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Engine valves may be off, even if no signs are showing!

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I just got done doing the first valve clearance check AND valve shim adjustment. I let it go 1600 miles between being checked (2003 wr250f). This is because all the info on this site indicated that there are some sure signs when your valves are too tight or too loose.

1) loss of power output

2)difficulty starting

Well, my bike has never had issues starting. In the cold it would kickstart in about 3-4 kicks, cold engine. Electric start took a couple tries but never significantly problematic.

So, I assumed that since I had none of those (2) issues above, that my valves must be fine. I decided to ball up and teach myself how to check, and if needed, reshim my engine valves. When I first measured my clearances I freaked out. ALL five valves were out of spec.

Manual calls for intake valves to be .1 - .15mm

Manual calls for exhaust valves to be .17 - .22mm

MY 3 intake valves were all around .07mm

My 2 exhaust valves were both around .14mm

Drastically out of spec! So, after a lot of cussing, and aching back, and slipping on spilt oil on my garage floor, I managed to reshim all 5 valves. After reassembly all 5 valves are now in spec. With a little 'cushin' room. Well, I decided to start it up and let it idle to make sure all was well. The bike came to life. It now starts on 1, usually 2 kicks, and it just SOUNDS healthier. When I rev it, it responds faster and sounds more uniform.

I realized that valves do indeed need to be checked for clearance, even if you 'seem' to have no issues. Maybe I didn't notice my bike's lack of power and lack of revving ability, because I was used to it. Lesson for everyone to learn: Check your damn valves. $27 is all it cost me, and I know they'll be good for another year the way I ride this thing....

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you'll only have starting and power problems when the valve tolerances get's to 0 and the cam holds the valve off the seat during the compression and power stroke, the reason for valve tolerance is to give the cam lobe some "ramp" allowing more aggressive cams to be run with less risk of damaging the shim buckets, you'll actually make slightly more power with tighter valve spec's due to the valve's opening slightly longer with slightly more lift, also the alloy head's on our bikes expand more then the titainium or steel valve's do, so the clearance get's larger as the engine warm's up.

the other thing is, that your bike has titainium valves, which have a hard coating on them to prevent wearing, once the coating wear's off the seating area'and get's down to the bare titainium, they will wear very quickly, the coating is only .02-.03mm thick, so i suggest you keep checking your valve's, it's also possible that a previous owner purposely shimmed them tight for reason's mentioned above.

Edited by Ttoks

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True. But having too tight a clearance does not allow for proper expansion of the valve when it heats up. I do intend to ckeck my valves more often. Probably after another 20 hours of riding. I agree that technically tighter = more open valve = more HP, but i prefer to stay in spec now

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the better you get to know your bike, the more likely you are to notice the gradual loss of performance associated to valve wear.

I've learned a lot of things the hard way...but I tend to pick up a few things as I go along...then I buy a new bike :bonk:

Edited by Slackkinhard

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More than 1 or 2 kicks IS hard starting for me! :bonk:

I hear a lot of guys say that after shimming twice, it is time to chuck the valves. With fresh valves, after how many hours should the valves be checked for the first time?

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