Lapping the head to repair a head gasket - Ex-500.com - The home of the Kawasaki EX500 / Ninja 500R
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post #1 of 147 (permalink) Old 1-23-2007, 1:03 PM Thread Starter
fog
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Lapping the head to repair a head gasket

Head Gasket repair
Lapping the head
By FOG

A common failure of the EX engine is, a blown head gasket. The usual cause of this besides the obvious low water or frozen coolant reasons is, warpage of the mating surface between the head and the cylinders. The string of events leading to overheating is:
High pressure gas leaks from the combustion chamber into the coolant system, thereby over pressurizing it and blowing coolant overboard, then the coolant shortage causes overheating which causes even greater warp age, add on infanatum...

As well as the above, any engine that has had the head removed for any reason need to be re lapped. This engine is a very flexible unit because of the cam chain gallery down the middle. The only thing holding the two cylinders together is the very thin wall of the front and back sides of the chain gallery. 1/8” if you’re lucky. This means that the engine works like two single cylinder engines running from a single crank held together by scotch tape. As long as they remain together they are usually fine, but once disassembled they need to be re flattened

The repair:
Unfortunately it is not a simple as replacing the head gasket. Because the “gasket” is not compressible, it is not able to absorb even slight distortion or warp age that may not even be detectable with the usual straight edge type of inspection. The up side of this is that you can re use the gasket.

Tools needed:
A lapping plate; usually a steel flat plate or a pain of flat plate glass. I’ve used my table saw table successfully (the cast iron type)
Lapping compound: Valve lapping compound available at a Auto parts store
The means to wash the parts clean after lapping. A bucket of Kerosene is fine.

The Idea is to use the abrasive to grind down the high spots of the head and the cylinders till they are perfectly flat. See the pictures.

The process move the part over the surface of the Lapp in a figure 8 motion
Clean and inspect your progress often. Shown is a partially cleaned surface

Here are the completed two parts.


You are now ready for reassembly. Clean the old head gasket with lacquer thinner and Scotch brute or steel wool. Then repaint it with 1 coat of spray enamel on both sides (1 coat)
You ought to re- fresh your valve seats now too.
After assembly increase the Head Bolt torque to 40 lbs. ft.

Now’s a good time to degree you cams.

Pi1 shows a freshly lapped set
P 2 shows the process and the lapp plate
p3 showa a partiallycleaned up head with the dark spots still holes in the surface

PS. I have found a good source for a suitable lapping plate is a Granite shop. One that actually cuts the stone for counter tops. They have a pile of sink drops out back that they will give you for free. (usually). these are good 1 time tools

Good luck
FOG


[attachment deleted by admin]
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File Type: jpg Head lapping 001.jpg (834.2 KB, 910 views)
File Type: jpg motor 035.jpg (804.5 KB, 925 views)
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post #2 of 147 (permalink) Old 10-29-2008, 7:06 PM
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Re: Lapping the head to repair a head gasket

exactly how effective is this technique for lapping the head and barrells?

can it go wrong?

Dale
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post #3 of 147 (permalink) Old 10-29-2008, 7:15 PM Thread Starter
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Re: Lapping the head to repair a head gasket

Only if you do it wrong.

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post #4 of 147 (permalink) Old 11-20-2008, 1:06 PM
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Re: Lapping the head to repair a head gasket

I have heard some people use a piece of granite tile, DO NOT DO THIS, I have been a granite installer for many years (father has a tile co. brother has a tile co. uncle has a tile co. you get the picture) and never have I seen a piece of granite tile that is perfectly flat, ever..

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post #5 of 147 (permalink) Old 11-20-2008, 1:35 PM Thread Starter
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Re: Lapping the head to repair a head gasket

Hey Tile person, Question. Years ago I had Granite kitchen counters installed and I had a time finding a co. that had the equipment to do this. Apparently a large CNC mill using diamond tools. Down here in Mountain Home, AR there are a least 5 companies in this business.Has the cost of this equipment suddenly dropped?

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post #6 of 147 (permalink) Old 11-20-2008, 2:22 PM
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Re: Lapping the head to repair a head gasket

no, why do you ask?

yesterday dont mean shit! tomorrow is the day you have to face!<br />R.I.P BAM BAM, Conrad and Soladad.
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post #7 of 147 (permalink) Old 11-20-2008, 5:09 PM Thread Starter
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Re: Lapping the head to repair a head gasket

Quote:
Originally Posted by solar-ex
no, why do you ask?
Like I said 5 companies in a little town of 12.000 seems to be a bit much. I would think the sales in this area would not support so many 100K machines.

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post #8 of 147 (permalink) Old 11-20-2008, 5:30 PM
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Re: Lapping the head to repair a head gasket

I agree, but the thing is they dont use the mechine themselfs, they order the granite in "raw" slabs. They are usually 8-12 feet across, polished on one side and have no definite shape.

they then cut it to fit the customers needs, they use a profile wheel to shape the edges and then polish them.

yesterday dont mean shit! tomorrow is the day you have to face!<br />R.I.P BAM BAM, Conrad and Soladad.
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post #9 of 147 (permalink) Old 11-20-2008, 9:58 PM
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Re: Lapping the head to repair a head gasket

Quote:
Originally Posted by solar-ex
I have heard some people use a piece of granite tile, DO NOT DO THIS, I have been a granite installer for many years (father has a tile co. brother has a tile co. uncle has a tile co. you get the picture) and never have I seen a piece of granite tile that is perfectly flat, ever..
I did this a couple of months ago. So far, no problems, but I did have to sort through some tiles with my straight-edge until I found a good candidate.
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post #10 of 147 (permalink) Old 12-3-2008, 10:38 PM
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Re: Lapping the head to repair a head gasket

