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Old 12-10-2012, 05:00 PM   #7
Tosh Togo OP
Beastly Adventurer
 
Joined: Nov 2010
Oddometer: 1,594
Quote:
Originally Posted by BOETJE View Post
Go and sit somewhere quiet and think very carefully about what you just wrote...
I did, and I'm still right, while you are apparently confused.

Quote:
Originally Posted by pommie john View Post
What he wrote makes sense to me. If you mill the head, the cam chain tensioner will take up the slack at the back, pulling the sprocket backwards, retarding the cam timing... won't it? Am I missing something?
That's the gist of it.

Quote:
Originally Posted by BOETJE View Post
Yes you do .
If the timing marks line up , like he said, then it doesn't matter how much is milled of the head. Thing is that if you mill a lot off, you might have to slot the cam sprockets in order to make them line up.
If, if, if.... there are a lot of assembly tolerances in the cam-driving system: the crank sprocket, the cam sprockets, and the mounting holes to mate each cam to its' respective sprocket. cam. There's also the assembled height of the cams' axis versus the crank sprocket.

This potential stack-up of tolerances is the biggest single reason that otherwise identical stock bikes will often have very different personalities... two degrees will make a measurable change in the torque curve.

The Japanese factories do a good job of it, but there's still inherent variation in the results: there are many little opportunities for the valve timing to end up to not be what you think it is, and the only way to be certain is to degree in each cam. Your presumption that the standard timing marks is optimal is not shared by very many other engine builders, so please stop with your enthusiastic-but-misguided ways to "help" me.

I need actual timing numbers, not someone's opinion that the lazy way of engine building is OK.

You do your cams your way, and I'll do mine the way I was taught.
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