How long will valves last after shimming?

I finally had to shim my right in-take valve. After studying the posts on the topic, I am wondering how long the stock valve is likely to last now that it has moved.

My bike is a 2004. I am a recreational rider, so I don't run at really high rpm all that much, and I don't get a ton of hours on my bike (unfortunately). I would guess that I have just over 100 hours by now.

I had been checking the valves about once a year, and they hadn't moved as of my last check in 2006. In 2007 I had a dealer check them and I thought they changed the shims, but they didn't. Maybe they didn't even check it???

But on my last trip the bike became extremely difficult to start, so I checked the valves when I got home. The right in-take was down to 0 clearance. I replaced the 192 shim with a 170 shim and I am now back at spec.

Some of the TT posts indicate that once the valve starts to wear, it will require re-shimming more frequently or require new valves soon. So, based on my riding profile, how much life should I expect from my valves and current shim setting? I bought the shim kit, so I can change shims as needed, but if it requires changing frequently I would just as soon replace the valves. Or am I likely to get another 4 years before needing another change?

My current plan is to run the engine with the 170 shim until it needs to be changed and then just replace the valves. Is that a reasonable plan? Or should I continue to replace shims? Or should I replace the valves now to prevent damage to the head?

It seems that the general preference for replacement is to move to stainless steel valves. I assume I would replace all four valves as well as the springs. True? Should I also replace the cam? Do I need to replace the head?

Thanks for any advice.

Order now and you might get another day out of riding.

Chances are, it will only last for a few rides--I have an 04 also, and have seen this same situation--I think I got 2 or 3 races after the shimming, and then the next time I hauled it way off to do an event I barely was able to get it started. So, based on my experience, I would agree that you should go ahead to order-up some new valves and associated parts. I recommend going to stainless steel for the intakes and use stock Honda parts for the exhaust. You will need new springs that are appropriate for the valves, and you'll need the head re-conditioned or a new head. You do not need a new cam. If you have the head re-conditioned, that should include installing new valve guides as well as having the seats re-cut. If you replace the head, investigate which one to use--I used an 06X head because the seats were changed to improve valve life, but some have since suggested that the harder seats in the 04 & 05 models are actually a better match for stainless valves. Whichever valves you use, I have found that leaded fuel lengthens their lifespan.

So is it even worth buying the shims and going through the trouble. I have an 07 with about 10 hours on it. Planning on checking valves this winter. Thinking about just sending the head to Agent for SS valves and a rework if it is very far out.

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