Author Topic: Lapping compound?  (Read 5169 times)

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Offline 70CB750

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Re: Lapping compound?
« Reply #1 on: November 19, 2013, 03:59:36 AM »
I'm no expert and I'm sure they will chime in but I think of it like sandpaper there are different grits depending on how much it needs done. if you do it just after a valve job use the fine. You can get it at almost any auto parts store cheaper without shipping.

Offline Ace

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Re: Lapping compound?
« Reply #2 on: November 19, 2013, 04:10:13 AM »
I've just lapped some valves in. Needed coarse grit to get some of the pitting out then finish off with fine grit.  Came in a double ended tube, coarse one end the other fine.  Valves lapped in fine and no leaks afterwards when tested with 5w oil. Third head I've done like this.
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Offline skidooextreme

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Re: Lapping compound?
« Reply #3 on: November 19, 2013, 05:16:04 AM »
Why would you test leaks with oil?  Use diesel or gas with the head upside down.  Air is tricky and will blow through the slightest small hole.  Liquid will show you problem areas faster and much more accurate

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Offline Xnavylfr

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Re: Lapping compound?
« Reply #4 on: November 19, 2013, 05:28:55 AM »
SKID is correct!!  Use some thin liquid to check for valve leaks. The molecules in the oil bind together and if it is a small leak oil may not seep pass!!
Lapping compound usually is in 2 grits / coarse and fine. Be sure to use the hand lap method not a drill attached to the tappet end.


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Offline 70CB750

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Re: Lapping compound?
« Reply #5 on: November 19, 2013, 05:50:02 AM »
Hondaman talks about 5 weight oil in his book.  I used rubbing alcohol to leak test.
Prokop
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Offline skidooextreme

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Re: Lapping compound?
« Reply #6 on: November 19, 2013, 10:16:30 AM »
Does he use this method with the engine altogether ?  I will agree if thats the case

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Offline dave500

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Re: Lapping compound?
« Reply #7 on: November 19, 2013, 11:27:25 AM »
i use a hose chucked into reversible variable drill on the valve stem end,run it both directions,just dont spin the #$%* out of it.

Offline Vinhead1957

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Re: Lapping compound?
« Reply #8 on: November 19, 2013, 01:06:58 PM »
Go to NAPA and pick up a tube!  Use a marker pen and make lines across the valve surface. While you are at Napa pick up a lapping tool. A double ended suction cup device.  Use the tool by hand.  By HAND only. Lap the valve until the mating surface connects all the lines. It is a fine process. Only to verify the seat and valve have a good mating surface. Ideally the line it makes is as wide as the seat surface.

Offline LesterPiglet

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Re: Lapping compound?
« Reply #9 on: November 19, 2013, 02:44:58 PM »
The tool.


The paste.



I do it all by hand, I don't have a significant other.   :P
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Offline 70CB750

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Re: Lapping compound?
« Reply #10 on: November 22, 2013, 09:31:29 AM »
Could we talk some numbers here.  Like Coarse compound to use is 80 and Fine compound for lapping valves is 200 grit?

Feeling in the dark here, what #s do you use?
Prokop
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Offline flybox1

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Re: Lapping compound?
« Reply #11 on: November 22, 2013, 09:35:10 AM »
The Permatex tubes I purchased, had no numbers. 
It was either fine or coarse.   I have yet to use.
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Offline iron_worker

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Re: Lapping compound?
« Reply #12 on: November 22, 2013, 10:06:18 AM »
The set I bought from Canadian tire has 120 and 280.

http://www.canadiantire.ca/en/pdp/powerbuilt-valve-lapping-compound-0253201p.html#.Uo-c7NIw3G4

Whether it's any good or not ... I don't know. lol

IW

Offline 70CB750

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Re: Lapping compound?
« Reply #13 on: November 22, 2013, 10:13:52 AM »
Thanks, I found some Jeg's compound on ebay I will get when I finally push my blasted jeep through inspection; that's like never ending story.
Prokop
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I love it when parts come together.

Dorothy - my CB750
CB750K3F - The Red
Sidecar


CB900C

2006 KLR650