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This is one of the best articles I've read explaining what a "valve job" really is. He also covers why the valves are replacement only.
Valve Jobs Done Right
Valve Jobs Done Right
Valves and valve jobs
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Weeelllll, when he said, "You have to understand one thing, no one who goes to the trouble of pressure or vacuum (my preference) testing their valve seat sealing bothers to use Neway cutters in the process of getting there. Not more than once, anyway. Believe it." -- No, I don't believe it!
His statement about the dead pilot's taper guaranteeing eccentricity is hooey also. The taper is so very gradual that the pilot will be on center with the guide. If not, he used the wrong size pilot, or his valve guides were egg shaped and should have been replaced.
I have three motorcycles whose seats were cut with Neway cutters, and we did a leakdown test on each one, using a leakdown plate similar to the one in his picture. They all tested at 98 to 100%. That is even before any springs were installed. All three bikes run great, with no problems. I would like to read his reasoning for preferring to use a vacuum test. I believe the pressurized leakdown simulates what will happen later in the real life cylinder.
My Honda cylinder did not get this treatment because it passed an "acetone test". Also, I took to heart your discussion back then about not grinding the Honda valve faces. On my BMW, the Clymer manual discourages that for the same reason -- removal of the thin Stellite coating. However, the BMW factory manual says to do it and even includes a picture of the valve face grinder in use. Go figure!
He may be right about the shim and bucket engines. I never plan to own one of those. :-D
Ray
His statement about the dead pilot's taper guaranteeing eccentricity is hooey also. The taper is so very gradual that the pilot will be on center with the guide. If not, he used the wrong size pilot, or his valve guides were egg shaped and should have been replaced.
I have three motorcycles whose seats were cut with Neway cutters, and we did a leakdown test on each one, using a leakdown plate similar to the one in his picture. They all tested at 98 to 100%. That is even before any springs were installed. All three bikes run great, with no problems. I would like to read his reasoning for preferring to use a vacuum test. I believe the pressurized leakdown simulates what will happen later in the real life cylinder.
My Honda cylinder did not get this treatment because it passed an "acetone test". Also, I took to heart your discussion back then about not grinding the Honda valve faces. On my BMW, the Clymer manual discourages that for the same reason -- removal of the thin Stellite coating. However, the BMW factory manual says to do it and even includes a picture of the valve face grinder in use. Go figure!
He may be right about the shim and bucket engines. I never plan to own one of those. :-D
Ray
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I have some general disagreements with the article based on real life experience like you. By in large it's well written and understandable for the lay person who hasn't dealt with this stuff on a professional level.
I remember having an argument with my apprenticeship instructor when he was showing the class how to do a single angle valve job. I had been doing 3 angles for a couple of years at the time, 1971.
I remember having an argument with my apprenticeship instructor when he was showing the class how to do a single angle valve job. I had been doing 3 angles for a couple of years at the time, 1971.
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I think the tightest live pilot you can use the better, and if it's solid carbide that won't flex, all the better. I think the guide clearance and straightness is paramount. Lapping in old reground valves in worn guides won't help the valve seat and the spring will drag it closed and you'll shortly be worse than before. You may not burn oil but performance will be soggy. I liked his cylinder bore article too. My 450 is "soggy" but I think the older bikes probably wear out faster, and if you want it faster, get a newer bigger bike. Most people don't want to rebuild something every 20,000 miles. I was riding with my daughter the other day about 65mph, gave it the gas and "bleaaah". I guess my worn 750 would've gave me the acceleration I was looking for but then I'd probably want a 900.
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Here's a good one explaining why the newer serdi style machines are so adored.
Head Rebuilding -
Head Rebuilding -
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