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Author Topic: MLS Head Gasket and O-Rings  (Read 2569 times)

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Offline DaveBarbier

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MLS Head Gasket and O-Rings
« on: November 06, 2016, 05:41:37 PM »
Decided to venture out of the safety of my build thread for this one. Hey everyone, in assembling my 650 motor with an MLS gasket I've found that the top end oiling holes from cylinders to head won't fit an o-ring. The gasket shrouds the o-ring recess enough that I don't think any o-ring, no matter the size, would work there.

Are o-rings required if I'm using an MLS gasket? It seems my options are:
1. use no o-ring
2. get a custom MLS gasket that can allow for the OEM o-ring (unlikely)
3. enlarge the holes on my MLS gasket to accommodate said o-ring (not ideal as there's an embossed ring that surrounds the oil hole which would need to stay)

Thoughts? Surely someone has used an MLS gasket on a 650 or 550 (same issue would arise on that motor) that can comment.

Thanks!
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Offline SOHC4 Cafe Racer Fan

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Re: MLS Head Gasket and O-Rings
« Reply #1 on: November 06, 2016, 07:19:11 PM »
I help up on getting the MLS gasket and installed the 674 kit gasket for now.
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Offline Don R

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Re: MLS Head Gasket and O-Rings
« Reply #2 on: November 06, 2016, 08:10:32 PM »
 MLS shouldn't need the o rings but I'm not a 650 guy.
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Offline RAFster122s

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Re: MLS Head Gasket and O-Rings
« Reply #3 on: November 06, 2016, 08:54:11 PM »
Which orings on the exploded parts diagram?  Do they surround bolts or just ports from block through cylinders to the head?  Can you post the parts exploded diagram and provide the # of the part?
The leakfree head gasket thread that Branden posted addresses this issue on the 750 gaskets.  The orings may not be needed...Calj and MReich and HondaMan would be able to answer.
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Offline PeWe

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Re: MLS Head Gasket and O-Rings
« Reply #4 on: November 07, 2016, 04:00:55 AM »
CB750: I used 2 o-rings for the oil feed to head with 65mm MLS (836) and later 68mm MLS (900cc). No oil leak
I have had thoughts that these are not needed since there are sealing ridges around these 2 holes on both MLS I have.
- It would be fine to have this confirmed.  (I'll skip them on next assembly this winter with wider bores)

- Base gasket  "Rubber Coated Steel Viton" must have o-rings as std fiber, right?

MLS
Important to check if the rivets keeping the plates together are free or squeezed between head and cyl block. I hammered mine flat plus drilled small dents into head and cyl block to ensure no rivet causing a gap as it did first time I bought an MLS ending up in fiber. MLS is better when know how to do. Open head and reuse the gasket, no problem.
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Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
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http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline DaveBarbier

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Re: MLS Head Gasket and O-Rings
« Reply #5 on: November 07, 2016, 04:19:28 AM »
Part number 4 are the o-rings I'm talking about. They go into a recess on the head, which in this picture, are the ones colored black. Note that the dowels that are floating right next to the o-rings don't go together. The dowels go into a bolt hole and no oil goes through them.
http://www.cmsnl.com/honda-cb650sc-nighthawk-1982-c-usa_model475/partslist/E++05.html#results

I found a picture online (not my motor) of a close up of the o-ring. You can see the o-ring in place and that the head gasket here has a hole large enough so the o-ring can do it's job.

https://lh5.googleusercontent.com/-MTEX53CnIv4/UrJBlRStqPI/AAAAAAAABrI/n_f6_Kvr2Ms/w1437-h1078-no/20131218_165238.jpg

And thanks Pewe, I did verify that the rivets are outside and won't interfere with sealing.
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Offline DaveBarbier

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Re: MLS Head Gasket and O-Rings
« Reply #6 on: November 07, 2016, 04:27:12 AM »
Quote from: CB750 Cafe Racer Fan on November 06, 2016, 07:19:11 PM
I help up on getting the MLS gasket and installed the 674 kit gasket for now.

