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2008 KX 450 topend rebuild at 350 hours

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Bought my bike new in 2008 , have done all the regular maintenance like oil and filter changes every 10 hours , air filter cleaned every ride , shims I checked about every 40 hours .

Inlets started needing shimming regularly from about 300 hrs and i knew i was riding on borrowed time .

Decided to change the inlet valves and at the same time do the piston as the motor had not been opened in 350 hours .

Piston has slight wear on the centre of the skirts , barrel still excellent condition with no ridges or scratches , piston pin had a little wear . All parts still in spec as per manual .

Left inlet valve was very worn , right inlet was better than ive seen on bikes with less hours .

Replaced the inlet valves with OEM valves and replaced piston kit with Wiseco standard compression .

450 was a pleasure to strip as everything is easy to get to , and parts are not small like on the 250's ive worked on .

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Bought my bike new in 2008 , have done all the regular maintenance like oil and filter changes every 10 hours , air filter cleaned every ride , shims I checked about every 40 hours .

Inlets started needing shimming regularly from about 300 hrs and i knew i was riding on borrowed time .

Decided to change the inlet valves and at the same time do the piston as the motor had not been opened in 350 hours .

Piston has slight wear on the centre of the skirts , barrel still excellent condition with no ridges or scratches , piston pin had a little wear . All parts still in spec as per manual .

Left inlet valve was very worn , right inlet was better than ive seen on bikes with less hours .

Replaced the inlet valves with OEM valves and replaced piston kit with Wiseco standard compression .

450 was a pleasure to strip as everything is easy to get to , and parts are not small like on the 250's ive worked on .

Wow, that's great that you got that many hrs. I hope I'm as lucky. I am also a nut with the maint. I hope it pays off.

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Nice. What type of oil do you use in it? Any thoughts on your bottom end wear? I know your exhaust valves hadn't pulled up, but were the seats pitted and/or bases of the stems coked up?

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Was not much carbon around the exhaust valves , lot less than I expected . Could not feel any wear on the conrod .

Using Motul 5100 semi synthetic oil .

I never take the bike near the limiter , most of my riding is done on trails where I use bottom to midrange power .

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Good job, I have an inlet valve on my 06 that tightened right up. I shimmed it, but was nervous about it's future. (Was thinking the hard coat was wearing) So I check my valves every ride. But it hasn't budged in nearly 30 hours. But it's hard to shake that voice in the back of your head. We don't want a valve to dance with a piston! heh. I'm currently working on my carburetor with some excellent help from the above poster krannie, and depending on my inlet valve/season. Will do the valves and check the top end this winter!

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Thanks Shawn250. You got a good motor under light loads. If the crank is balanced nicely, which perhaps depends on some luck with stock engines, then I guess the loads on the bottom end are less.

My 06 engine feels like it has very little vibration compared to some (or all) other 450Fs I've ridden, and after 295 hrs I assume it means something.

Themitch, once the valves pull up, they are on borrowed time and on the way out. I think you'll find the engine is hard to start before anything worse happens. The EOM Kawi valves and seats are great for strength and wear, but with enough dust and/or hours they'll wear eventually. You get a groove on the seal surface of a worn valve.

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You don't need to worry about a valve dancing with the piston just because you need to shim it once or twice. A totally different problem needs to occur for that to happen.

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Numroe, I got about 20hours on the bike since I shimmed that intake. Hasn't budged yet. When it does, i'll start to think about new valves

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Valves moving on the first initial hours is completely normal,in fact most valves do.With ti valves they might move on the first hours,then keep the tolerance for a long time (100-300) until they start moving.Thats when you need to replace the valves.

Also,it is absolutely necessary to recut the seats with new valves or your throwing away your money.

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