When to trade up?

[marks]

I have a steel frame 06 wr450 which I brought as new old stock just over 2 years ago. Its got about 160 hours on it now (original piston) and I have discovered a couple of inlet valves are a couple of thou under minimum spec (been checked a couple of times previously and were always ok).

Do I
a/ re-shim them and assume its all good and throw a new piston in at some future time (I have a JE piston kit sitting here).
b/ pull the head off to see why the valves are tight and throw the new piston in and expect the bike to last another 150 or so hours without any 'big bangs'
c/ decide its only going to cost more and more as it gets older so I tart it up and sell it and buy a low hour minter.

is 300 hrs realistic out of the bottom end/gearbox? (it gets regularly properly serviced)

bike is used for trail riding by a slow old fart.

thanks


Mark

[kezzafish]

I recon she's had a good run and don't tempt fate... replace 2 inlets and the piston

[camchain]

I had to replace inlet valves on last bike (KLX). As soon as I had to start adjusting them, I had to shim twice again inside 10 hours. It was clear that once through hardening they were shot. Yours could well be a different story though.

Your bike sounds well maintained and not hammered so my guess your bottom end could be fine for least another 150hrs maybe even more. Others will know more than me on this. I heard the Powers had a CRF that had 400 odd hours on same bottom end.

[CRF119]

Once valves need to be reshimed it all down hill from there the material will just start to strech. Replace all 5 and do piston, no point in doing 2 just toi find out 10 hours later the other ones are stuffed and you need new gaskets again. Then you are good for another 150 hours +.

Bottom end will depend how you ride the bike keep an eye on your oil filters even rinse them in petrol after use and inspect for any metal parts that will give a indiaction if bottom end is going. Ive herd of bikes lasting 400 hours hours on bottom end. Just keep a close eye on everything.

[camchain]

Here's a couple of pics of my valves after approx 150hrs.

Exhausts had no visible wear but I replaced them anyway. Wouldn't do exhausts again (on this model) under similar circumstances, was a waste of money. Inlets always wear a lot faster. I went over the top and did guides/seals as well and it all adds up $$$.

See the inlet valve was very worn at seat contact area. It's scalloped out, but hard to spot from pic that it had quite a sharp edge and was pretty thin. Much more wear than this, and I could imagine edge starting to break off (Don't know if this actually ever happens though!).

Can't remember if yours are all titanium but hardening will probably have different wear characteristics. Maybe hard layer doesn't just stop suddenly? I'd be tempted shim them right now and see how they go out of curiosity, then you'll know exactly how fast they're wearing. Useful knowledge for future.

You'll probably already know this, but thing you have to watch with titanium, is valves are made with two pieces and stems are welded on. They can break with fatigue so definitely check what normal service life is.

[marks]

thanks for the responses guys

I'll get the valves reshimmed and check them again in 10 hours and if they haven't moved again in another 10 hours. If they move I'll get the top end done straight away and if not I'll leave the piston alone until the 200hr mark.

I'll be strong resist the temptation to use this issue as justification for buying that nice little 525 6 days I've been drooling over......

[camchain]

I'd still keep open ear for more qualified info though. Plenty of Yamaharians on here. KLX300 not the best comparision to WR 4 fiddy but anyway, my piston was near mint so it went back in and just did rings.

Heh, when first read your thread title 'when to trade up?' my first thought was - whenever you can afford it. Trading UP? Mmmm Orange...