When Should I Think Of Relpacing The Valves ????

I have been getting all the parts together for a complete rebuild of all the major componets. I have a 03 WR 450 that has been plated since it was new. I have about a million miles on it with no problems. I was racine both my inlaws on ther KTM 525's on the road and strung mine out long time. After that is had started useing oil some and will not start good anymore. I am guessing that the piston was trying to get sidways in there and might have took off some cylinder plateing so I have low compression and oil blow by. I don't know anybody that has had any issues with the valves in the bike or the quad. Do they wear out?

Thanks

Todd

I just went through the head on my 03. It had well over 10,000 miles on it. The valve clearance on these bikes is pretty stable and rarely requires reshimming. If you find it starts moving on you and you have to reshim more than once or twice in a short period then it's time. Given the mileage on your bike I'd plan on new valves, guides and seals. You'll probably need a new cylinder, piston and rings as well. Take a look at the rod and crank while your at it. It's cheaper to do it before it grenades!

I doubt your piston took off some cylinder plating. It's nikasil. That stuff is tough. Your piston probably rubbed a little and now there's less compression or your valves just aren't in spec.

I have a new piston kit, cylinder and crank on hand along with 25 other pieces. The nickasil will flake off sometimes when wore out or piston damage has got to it. Seen it 30 or 40 time now over the years with mostly the snowmobiles and a few dirt bikes and quads. You are right on not haveing to adjust valve very often. I have done it 3 times orer the years with very little adjustment needed. I did check them this summer, so i will rule out needing a adjustment for now. I am trying to make it till winter befoe I tear into it. Any body else have any info??

Thanks all.

In my case the nikasil was fine but there was a pretty good groove worn at the base of the stroke where the piston changes direction. Sounds like you're on the right track.

I just went through the head on my 03. It had well over 10,000 miles on it. The valve clearance on these bikes is pretty stable and rarely requires reshimming. If you find it starts moving on you and you have to reshim more than once or twice in a short period then it's time. Given the mileage on your bike I'd plan on new valves, guides and seals. You'll probably need a new cylinder, piston and rings as well. Take a look at the rod and crank while your at it. It's cheaper to do it before it grenades!

so then why do they say check the valves every 15 hrs if they rarely need reshimmed

After owning 5 WR4xx's my experience has been that they rarely need shimming. I check mine about two or three times a year. I've only had to reshim a couple of times and then by only .001". In the case of my '03 the valves finally went away and I had to start shimming a couple of thousandths every couple of rides so I knew something was up. I'm a casual rider. I ride hard but I don't race. If you're racing you'd probably want to check them more often.

so then why do they say check the valves every 15 hrs if they rarely need reshimmed
Because one day, eventually, they will need it, and if you still own the bike when that happens, you'll want to know it as soon as possible so you can prevent it from turning into a larger problem.
Because one day, eventually, they will need it, and if you still own the bike when that happens, you'll want to know it as soon as possible so you can prevent it from turning into a larger problem.

alright got ya:thumbsup:

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