exhaust valves were the titanium valves. If, in fact, it's the intakes that are titanium, I feel a lot better. The intake specs are just fine.

Anyway, thanks all for your responses.

By the way, getting the shims out from the exhaust valves is exceedingly easy. Remove the retaining clip that secures the exhaust valves rocker arm shaft. Thread one of the valve cover bolts into the end of the shaft, and pull it out. You can then lift the rocker arm right off. Piece of cake. Use a magnet to extract the shims. The only trying part of this procedure is getting the retaining clip out. Not a big deal though. I haven't tried putting it back in, but, as others have noted, it can be a little hassle. We'll see. It's just kind of small.

Share this post


Link to post
Share on other sites

I'm a little confused, as I thought the exhaust valves were the titanium valves. If, in fact, it's the intakes that are titanium, I feel a lot better. The intake specs are just fine.

http://www.hondanews.com/CatID7643?mid=2005011933336&mime=asc

Like the CRF450R, the roots of the 450X engine spring from a high-tech, liquid-cooled four-stroke layout with a bore and stroke of 96mm x 62.1mm, to yield a displacement of 449cc. But the design element that sets both bikes apart from any other four-stroke is Honda's innovative Unicam single-overhead-camshaft configuration with a separate cam holder that contributes to a notably compact design.

This design incorporates a carburized single camshaft that directly actuates two titanium intake valves. The camshaft's single exhaust lobe acutuates two steel exhaust valves via an innovative forked rocker arm that incorporates a small roller bearing. This roller bearing significantly reduces friction, and therefore wear, so the cam lobe can be narrower and lighter than traditional counterparts. Valve adjustment is accomplished with shims; the intake valves use a direct shim-under-bucket system, while the two exhausts incorporate shims between the rocker arms and keepers on the valve stems.

Share this post


Link to post
Share on other sites

Hey Throttlehockey,

Thanks for the Honda quote. I do feel a little better now about my chances of avoiding a valve job in the near future.

Dick

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

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

Reply with:

Sign in to follow this  

×