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How perfect should Valve timing be?

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Last time I took a look at my valves clearance, I briefly checked the timing chain and noticed that at TDC my valve cams were slightly off set, not much, but they were not the perfect 90 degree match the manual made it look like. Is this normal or could it be from timing chain stretch, or something else? 

How many hours before I should change my timing chain?

it's a 07 YZ250F

 

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Forget my first question. I pulled the valve cover off and rechecked, what I found was that the intake valves were in-fact off by a tooth. They were one tooth too far clockwise, so I corrected it. I've been running it like this for several hours and it ran pretty darn good.

 

Does one tooth off timing make a big difference? I'm hoping it will run better now

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7 hours ago, xtactical said:

Forget my first question. I pulled the valve cover off and rechecked, what I found was that the intake valves were in-fact off by a tooth. They were one tooth too far clockwise, so I corrected it. I've been running it like this for several hours and it ran pretty darn good.

 

Does one tooth off timing make a big difference? I'm hoping it will run better now

I'm not sure it will run when it is one tooth off. Change the cam chain.

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Well again, it actually ran kinda well like this amazingly enough. I fixed it and man does it sound better, start easier and wined up faster.

Heres what blows my mind, the last person to be inside this engine was a motorcycle repair shop, when they rebuilt the top end. This is the reason why I do my own bike mechanics, shop probably paid some teenager minimum wage to put it back together...

Edited by xtactical

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