How to: Properly install head gaskets


9 replies to this topic
  • WRetard

Posted August 25, 2009 - 10:10 PM

#1

I have seen so many posts about failing head gaskets, that I can no longer be bothered writing out half a page of help for every one I see.

So here's a guide I wrote to help people having issues.

Check your head with a straightedge and feelers for warpage. Also look for any scratches.

Resurface the head with 600 grit wet and dry sand paper and WD40 on a flat piece of glass IF it is out of spec. Resurface in a figure of '8' motion, rotating the piece 90 degrees every now and then for an even surface. You will need to remove the centre intake valve as it sits slightly below the deck surface. It is also a good idea to briefly resurface the top of the cylinder.

Trial fit the gasket to make sure that the bolt holes and dowels/coolant dowels all line up. The gasket must sit flat, if it bows a little because the holes aren't spot on, you can carefully modify the dowel/bolt holes in the gasket with a dremel. Mismatched dowel holes will apply hundreds of pounds of nasty horizontal force once the head is torqued down. It's a recipe for failure.

Use brake cleaner (best solvent ever) to THOROUGHLY clean the gasket, cylinder and head surface, it MUST be squeaky, squeaky clean, no finger prints, no oil, no nothing. Also don't bother with gasket compounds, they tend to be a common solution for people that don't install gaskets correctly. These metal head gaskets are designed not to be used with other compounds.

Carefully fit the cylinder and head without touching or getting oil on any gasket surfaces. Drop the head bolts into their bolt holes.
Place a socket on the head bolts and finger tighten so the head is sitting level, then torque the head down in small increments of 5 ft lb's til you get to 27ft lb (from memory thats what YZ/WR250F head bolts are torqued to).

Every time you tighten a bolt, it loosens the next closest bolts, so if you torque each head bolt once, you will end up with loose ones.
So for each 5 ft lb graduation, keep torquing in a criss cross pattern until all the bolts are equal tension, then adjust your wrench another 5 ft lb and repeat. This endures your whole head is evenly torqued down.

Once it is all together, run the engine for say 3 heat cycles (heat up, cool down) with PLAIN WATER only, no coolant, to let the head gasket bed in or 'settle'.
Chemicals in coolant are actually slightly harmful to new gaskets. Once you have heat cycled it, drain the water out and put your favourite coolant in. Never leave plain water in the cooling system for more than a day, it will corrode aluminium and rust steel, and it is prone to freezing which WILL crack your head and possibly cylinder, believe me I had this happen once and it was not fun :ride: .


I hope this helps you guys out.


Additional info from TT members:

William1

Also, not manufacturers torque spec, manuals are not always accurate. Think about the bolts. If you know you have everything right and still have gasket failure (not due to a massive overbore and resulting minimal wall thickness) the torque specs may be too low.

Finally, be sure the threads are perfect on the bolt and case. If the torque specs specify oiled threads, use oil, not anti-seize. If dry, make the treads truly dry. Torque in small steps, in a crosswise pattern. Use a good wrench.



  • yamaha227

Posted August 25, 2009 - 11:22 PM

#2

Some good tips there and pretty much exactly the same way i install my big bore head gaskets :ride: . I use 400 grit wet and dry for the cyl/head resurfaceing on a flat piece of glass. After trying gasket sealing compunds, a dry installation seems to be more reliable for me too.

  • William1

Posted August 26, 2009 - 02:56 AM

#3

I'll add that I use a coating of permatex copper coat on the head gasket 24 hours or so prior to assembly. I have never had a leak.

Also, not manufacturers torque spec, manuals are not always accurate. Think about the bolts. If you know you have everything right and still have gasket failure (not due to a massive overbore and resulting minimal wall thickness) the torque specs may be too low.

Finally, be sure the threads are perfect on the bolt and case. If the torque specs specify oiled threads, use oil, not anti-seize. If dry, make the treads truly dry. Torque in small steps, in a crosswise pattern. Use a good wrench.

  • WRetard

Posted August 26, 2009 - 07:35 PM

#4

I'll add that I use a coating of permatex copper coat on the head gasket 24 hours or so prior to assembly. I have never had a leak.

Also, not manufacturers torque spec, manuals are not always accurate. Think about the bolts. If you know you have everything right and still have gasket failure (not due to a massive overbore and resulting minimal wall thickness) the torque specs may be too low.

