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Discussion Starter · #1 ·
That is the question.
Whether 'tis Nobler in the mind to suffer
The Slings and Arrows of outrageous Carbon Buildup,
Or to take Lapping Compound against a Sea of troubles,
And by opposing end them
To die, to sleep No more; and by a sleep, to say we end
The Heart-ache, and the thousand dollar repairs
That a leaky valve is heir to? 'Tis a consummation
Devoutly to be wished. To die to sleep,
To sleep, perchance to Dream; Aye, there's the rub.

I know grinding Goldwing valves is a no-no, but what about lapping? I've read to leak test the valves by pouring brake cleaner in the well of the head and look for it to leak past the closed valves. Is a failed leak test the only time lapping is suggested or can I lap at any convenient time like now, when I'm replacing head gaskets?
 

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If you have the heads off, you may as well check the seat seal and replace the oil seals. But maybe I wouldn't bother actually lapping the valves unless it does fail. Which I'm pretty sure a used head will do... At least look at them, maybe clean off the gunk and retry the seal test. A lap job may not do it and you'll be going to the "Midas Well" for new valves because you "might as well".
 

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When a valve is ground the part that contacts the seat is actually a sharp point if it is done right.This to cut the carbon and prevent buildup in that area. If you lap the valves then you get rid of the contact point and have basically two flat spots contacting each other.Good seal initially ,but not so good after a while.Lapping is for lawnmower engines IMHO.
 

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Valves seal via an interference fit, 45 degrees on the seat and 44 on the valve face. Compression and leak down tests should already have been done prior to tear down.

Liguid leaking tests are not an acceptable method for checking fit.

This is what you need to check valve contact area.

[ame]http://www.amazon.com/Permatex-80038-Prussian-Blue-Tube/dp/B000HBM86Q[/ame]
 

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In the automotive world, when doing head work like this, a machine shop typically will not mess with it as long as it passes the testing criteria for sealing up. Valve jobs are only done when one or more valves are damaged for whatever reason. So, in this particular case, I dont see the benefit you will gain by lapping the valves. Unless the seats are somewhat beat up, or the angles on the valve are not perfectly straight, you could leave well enough alone. Either way, it's something I would leave to a machine shop to determine if its necessary and fix. Lapping, IMO, is shade tree-ish and not lasting, quality work.
 

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I was always under the impression that when using new valves and/or seats, lapping was a neccessity to seat the parts together. On an older engine, it was also neccessary if there's any kind of damage. I thought you just throw on some machinest blue and spin the valve around and the shinny bit tells ya what your contact area looks like.

I don't see how it's so evil? :? Seems to me like it's just more thorough :?

I could be wrong though...........
 
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