Topic: 79 CB650 The Mayor - Revive and Freshen Up

[DaveBarbier]

I have always wondered why these kits never include the rubber pucks. Doesn’t matter as I just installed some the other day right before I fired it up to see the head gasket was leaking. I’ll just reuse them. I did add some non hardening sealant to them but I don’t think it would be an issue.

[grcamna2]

Yeah !! You located the complete top-end OEM set  Wonderful 
OEM Rules ! 

[DaveBarbier]

Yeah !! You located the complete top-end OEM set  Wonderful 

Totally, he made my week. Now I can delete my notes on all the Honda dealers I was going to call tomorrow, haha.

[onepieceatatime]

Wow, brother, you’re amazing! I just bought it. I looked for full kits first but not sure why this didn’t come up...crazy.

No problem! Glad it helped you out 
I like the old 650s, mainly because my '80 CB650C was my first bike.
There does not seem to be a lot of love for them, but I have been seeing more posts about them lately.

[Kelly E]

Wow, brother, you’re amazing! I just bought it. I looked for full kits first but not sure why this didn’t come up...crazy.

No problem! Glad it helped you out 
I like the old 650s, mainly because my '80 CB650C was my first bike.
There does not seem to be a lot of love for them, but I have been seeing more posts about them lately.

My first bike was also a 1980 CB650 Custom. I got it in May of 1980. I put 38k miles on it in two years.

[onepieceatatime]

My first bike was also a 1980 CB650 Custom. I got it in May of 1980. I put 38k miles on it in two years.

I bought mine as a project in the late 90s I have no idea how many miles are on it, or even how many I have put on it. It was running, but frankensteined with a bunch of parts that didn't belong, and missing other parts.
It is complete and original looking, having returned to an OEM appearance years ago (besides the '81 two tone blue I have on it), "one piece at a time". I also have a correct black tank and side covers that I can put on it, but like the look of the blue. I was going to get it legal again and on the road this year, but because of COVID, I did not. Hopefully next year.

[DaveBarbier]

It’s funny, when I got my 650 for my 674cc 550 frame hybrid there were very few people on here talking about 650’s, but it seems this year there’s been a surge in interest in them. They are a great bike and the motor has some really nice improvements over the 550 with still being essentially a clone. Two things I love are the primary chain tensioner and the removal of that damn plug seal that always gets eaten away by o-ring chains that PO’s have put on and we only discover it once we clean behind the sprocket cover. That, and you’re getting much more HP out of a motor that’s the same weight.

Anyway, this past weekend I moved a wall in my shed to make more useful shop space. Now two bikes fit comfortably. Hoping to start the motor disassembly this coming weekend. But with moving the wall I have some more shop organization to do and don’t want to stir up that much dust with a decapitated 650 laying around. 

[SOHC4 Cafe Racer Fan]

Now you'll have some spares.  All NOS Honda, too!! Nice.

[DaveBarbier]

Now you'll have some spares.  All NOS Honda, too!! Nice.

Exactly. I already have most of the top end stuff enroute but I’ll save it for the next one, haha

[DaveBarbier]

Going to start the head gasket replacement today. Question on something. I’ve removed barrels from the cylinder block before, super easy with an oven. I want to do this to be able to easily clean the base gasket surface. Working around them is a pain in the ass. Of course I’ll label them 1-4 and maybe even orientation. But is it a problem to reinstall the barrels and move on? I vaguely remember someone saying you need to machine the head surface because the top of the barrels won’t sit flush again. Sounds like bs to me but thought I’d ask.

[rb550four]

  I've seen many barrel replacements here on this forum and each time it has happened the deck gets machined.
On the 550's I remove and clean the area where the O rings are around the barrels press them in lightly to be sure they don't get twisted and let the headbolt torque  take care  the seal at the bottom of the barrels ( along with the base seal between crankcase and jugs). I haven't really understood why Iwould remove the barrels unless there was damage o the top of the head where the head gasket will go, then I can see decking, otherwise ,to me , it sounds like an expense and exercise that can be bypassed should there be no damage on the upper surfaces. That's my opinion. Master engine builders will correct me if I'm wrong.I consider damage  requiring replacement of a barrel one of the only 2 reasons to remove them.

[DaveBarbier]

Tore into the top and and got it all apart. Nothing out of the ordinary except that the motor has been apart previously and the head gasket was replaced with a non OEM one. Head gasket looks to be from a 550 or something. The cam chain tunnel is wrong as you can see from the picture. The gasket is overlapping the chain guide and the cutouts are wrong. Another weird thing that I haven’t seen before is, what looks to be, brass sleeves inserted into the oil galleries.

One good thing is the head gasket released from both surfaces fairly cleanly and the base gasket released cleanly from the upper case. It is completely stuck to the cylinders though so that should be fun to remove.

[grcamna2]

Brass sleeves rather than restricters ?

[DaveBarbier]

Brass sleeves rather than restricters ?

It still has the restrictors. Not there on my ‘82 650. Wonder if others have this or if this was a PO thing. Maybe the thought they would get better oiling to the top end if the holes were bigger but then changed their mind and made sleeves to bring it back to where it was...no idea.

