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Author Topic: Cylinder head what am I doing wrong  (Read 7500 times)

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Offline Chrisgg90

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Cylinder head what am I doing wrong
« on: February 19, 2016, 02:23:10 PM »
I'm just rebuilding the top end of my 1988 500 after barrel was away to get welded due to being cracked. Every time I put the cylinder head on and torque it down and fill the coolant its seaping out the head gasket. Wasn't doing this before being stripped it down.

I'm using new gaskets and the head is cleaned with all old gasket removed tightened to 25 nm in a crisscross pattern. The head can't be warped as. It's been stitting on the bench the last couple months.

Any ideas ?
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Offline kxpegger

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Re: Cylinder head what am I doing wrong
« Reply #1 on: February 19, 2016, 03:42:35 PM »
If the cylinder studs were screwed in to tight this can raise or deform the cylinder material area and cause the gasket to not seal. Also depending on the manufacturer the gasket can be directional meaning one side goes up or down. Other than the mating surfaces not being square this is all I have?
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Offline sandblaster

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Re: Cylinder head what am I doing wrong
« Reply #2 on: February 19, 2016, 03:55:59 PM »
Here is what I would do.
Remove head.
Remove gasket.
Remove studs.
Countersink the stud holes just a smidge.
Lap the head to the cylinder using Timesaver.
Clean the parts to perfection.
Install new studs and torque them to the correct value.
Install the head using a OEM or Cometic gasket.
Torque the head to the correct value.
Fill radiator with the correct amount of Royal Purple's Purple Ice.
Burp it.
Start it and ride about 30 minutes.
Check the torque of the head bolts.
Problem solved, Go riding  8-)
« Last Edit: February 19, 2016, 04:24:02 PM by sandblaster »
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The four stroke engine: That's one stroke for producing power and three for wearing the engine out.

Offline Chrisgg90

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Re: Cylinder head what am I doing wrong
« Reply #3 on: February 19, 2016, 04:34:10 PM »
Quote from: sandblaster on February 19, 2016, 03:55:59 PM
Here is what I would do.
Remove head.
Remove gasket.
Remove studs.
Countersink the stud holes just a smidge.
Lap the head to the cylinder using Timesaver.
Clean the parts to perfection.
Install new studs and torque them to the correct value.
Install the head using a OEM or Cometic gasket.
Torque the head to the correct value.
Fill radiator with the correct amount of Royal Purple's Purple Ice.
Burp it.
Start it and ride about 30 minutes.
Check the torque of the head bolts.
Problem solved, Go riding  8-)


Cheers sandblaster. What do you mean countersink the stud holes ?
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Offline sandblaster

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Re: Cylinder head what am I doing wrong
« Reply #4 on: February 19, 2016, 04:59:07 PM »
Get a countersink, put it in your drill, and countersink all the stud holes approximately 1/16" deep.



That way any material that is pulled up from over torquing your studs is removed.
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The four stroke engine: That's one stroke for producing power and three for wearing the engine out.

Offline Chrisgg90

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Re: Cylinder head what am I doing wrong
« Reply #5 on: February 19, 2016, 11:26:54 PM »
Ah get you now.. Thanks
« Last Edit: February 20, 2016, 12:18:24 AM by Chrisgg90 »
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Offline sandblaster

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Re: Cylinder head what am I doing wrong
« Reply #6 on: February 20, 2016, 01:53:01 AM »
Thank Motorrad, he turned me on to the issue 8-)
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The four stroke engine: That's one stroke for producing power and three for wearing the engine out.

Offline Foxx4Beaver

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Re: Cylinder head what am I doing wrong
« Reply #7 on: February 20, 2016, 02:10:28 AM »
Unless you have to send the cylinder out, like you did this time...don't bother pulling the head off.
Next time you need to pull the top end apart...whether it be to check side play in the big end bearing, throw a new piston/rings in it, or just re-ring it....leave the head right on it.
You will have to pull the motor out of the cradle, which is no big deal...but it'll save you from having to buy head gaskets, and you won't have to worry about lapping the head and cylinder due to head warpage....and possibly going through this again.
Unless I'm sending my cylinder out to be re-plated/welded....I never take the head off...much easier.
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Offline Chrisgg90

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Re: Cylinder head what am I doing wrong
« Reply #8 on: February 20, 2016, 09:54:52 AM »
Quote from: Foxx4Beaver on February 20, 2016, 02:10:28 AM
Unless you have to send the cylinder out, like you did this time...don't bother pulling the head off.
Next time you need to pull the top end apart...whether it be to check side play in the big end bearing, throw a new piston/rings in it, or just re-ring it....leave the head right on it.
You will have to pull the motor out of the cradle, which is no big deal...but it'll save you from having to buy head gaskets, and you won't have to worry about lapping the head and cylinder due to head warpage....and possibly going through this again.
Unless I'm sending my cylinder out to be re-plated/welded....I never take the head off...much easier.

Yeah that's exactly what I do but it had to come off because it was going away to be welded. What was worse I had built the whole bike back up again before I refilled the coolant 😭
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Offline Foxx4Beaver

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Re: Cylinder head what am I doing wrong
« Reply #9 on: February 20, 2016, 10:26:10 AM »
yeah, that's a bummer. :lol:
Before I put any plastics or the fuel tank back on...I fill it, then bleed the system.
Then I'll fire it up a couple times and check for any hose or base gasket leaks. Then I'll bleed the system one more time, lifting the front wheel off the ground to about waist height(another Motorrad procedure), to be sure all the air's out....then finish putting it together.
Doing it this way has worked well for me the past few years.
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Offline Chrisgg90

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Re: Cylinder head what am I doing wrong
« Reply #10 on: February 21, 2016, 05:38:01 AM »
What's the torque value for the studs ?
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Offline Foxx4Beaver

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Re: Cylinder head what am I doing wrong
« Reply #11 on: February 21, 2016, 05:46:19 AM »
are you asking about the cylinder/head studs themselves, or the torque of the nuts?
I snug the studs into the cylinder at about 15 lbs, but also seal them in with yamabond4.

18 ft lbs for the head nuts
25 ft lbs for the cylinder nuts
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Excuse me, ma'am...but you've got extremely nice legs!!!...what time do they open???                                                                                                               https://www.youtube.com/watch?v=n8tCgN3aryQ

Offline Chrisgg90

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Re: Cylinder head what am I doing wrong
« Reply #12 on: February 21, 2016, 05:50:46 AM »
Yeah its studs them selves i was talking about. Thanks for that
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Offline Foxx4Beaver

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Re: Cylinder head what am I doing wrong
« Reply #13 on: February 21, 2016, 05:52:52 AM »
no more than 15 lbs...or you'll be screwed if you pull the threads....start with 12lbs, and see how it feels, if it feels too tight, stop there.
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Excuse me, ma'am...but you've got extremely nice legs!!!...what time do they open???                                                                                                               https://www.youtube.com/watch?v=n8tCgN3aryQ

Offline Chrisgg90

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Re: Cylinder head what am I doing wrong
« Reply #14 on: February 21, 2016, 11:33:21 AM »
Well got it built back up tonight and and seems all good hopefully will run it hopefully next weekend see how it is. Thanks for the help guys
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