Yeah, I'm actually using that gasket to mock things up. Seems like there's nothing wrong with using it. But people love these MLS gaskets. To me they're frustrating right now but that's just because I haven't used them ever and don't know their nuances. I'll get it sorted out soon enough.
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Offline PeWe

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Re: MLS Head Gasket and O-Rings
« Reply #7 on: November 07, 2016, 09:36:08 PM »
About MLS and  oil feed o rings... I will use those 2  with MLS head gasket in next CB750 build too.
I asked a well known guy on this forum with experience.
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CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline DaveBarbier

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Re: MLS Head Gasket and O-Rings
« Reply #8 on: November 08, 2016, 04:32:24 AM »
Quote from: PeWe on November 07, 2016, 09:36:08 PM
About MLS and  oil feed o rings... I will use those 2  with MLS head gasket in next CB750 build too.
I asked a well known guy on this forum with experience.

Yeah I noticed that most of the 750 guys mention using 2 o-rings with an MLS gasket, but omitting the others. I'm not very familiar with the 750 so I'm not sure which o-rings they're keeping and which are being removed and what makes those o-rings different from each other.

Also, if I were to use these o-rings then I'd have to enlarge the holes on the gasket. Or possibly get a new MLS gasket with larger holes...not sure if those exist.
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Offline PeWe

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Re: MLS Head Gasket and O-Rings
« Reply #9 on: November 08, 2016, 04:56:18 AM »
It is the 2 o rings for oil feed. There are wider holes for them
see my photos with MLS + o rings and without and no o rings
http://forums.sohc4.net/index.php/topic,161372.msg1855875.html#msg1855875

The photo here on a CB550 cylinder show same kind of holes for o rings but in the outer ends. CB750 has in the center.  Intake side on each side of cam chain tunnel.
I should use o-rings here
http://picclick.co.uk/Honda-CB550-Cylinder-Block-C-w-Pistons-600cc-331986781092.html#&gid=1&pid=1
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CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline DaveBarbier

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Re: MLS Head Gasket and O-Rings
« Reply #10 on: November 08, 2016, 05:13:49 AM »
Yeah, the 650 has the same o-ring holes as the 550. If the holes in the gasket were large enough I wouldn't even have asked the question. I would have just used the o-rings and that's that. But they won't fit with this gasket so I wasn't sure if it was required. Maybe I could get smaller o-rings? But I don't want to start doing some makeshift stuff and end up blocking the oil gallery. I'm also not about to start drilling into this gasket to enlarge the hole.

I'd love it if someone can comment on what they did with their MLS and 550 or 650 and how it's holding up.
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Offline DaveBarbier

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Re: MLS Head Gasket and O-Rings
« Reply #11 on: November 08, 2016, 03:03:33 PM »
Buzz over at Dynoman said that the o-rings aren't used with this gasket. He goes on to say the embossing around the hole takes the place of the o-ring.

I'll post back here in about 7 months to say whether or not it sealed, haha.
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Offline bwaller

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Re: MLS Head Gasket and O-Rings
« Reply #12 on: November 08, 2016, 03:41:14 PM »
This should clear things up Dave..... ;D Can you believe it I found this picture and it couldn't be more useless for you! Me too, I cannot remember to save myself whether or not the gasket had a smaller than normal hole for the oil feed but I expect so.

By no means enlarge that hole, any metal grit will embed in the viton and that would be bad.


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Offline DaveBarbier

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Re: MLS Head Gasket and O-Rings
« Reply #13 on: November 08, 2016, 04:18:50 PM »
HAHA! That's hilarious. The cropping is perfect. You can just make out the edge of the embossing of the oil hole on the left. Thanks for nothing Brent, haha.

Obviously I'm hoping this won't leak, but if it does, I'm tearing it down and doing the external oiling mod.
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Offline flatlander

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Re: MLS Head Gasket and O-Rings
« Reply #14 on: November 08, 2016, 08:29:51 PM »
i found this pic of the gasket on the 550. now for the life of me i can't remember if i put that o-ring in there or not and can't find a pic that would show it :(
but if it's of any help, i don't have any leak and oil definitely gets into the head.

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Offline DaveBarbier

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Re: MLS Head Gasket and O-Rings
« Reply #15 on: November 09, 2016, 05:19:34 AM »
Ok, well as of now I am not going to put the o-ring in. So, if in the future someone uses this as a reference, no o-ring.

Thanks for the photos guys.
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