Camshaft question

Hi everyone.

Decided to take care of annual stuff (valve clearance checking etc.)

found that the left exhaust valve was a little tight. No problem, a new shim will take care of that. However i found that the surfacefinish close to the cam lobes was worn on the intake cam. Worse on the right, a little bit better in the middle and no wearing at all on the left one. I took the intake camshaft to my Yamaha and showed it to the mechanic. Got a second opinion and I'm going to use it this season. The question is:

Is the cam solid hardened or just surface hardened?

And what could have caused this problem?

I could count several factors that might be responsible but none of them applies here (oil starvation, massive overheating etc.) Could it be problem with the hardening process.


Is it just normal wear? I have never seen a WR450 camshaft before so I don't know how they're supposed to look when they wear. (Which I suppose they do).

Any suggestions or comments will be appreciated.


Hi everyone...even tough I didn't receive any comments concerning this subject I went ahead and put the things together.

Some notes to share with the rest of you (hope it might help anyone doing the same procedure):

1. Before removing the timing chain count the links, mark the sprocket or simply take a picture with a digital camera. It quickly gets very confusing especially after the cam chain tensioner is removed.

2. On the flywheel there should be a line to indicate when the piston is TDC according to the manual. Well, there is actually 3 lines. I guessed that the first line is advanced firing, the second line is the fire position and the last one TDC. Anyway neither one made the punch mark on the camshaft sprockets line up correctly when I removed the timing cover.

Sometimes theory and reality does not match each other. It was off by a few millimeters.

This got me somewhat confused...but I turned the engine to TDC, aligned the punchmark on the sprockets and attached the timing chain.

3. The timing chain will only go over the sprockets when they are in a certain position. Hard to explain but pay attention to how you get the camshafts out because you have to reverse the procedure to get them in. there is not much free play in the timing chain even with the tensioner removed.

Absolutly no violence will be necessary to fit the camshafts if done correctly.

3. Watch out for the little halfmoon shaped clips both when removing the camshaft caps and when putting them back. This could not be stressed enough: put a rag or something to cover the timing chain hole. To drop something here was one of my worst fears.

4.When you have the camshafts dismounted take the time to measure them with a micrometer. Only takes a few minutes and it is always good to know that they are in spec.

5. Do torque the camshaftcaps with a torquewrench. Upon looking on the design of the bearing you soon realize that to much pressure here will cause the camshaft to grind the material from the top quite quickly. No hardened removable bearing shells here....the camshaft caps are replaceable for a "small" fee, the top is not. It also shows how important it is to have oilpressure to the top, something that should be checked by loosening the bolt on the right hand side of the top while the engine is running. now that I come to think of it, why not fit an oilpressure contact here? Just a lamp by the handle bar to see if the pressure is OK....have read here about people who have had their enginges spilled the oil while riding and of course not knowing of it.

I did somemore modification on the bike while I was working with it.

Mounted a frontbrake pressureswitch to activate the brakelight.

Replaced my brakefluid and vented my brakes

Replaced the coolant and the oil + filter

Bought a new seat (SDG) and trimmed it down to fit my short legs.

This is what I love about this forum, there is always help to get from here.

Even tough I didn't get any help on the camshaft question I found subjects regarding everything else here which helped me out a lot when I ran into problems or wonderings so if any of this helps another fellow rider I'll be glad.


Awsome information...

With 400+ miles on mine I'm prepping to go in and check valves for the first time.


I just checked (and reshimmed - all 5 valves were just tighter than the tight end of the tolerance range) my new motor. I am glad that I used a Sharpy pen to reference mark the chain and cams. If you don't, you won't know if you got the chain /cam timing right until you hand rotate the engine and recheck the marks (yes its the third flywheel mark - the one by itself). Then if its off, disassemble and reinstall the cams - avoid the extra work! By the way, the Sharpy marks disappeared the first time the chain rotated through the oil, so make sure you are confident the marks lined up right before you rotate the crankshaft.

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