Finally, be sure the threads are perfect on the bolt and case. If the torque specs specify oiled threads, use oil, not anti-seize. If dry, make the treads truly dry. Torque in small steps, in a crosswise pattern. Use a good wrench.


To each their own, the gaskets have a coating which bonds to the head/cylinder surface once heat cycled. The manufacturers don't use gasket compound from the factory and it's rare as hell to get a failed head gasket from the factory. I put 90% of gasket failures down to operator error. I'm not saying your method is wrong, there are many ways to skin a cat, I just find it unnecessary personally. But whatever works for you :ride: .

Your other tips are also very good, may I put them in my original post with reference to you?

  • William1

Posted August 27, 2009 - 03:01 AM

#5

No, I hear you about adding crap to gaskets. A head gasket is the only one on a bike I'd do it to. I do it on all bikes, whether it needs it or not. Meaning on some over bores, the mating surface it so minimal, it needs every bit of help it can get. So to prevent issues, I simply do all head gaskets (I should clarify, all 4S, not 2S).

Please feel free to use my words, I find that a compliment and appreciate you asking. :ride:

  • WRetard

Posted September 04, 2009 - 03:20 AM

#6

Just wondering if mods want to sticky this as there seems to be questions asked multiple times per day...

  • DieselSJ

Posted September 04, 2009 - 01:21 PM

#7

Finally, be sure the threads are perfect on the bolt and case.


I always run a tap through the threads on the case and clean with brake clean, and clean the bolt threads thoroughly. You should be able to easily thread the bolt all the way in by hand. If you can't get the bolt all the way in with just your fingers, then things are not clean enough.

  • yamaha227

Posted October 01, 2009 - 10:47 PM

#8

To each their own, the gaskets have a coating which bonds to the head/cylinder surface once heat cycled. The manufacturers don't use gasket compound from the factory and it's rare as hell to get a failed head gasket from the factory. I put 90% of gasket failures down to operator error. I'm not saying your method is wrong, there are many ways to skin a cat, I just find it unnecessary personally. But whatever works for you :busted: .

Your other tips are also very good, may I put them in my original post with reference to you?



WRetard, when you say you re-surface your head do you remove the exhaust flange lower stud and the 2 studs on the L/H side of the head aswell as the centre intake valve. As last time i tried to re-surface my head with some wet and dry on a plate of glass, these studs were getting in the way of doing the whole surface properly.
I tried to remove them with the 2 nuts tightened together method but they were too tight and i couldnt get them out. Got any tips? Maybe i need to add some heat to the area to get them out?
Reason i ask is im having trouble with my head gasket sealing of late, last one only lasted 15 hours, and last time i had the head off i noticed some pitting on the head so im thinking i will need to get it resurfaced properly at a cylinder head reconditioning shop this time.

  • WRetard

Posted October 02, 2009 - 01:03 AM

#9

WRetard, when you say you re-surface your head do you remove the exhaust flange lower stud and the 2 studs on the L/H side of the head aswell as the centre intake valve. As last time i tried to re-surface my head with some wet and dry on a plate of glass, these studs were getting in the way of doing the whole surface properly.
I tried to remove them with the 2 nuts tightened together method but they were too tight and i couldnt get them out. Got any tips? Maybe i need to add some heat to the area to get them out?
Reason i ask is im having trouble with my head gasket sealing of late, last one only lasted 15 hours, and last time i had the head off i noticed some pitting on the head so im thinking i will need to get it resurfaced properly at a cylinder head reconditioning shop this time.


Hmmmmm try using some WD40 to loosen the studs, yes I removed those three studs to resurface, there's no other way.

You could grind flats into the original studs and use vice grips to undo them, but you will need to replace the studs with new ones.

  • yamaha227

Posted October 04, 2009 - 01:32 AM

#10

Hmmmmm try using some WD40 to loosen the studs, yes I removed those three studs to resurface, there's no other way.

You could grind flats into the original studs and use vice grips to undo them, but you will need to replace the studs with new ones.


Yeah will give it a crack, but if no luck will prob leave it up to the machine shop to do.

What year model is yours and what jetting are you running?

Thinking mine may be running a little lean and could be getting a bit hotter than normal.




 
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