I've been racing Honda's for 7 yrs, 2 and 4 cylinder.Lapping the head seems to be a good idea,,make it true.I had a problem with a motor, but it was the cylinder liner not being flush with the top of the cylinder casting, and it disintegrated a head gasket..slowly!(it was lapped by a machine shop)I was at Shannonville and watched a racer spray paint the head gasket on his fzr 600. I have built several air cooled twins and have never trued the casting(um read above) and they work fine!,,Are head castings on ex 500's prone to warp?? remember I'm new to this gig,,are the head gaskets expensive?? please your comments,,,thxs JD
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post #11 of 147 (permalink) Old 12-4-2008, 9:14 AM Thread Starter
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Re: Lapping the head to repair a head gasket

Read the article at the top .

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post #12 of 147 (permalink) Old 3-31-2009, 1:20 PM
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Re: Lapping the head to repair a head gasket

I am way impressed with this. How do you know all of this?

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post #13 of 147 (permalink) Old 3-31-2009, 1:41 PM Thread Starter
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Re: Lapping the head to repair a head gasket

Quote:
Originally Posted by richardlwebbjr
I am way impressed with this. How do you know all of this?
I raced this machine for 12 years and managed a team of three riders and bikes. This overheating problem was so chronic with these bikes I set out to find the reason. Being an engineer and owning a very capable machine shop I was able to see the warpage that occurs on this engine that would otherwise be considered OK by a typical mechanic. I determined that creating a good flat surface match was the key and have repaired maybe 50 engines in said manner.
Finally I'm a 70 year old genius.

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post #14 of 147 (permalink) Old 4-5-2009, 2:29 PM
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Re: Lapping the head to repair a head gasket

so, for an average mechanic, how long do you think this process would take...... Start to Finish....

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post #15 of 147 (permalink) Old 4-5-2009, 5:24 PM Thread Starter
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Re: Lapping the head to repair a head gasket

For me or you?

Me 1 hour.
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post #16 of 147 (permalink) Old 4-5-2009, 8:33 PM
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Re: Lapping the head to repair a head gasket

Wow, not fair. I couldn't even get the cam chain off LOL. So, getting a Haynes manual tomorrow and trying again. Spring Break this week. All I gotta do is go to work and then I can work on the bike. I had it running so good today and was really bummed when all that coolant spewed out.....

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post #17 of 147 (permalink) Old 3-30-2010, 11:51 AM
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Re: Lapping the head to repair a head gasket

If I am using an abrasive lapping compound on a glass or tile lapping plate would it not wear away the much softer lapping plate before the much harder metal surface that I am trying to smooth and in the process make it impossible to even out any irregularity?


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post #18 of 147 (permalink) Old 3-30-2010, 12:42 PM Thread Starter
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Re: Lapping the head to repair a head gasket

Yes and that's OK be sure to cover the entire surface of your plate with the strokeing action to keep the wear even. change the orientation of the plate to the head often.

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post #19 of 147 (permalink) Old 3-30-2010, 2:34 PM
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Re: Lapping the head to repair a head gasket

I was just wondering FOG, cause this link popped up on the forum for me yesterday; could this stuff be used to fix the head on our bikes?
http://www.steelseal.com/

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post #20 of 147 (permalink) Old 3-30-2010, 3:04 PM Thread Starter
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Re: Lapping the head to repair a head gasket

I don't know, Sounds like Snake Oil to me ,but maybe. Depends on how much combustion pressure it will withstand. Somebody will have to try it.

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post #21 of 147 (permalink) Old 3-30-2010, 3:23 PM
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Re: Lapping the head to repair a head gasket

Quote:
Originally Posted by FOG
I don't know, Sounds like Snake Oil to me ,but maybe. Depends on how much combustion pressure it will withstand. Somebody will have to try it.

FOG
well its expensive stuff so it better work! if my head gassket ever needs a fixin ill be sure to try that stuff and review it.

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post #22 of 147 (permalink) Old 3-31-2010, 12:56 AM
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Re: Lapping the head to repair a head gasket

A product that you pour in that claims to plug up a head gasket? I think this part of a testimonial that tells you what the product is useful for:

"Several mechanics tried to repair the leak with all kinds of stuff. This engine must have been overheated 20 times. Now it runs very smooth and powerful. I can now sell it and make a profit. Thank you Steel Seal. "

I'm extremely skeptical. But if the product actually does this for any temporary amount of time, that can be useful for people that get hit with a sudden head gasket failure.

And there should be some sort of actual visual confirmation of its properties via some kind of example setup for the video.
post #23 of 147 (permalink) Old 12-29-2010, 1:24 AM
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Re: Lapping the head to repair a head gasket

I feel a bit silly asking this, but does anyone have any suggestions where to get a cheap plate to do the lapping with?


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post #24 of 147 (permalink) Old 12-29-2010, 10:12 AM Thread Starter
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Re: Lapping the head to repair a head gasket

Some table saws have a cast iron table, I used mine succesfully before I aquire a proper tool.

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post #25 of 147 (permalink) Old 12-29-2010, 1:21 PM
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Re: Lapping the head to repair a head gasket

Quote:
Originally Posted by FOG
Quote:
Originally Posted by richardlwebbjr
I am way impressed with this. How do you know all of this?
Finally I'm a 70 year old genius.

FOG
I was wondering about that and this explains ALOT about your knowledge and experience.

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