Topic: MLS Gasket Reuse

[BRAD CHIEDUCH]

The topic of reusing an MLS head gasket has been discussed on the forum before and guys seem to get away with it, but I would like to share my experience.  The engine has been totally gone over, Mike Rieck did the head work and the boys at Cyclex did the cylinder work – excellent work by all!  I have had the head on and off several times doing valve clearance checks etc. and have used the same gasket with the intention of putting in a fresh gasket on final assembly.  Now the last time I put the head on I noticed daylight peaking through the gasket at the front corner of cylinder #4.  I was able to sneak a 0.002” feeler gauge in about ½” in a few places around the perimeter of the gasket.  I took the head off and did all the usual checks i.e. straight edge on the cylinder surface, deck of the head, checked locating dowel height – everything was perfect!  I then put the head on without the gasket (still with locating dowels in place) and there are no gaps anywhere – again everything is perfectly flat and tight.  I have come to the conclusion that reusing the MLS gasket more than once compresses the corrugations in the gasket and thus can create gaps like I have experienced.  So, if I had to offer advice, I would not reuse an MLS gasket.

[PeWe]

I reused an MLS on my 836 build. I guess it had been running 3000km or so. No leaks.
The rivets are still keeping plates together?
Rivets can interfere with the mating surfaces causing huge gaps. 
I drilled small dents on both head and block mating surfaces were rivets were located. I had hammered them flat but needed extra room just for sure.

If rivets are removed, the different MLS layers have moved internally sideways, not exactly stacked as when riveted?

Same head sit now on Mike Rieck Billet block. The mating surface is exactly shaped as the gasket leaving rivets outside.
Never opened after assembly which is dry without leaks after 15.000 km.

[DaveBarbier]

Were you torquing the head down each time? When you saw daylight through it the head was torqued down? I initially thought of rivet interference too but maybe not likely. I just don’t see how this would happen unless there was a mistake in assembly or something got in between the layers of the gasket. If anything, the torquing down would flatten out the gasket more. When I was checking my motor for valve clearance I used the same gasket but didn’t go down to full torque. Maybe like 15lbs instead of 22lbs or whatever my torque spec was. Same gasket is in there now after a couple years and it’s bone dry. What does the gasket look like alone?

[BRAD CHIEDUCH]

I had the same thought on the gasket rivet interference but I took a Dremel and relieved the head in those locations and it made no difference.  Each time the head was torqued to 20 ft-lbs and it was just on the last go around that I noticed the gap.  I'm going to take my micrometer and measure the gasket thickness in some spots and check for something stuck between the layers of the gasket.  Something just isn't making sense. 

[BRAD CHIEDUCH]

Today I went over everything again.  Checked head and cylinder flatness with a longer straight edge - no problem with flatness.  Double checked dowel pin height - that's not the problem.  Ground and removed the brass rivets from the rear of the gasket and took a punch and flattened the front rivets.  Installed the gasket and retorqued the head to 20 ft-lbs and the problem still exists.  Maybe with repeated torqueing the head gasket material has strain hardened and lost its squish.  I have surrendered to the fact that I will just have to try a new gasket and see if the problem persists.

[beemerbum]

Today I went over everything again.  Checked head and cylinder flatness with a longer straight edge - no problem with flatness.  Double checked dowel pin height - that's not the problem.  Ground and removed the brass rivets from the rear of the gasket and took a punch and flattened the front rivets.  Installed the gasket and retorqued the head to 20 ft-lbs and the problem still exists.  Maybe with repeated torqueing the head gasket material has strain hardened and lost its squish.  I have surrendered to the fact that I will just have to try a new gasket and see if the problem persists.

Why would anyone ever re-use a head gasket? Are they in short supply like toilet paper?

[BRAD CHIEDUCH]

Why would anyone ever re-use a head gasket? Are they in short supply like toilet paper?

I agree, I was just using an old gasket for checking measurements.  They might not be scarce but they cost as much as toilet paper! 

[PeWe]

It is very convenient to reuse a gasket and save $100USD. More if living in Europe with more shipping and VAT.

I have talked to a guy working with different motorcycle engine tuning and restores that do this on regular basis. Worked with CB750 since early 70's, good head porting guy.

If gasket is really used in an running engine so viton rubber has disappeared (by heat) he scrub it clean and spray  Loctite 3020 spray. Photo from the shop. Same with RCS base gaskets.

This MLS must have a problem, something between layers or damaged.

