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Lapping the head to repair a head gasket comments thread

38K views 145 replies 32 participants last post by  jkv357 
#1 ·
exactly how effective is this technique for lapping the head and barrells?

can it go wrong?

Dale
 
#28 ·
Sorry to dig up an old thread, (why isn't this stickied?). 1990 EX500, 22k miles, very well abused by po's, po's, po's, no telling how many.

After leaving it sitting with oil in the cylinders from a compression test (100 psi max both cyls) 4 days ago, I noticed that same oil seeping out between the head and the cylinder body today... :p So, it's a no brainer, I've got to do the head gasket, valves etc.

I'm not a mech noob, but I am a ex500 noob. Can the head assembly be removed without removing the entire engine from the bike?

Also... re painting with whatever color.. referring to painting the new head gasket itself?

Finally a reason to clean out my basement work shop.

Thanks in advance.
 
#29 ·
Yes the head And cylinders can be removed in the bike. Re use the old head gasket by cleaning it with laquer thinner and steel wool till it shines. Then re spay a single coat of any color paint on each side No 2 coats will not be better.

Lap bot the head and cylinders Critical

FOG
 
#30 ·
I need to do this and I have a question. In the pictures with the write up it looks like what is under the cylinder head where the pistons go has been removed as well(sorry i don't know the name of that part of the motor). Would it be ok to lay the lapping plate on top of that part while its still attached to the bottom of the motor? My idea would be, lay the cylinder head on the lapping plate and lap it. Then put the lapping plate on the motor part with a weight on top of it to apply pressure. Then move it back and forth while twisting(to get closer to a figure 8 motion).

Would doing that to the bottom part be advantageous or do you really have to remove it as well to accomplish an improvement?

Thanks!
 
#32 ·
So once I remove the cylinder block and I have lapped it I just slide the cylinder block back onto the pistons. In my service manual it references a "Piston Ring Compressor". Is there a specific size or type of compressor I would need to get? Are they a fairly common tool or will I need to order it? Other than that it looks pretty straightforward.

Thanks again, and quick response too :)
 
#33 ·
Get 2 large hose clamps the kind that can be opened these are wide enough to compress all the rings. also get a wooden paint mixing stick. Cut it in half then set is across the block surface undr the piston skirts ,turn the crank so tha the pistons clamp down on the sticks. This will hold them stable to make slidding the cylinders down over them easier.

FOG
 
#35 ·
Some new info on head gasket repair.
I had a 2002 Cadillac sedan De ville with the dreaded North-star head gasket leak. This was exactly the same as the EX high pressure gasses from combustion over pressurizing the Rad cap then blowing out the coolant. There is no mechanical fix for this as the head bolts are the self tapping type and once removed the block is destroyed.
SO I have a $8000.00 car worth about 500 from the junky.
I see on the internet some head gasket repair goop for 130 bucks ,that says guaranteed to fix Caddies. Hey what have I got to loose.

The process is not simple. Involves determining what cylinder/s is the culprit first Then you must run the engine till it full hot the drain some coolant out replace it with the goop the run the engine again a elevated RPM for 15 min. Then shut it off over night to allow the cooling engine to suck the goop into the leak. then drain it all out and re fill with new and go.

Guess what ? It worked. I drove the piss out of it for a week and it never got over normal or lost a drop of coolant.
I later sold the car for a fair price with a clean conscience. (I told the buyer of the fix).

FOG
 
#36 ·
FOG said:
I see on the internet some head gasket repair goop for 130 bucks ,that says guaranteed to fix Caddies. Hey what have I got to loose.



FOG
What's this stuff called? I have an old 4 wheeler that might benefit, plus I'm curious. Also, thanks for the instructions on lapping, VERY good information. The internet does have some good qualities after all.
 
#37 ·
I had to Google it up , but it's called Heal -a- Seal
http://www.heal-a-seal.com/NorthStar.html
I swear the stuff worked. but you must follow the directions. Basically you get it in the cooling system under pressure the release the pressure in the cylinders (remove the plug) then let it seep into the leak where it hardens via catalytic action

Wala! Fixed.

FOG
 
#40 ·
Well im not doing anything, just heard it like 100 times, "if you remove pistons from cylinders you need new rings, otherwise its gonna drink oil", from older mechanics around here.

Last time I was disasembling one engine i removed piston pins, and left pistons in the cylinder, harder to disasemble, but much easier to reasemble when you dont have piston rings compressor.
 
#42 ·
Yeah I did that when I was rebuilding my engine, pushed first ring in groove and pushed piston in cylinder, lead angle makes it possible, then second ring, then third. And then the same for second cylinder, watching carefully not to pull the first one out. It is a delicate job, but can be done, carefully.
Ring compressor, even DIY version, makes it A LOT easier.

So no need for new piston rings, see that one is an eye opener for me, cause I was allways like "why?".
I understand if you pull out pistons, and the rings are a bit worn, that they will not be as good when you put them back in as they were before removal. So you must change them. But you would have to change them anyway in 10-20k, and they are not such a great expense. If they are good on removal, why not? I changed mine some three years and 15k ago, if had to do lapping of head now, why I could not "reuse" piston rings, I mean, how bad can they be?
 
#43 ·
TIP:
turn the crank until both pistons are level,
Then slip two paint mixing sticks under the skirts.
Turn the crank to tighten them down to the sticks. This will hold the pistons still .
You should already have the rings compress with the Hose clamps

Now you can drop the cylinders down over both pistons in one fell swoop.
Then remove the hose clamps.

FOG
 
#46 ·
FOG said:
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)
FOG, by "spray enamel", do you mean any spray paint? (I've been told they all contain a bit of enamel),
or do you mean actual enamel spray? (I've only been able to locate white enamel spray for bath fixes, but I'm pretty sure that's not the stuff you meant :) )



FOG said:
You ought to re- fresh your valve seats now too.
Should the valves be re-freashed only if there's a leak, or in any case?
what valves lapping compound do you advise to use?
 
#49 ·
Yesterday I picked up a piece of granite for free from a local granite counter top co. It was about 2 square feet. they had a pile of that stuff that they would gladly give you.
BTW I cut the thing with my skill saw using one of the tile cutting diamond blades, like a piece of wood.

FOG
 
#50 ·
FOG said:
Yesterday I picked up a piece of granite for free from a local granite counter top co. It was about 2 square feet. they had a pile of that stuff that they would gladly give you.
BTW I cut the thing with my skill saw using one of the tile cutting diamond blades, like a piece of wood.

FOG
Hi FOG, i'm about to use your method on my '98 ninja 250, the cylinder block it's similar to the ex500's. I need to get both surfaces lapped(?) and i'm gonna use a thick piece of glass. Already cleaned and painted the gasket. Expect more pics and updates!! Thanks in advance, greeting from Patagonia Argentina.

https://www.dropbox.com/s/zhi80b9curpmbw1/Foto 26-04-14 22 11 16.jpg
https://www.dropbox.com/s/sbf69beg538ppg9/Foto 26-04-14 22 11 39.jpg
 
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