[onepieceatatime]

It's been so long since I had the top of my 650, I can't remember. My spare engine is in good running shape, so I don't want to pull the head off. I have another spare, it's an '81 so I would have to swap the head to make it useable on my '80. If I get a chance tonight, I'll pull it out of the parts bike and pull the head to look at it.

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[onepieceatatime]

It's been so long since I had the top of my 650, I can't remember. My spare engine is in good running shape, so I don't want to pull the head off. I have another spare, it's an '81 so I would have to swap the head to make it useable on my '80. If I get a chance tonight, I'll pull it out of the parts bike and pull the head to look at it.

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I checked, and no brass on the '81 engine. I have a cylinder block, with no sleeves and broken fins, I can't remember what year the parts bike was that it came from, but no brass in it either.

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[grcamna2]

Brass sleeves rather than restricters ?

It still has the restrictors. Not there on my ‘82 650. Wonder if others have this or if this was a PO thing. Maybe the thought they would get better oiling to the top end if the holes were bigger but then changed their mind and made sleeves to bring it back to where it was...no idea.

I'm curious if those brass sleeves have been upsetting how the gasket/head was set on top of it ?

[DaveBarbier]

It's been so long since I had the top of my 650, I can't remember. My spare engine is in good running shape, so I don't want to pull the head off. I have another spare, it's an '81 so I would have to swap the head to make it useable on my '80. If I get a chance tonight, I'll pull it out of the parts bike and pull the head to look at it.

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I checked, and no brass on the '81 engine. I have a cylinder block, with no sleeves and broken fins, I can't remember what year the parts bike was that it came from, but no brass in it either.

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Yeah weird. First thing I did was look at the pictures from my first 650 build. It HAS to have been done by a PO. It’s just a tube that, to me, serves no purpose.

[DaveBarbier]

Brass sleeves rather than restricters ?

It still has the restrictors. Not there on my ‘82 650. Wonder if others have this or if this was a PO thing. Maybe the thought they would get better oiling to the top end if the holes were bigger but then changed their mind and made sleeves to bring it back to where it was...no idea.

I'm curious if those brass sleeves have been upsetting how the gasket/head was set on top of it ?

Maybe the pictures make it look like it’s sticking up but the tube is flush with the countersink for the o-rings. But now after having seen this I wonder if the deck has been machined and by how much. I just want to be extra sure the locating dowel pins aren’t too tall now.

[rb550four]

  I thought I'd look up a parts picture/parts list for a 79 650
 https://www.hondapartshouse.com/oemparts/a/hon/506f6f74f8700229747b7bc7/cylinder
not seeing any brass pieces .

[DaveBarbier]

  I thought I'd look up a parts picture/parts list for a 79 650
 https://www.hondapartshouse.com/oemparts/a/hon/506f6f74f8700229747b7bc7/cylinder
not seeing any brass pieces .

Yeah I looked too on CMSNL. I also found the same brass inserts in the galleries on the bottom of the head. I’m not concerned about them really, it’s just making me really pay attention to this top end. So far everything else is normal. I’m mostly really curious why someone would do this. I wonder what the likelihood is that these ARE factory but only on rare occasions where they screw up production. Doubtful though. These are the Japanese we’re talking about.

[RAFster122s]

I seriously doubt it is factory. If it were factory I think you would see exact match on engine and frame and they would do lots of effort to keep them together. Honda doesn't link them and if an engine has a quality problem that wasn't a minor adjustment, they would yank it and drop another in its place.

I think it maybe a screw up of a machine shop and their fix for this.
Got anyway to get a measurement of the ID of the brass inserts?
Curious if the ID is matching stock galley ID or if it is smaller or larger.

[DaveBarbier]

I seriously doubt it is factory. If it were factory I think you would see exact match on engine and frame and they would do lots of effort to keep them together. Honda doesn't link them and if an engine has a quality problem that wasn't a minor adjustment, they would yank it and drop another in its place.

I think it maybe a screw up of a machine shop and their fix for this.
Got anyway to get a measurement of the ID of the brass inserts?
Curious if the ID is matching stock galley ID or if it is smaller or larger.

I have some metric and inch drill bits and some dowel pins I can use to measure. I would bet it’s close but not exact to the factory hole. I don’t have a spare case to measure but if someone else does that would be helpful.

[onepieceatatime]

I checked quickly before leaving for work today. The one photo is a number 17 drill bit, the other one is a number 12 drill bit. It appears to be a tapered hole. The 12 is tight at the top, the 17 drops in a ways better getting tight. I can try to check it out a bit more tomorrow if you need me too.

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[DaveBarbier]

I seriously doubt it is factory. If it were factory I think you would see exact match on engine and frame and they would do lots of effort to keep them together. Honda doesn't link them and if an engine has a quality problem that wasn't a minor adjustment, they would yank it and drop another in its place.

I think it maybe a screw up of a machine shop and their fix for this.
Got anyway to get a measurement of the ID of the brass inserts?
Curious if the ID is matching stock galley ID or if it is smaller or larger.

The holes are approximately 3/16”. They aren’t completely uniform in size down the hole. 3/16” only fits in part way and then 11/64” fits more and 5/32” fits all the way through. Definitely not factory. And I’d bet it’s not even a machine shop. It seems like backyard alteration. The holes aren’t perfectly straight. Might have been one with a screw gun.