[rotortiller]

I have a hard time reusing cylinder, head gaskets and associated seals on a SOHC. While no doubt some people have gotten away with it, to me I'd be pretty upset if it sprung a leak etc after all that work.  Sure you may have to spend a bit of gasket money however if you put a high value on your care and effort it may be unwise. I have watched shortcuts work out in life and I have seen an equal amount of frustration in doing the job twice. If it were an easy accessible gasket like a side cover I'd not think twice about reusing a good looking gasket. I guess it boils down to risk, balancing economics and professionalism. If you took your car or bike to a garage and the tech carefully reused the gasket only to spew oil  on the way home what would you do? What if all that gasket snot sealing oil also seals an oil passage? Head gasket recycling process to me borders on being "Mickey Mouse" however if you get away with, it all the more power to you.

[BRAD CHIEDUCH]

I did a little more investigating to try and find the root cause to my gasket problem.  I removed the rivets from the gasket and separated the layers for closer examination.  I found the embossment in the gasket spacer around the cylinders to be compressed in a small area at the front of each cylinder (shown by #1 in photo).  Compared to the embossment towards the rear of the cylinder (#2), this area has little compression.  It appears that the compressed areas of the spacer were causing the gap problem.  So why did it happen?  Uneven torqueing – perhaps, but I can say I have always followed the torque pattern in the manual and have always torqued from 18-20 ft-lbs.  Manufacturing error is possible.  I discussed with Cometic tech support, and they were a bit surprised by the low torque value.  However, if the torque is insufficient, I would still expect the crush on the gasket to be uniform provided the gasket seating pressure is uniform.  I’m just glad to have found the problem and all I can do is replace the gasket and check for gaps – hope the problem goes away.

[PeWe]

Knock pin lenghts OK, not too long? 2, 1 in each corner. Hole depths differs on heads and cyl blocks. Must be measured and compared with pins.

Not used oil return o-rings with eventual 8 pins as stock use?

I used clean MLS, plus 2 o-rings for oil feed just for sure since they could be used.

All holes for oil feed and returns have ridges around to seal on my MLS gaskets.
I'm convinced it will seal fine without any o-rings.

I tightened 27-28Nm (20- 20.6 Ft lbs). Kibblewhite HD studs.
I tightened stock studs with same torque many years ago.
Not more.

[DaveBarbier]

Knock pin lenghts OK, not too long? 2, 1 in each corner. Hole depths differs on heads and cyl blocks. Must be measured and compared with pins.

He installed with no gasket and it sat flush.

I used clean MLS, plus 2 o-rings for oil feed just for sure since they could be used.

All holes for oil feed and returns have ridges around to seal on my MLS gaskets.
I'm convinced it will seal fine without any o-rings.

The MLS is designed to not use the o-rings. The embossments seal well. My 650 has no o-rings as recommended by Dynoman and it’s bone dry.

[BRAD CHIEDUCH]

Thanks Dave for answering PeWe's questions.  I have ordered a new base and head gasket and will try again.  However, I'm convinced the head is sitting high on the embossed surfaces of the gasket and it is not crushing down.  To satisfy my curiosity, I am wondering if anyone out there using an MLS gasket is willing to check for gaps on their bike.  Try the corners of the head and see if you can sneak a 0.002" feeler gauge in there about 3/4".  I have a hunch the gap is there.  Is it possible that I'm the first to check?   

[seanbarney41]

Here is a thought....
I have seen where oem combustion chambers are not necessarily perfectly round, plus bolt holes on aftermarket gaskets allow a considerable amount of slop...perhaps gasket was slipped one way when first torqued and is not aligning the same way the second time causing work hardened ridges that don't want to crush down?

[DaveBarbier]

Thanks Dave for answering PeWe's questions.  I have ordered a new base and head gasket and will try again.  However, I'm convinced the head is sitting high on the embossed surfaces of the gasket and it is not crushing down.  To satisfy my curiosity, I am wondering if anyone out there using an MLS gasket is willing to check for gaps on their bike.  Try the corners of the head and see if you can sneak a 0.002" feeler gauge in there about 3/4".  I have a hunch the gap is there.  Is it possible that I'm the first to check?   

Checked my 650 with an MLS gasket and there’s no gap. Can’t stick any feeler gauge in there. Not even .001”

[BRAD CHIEDUCH]

Here is a thought....
I have seen where oem combustion chambers are not necessarily perfectly round, plus bolt holes on aftermarket gaskets allow a considerable amount of slop...perhaps gasket was slipped one way when first torqued and is not aligning the same way the second time causing work hardened ridges that don't want to crush down?

I laid the gasket on the head and the embossed area is well outside of the combustion chamber, so that doesn't appear to be a problem.

[BRAD CHIEDUCH]

Checked my 650 with an MLS gasket and there’s no gap. Can’t stick any feeler gauge in there. Not even .001”

Thanks for checking Dave, now I know what to expect when I change the gasket.

[scottly]

Knock pin lenghts OK, not too long? 2, 1 in each corner. Hole depths differs on heads and cyl blocks. Must be measured and compared with pins.