Topic: 79 CB650 The Mayor - Revive and Freshen Up

[DaveBarbier]

Working on cleaning up the head and cylinders. I’m going to drop out the barrels to clean the gasket surface. I feel I won’t need to get it machined after. But if I do, eh.

But first I needed to remove 3 really stuck head bolt washers. 9 fell out after shocking them with a punch but three wouldn’t go. I know this looks scary but it works. You can use a screw gun too but the drill press offers much more downward force. Line up the holes, and slow down your drill press as slow as it’ll go (I have a slow speed attachment so I can get it to like ~100rpm). Hover the bit right above the washer and then in a quick motion hit the washers with some moderate pressure. It’ll bite down into the washer and break it free. Works like a charm.

[grcamna2]

A type of 'Press' using a large drill bit

[DaveBarbier]

A type of 'Press' using a large drill bit

Exactly. But the machine is on so you’re still cutting a bit. At least the amount of that little chip you see. Only now I need to get more washers and they’re not a standard metric size.

[scunny]

They are a pain to remove, I just used a long metal rod to tap them around a bit, they came loose in the end.

[DaveBarbier]

Removed the barrels. In the toaster oven at 350°F took it out with my welding gloves and popped out the barrels. The base gasket started to almost flake off too which was awesome. Just have to put this and the head in the parts washer and I’ll blast the carbon deposits from the exhaust ports, combustion chambers and pistons with crushed walnuts.

[DaveBarbier]

More progress. Blasted the carbon deposits with crushed walnuts and it’s looking a lot better. Not perfect, but much better. And yes, the fins and overall casting I didn’t touch as far as cleaning. Don’t care if it’s really clean.








Then, after cleaning all gasket surfaces I put back the barrels in the cylinder block. Heated up the block to ~200°F and put the barrels in the freezer. I slid them in and they didn’t go in all the way. I think the temperature difference wasn’t enough. I put the whole thing back in the oven @ 350° and then pushed them in with welding gloves. They sat flush against the head gasket surface and I let it cool. Then after it was cooI, I noticed that the barrels weren’t sitting completely flush anymore. They were all about .0025” proud. I made a few clamping fixtures to keep pressure on them and then back in the oven. After about 30 minutes I took them out, let them cool and now all good. Completely flush. The previous cooling at different rates must make the barrels tend to push out of their holes a bit. The angle iron is pushing on some aluminum bars so it only pushes on the barrels. Easy peasy.





Lastly, when cleaning up the case gasket surface I see what looks like gouging from the cam chain. You can see some aluminum being disrupted into the gasket surface. I filed that down and it’s as good as new.

Next on the list is valve lapping and reassembly! Might fire it up this coming weekend.

[grcamna2]

Those walnut shells are good to remove the carbon w/o etching the metal,not bad.I like how you did the clamps to keep the pressure 'on' in the oven.You going to have those barrels precision honed then new rings ?

[DaveBarbier]

You going to have those barrels precision honed then new rings ?

Nope! Just doing only necessary things to get it going and running well. No honing and same rings.

[grcamna2]

You going to have those barrels precision honed then new rings ?

Nope! Just doing only necessary things to get it going and running well. No honing and same rings.

The Mayor engine may burn a little oil.

[RAFster122s]

With the metal used in the fins not being particularly stable an align bore is recommended by HondaMan to re-establish about 5-7% loss of power that the initial heat shifting of the metal allows. The align bore re-establishes that alignment increasing efficiency and it maintains it, per Mark. As long as you don't overbore dramatically causing the liners to become thin.

I have always been cautious thinking liners aren't perfectly round and therefore wouldn't be good to pull and reinsert without a bore tp ensure they were/are aligned. But, that isn't based on fact, merely my theory. You definitely need to ensure the liners are properly seated. I have a cylinder that had new liners installed and they didn't press them in place properly and after overboring for a 592cc kit a liner dropped after/during break-in causing that expensive overbore job be wasted, as it required another rebuild/starting over.

Surprised you don't want to clean it up and repaint it while you have it torn down...even if you are not rebuilding the motor.

I hope you are successful in the clean up and reassembly.

[onepieceatatime]

I do not plan to clean up (much) or repaint the engines that I am working on either. I personally do not care to have a vintage bike that looks like it is fresh off the assembly line.

[DaveBarbier]

Surprised you don't want to clean it up and repaint it while you have it torn down...even if you are not rebuilding the motor.

I hope you are successful in the clean up and reassembly.

Thanks David, but no way am I putting much effort into this thing. The grime is staying and it won’t ever see new paint.

[DaveBarbier]

You going to have those barrels precision honed then new rings ?

Nope! Just doing only necessary things to get it going and running well. No honing and same rings.

The Mayor engine may burn a little oil.

A hone and re-ring isn’t required for a top end job. The rings are already mated with the cylinders. The reason to hone and re-ring is to get the motor to the point where it is right now. Worn in and mated to it’s particular bore.

[jgger]

Dave I know you put the sleeves back into the same holes they came out of. But did you clock them to their original positions?  I'm watching to see how this goes, very interesting.

[DaveBarbier]

Dave I know you put the sleeves back into the same holes they came out of. But did you clock them to their original positions?  I'm watching to see how this goes, very interesting.

Yes I did. That’s what the little pink witness marks are for. But having taken apart engines the rings spin around so they don’t always end up where you put them in the beginning anyway so not sure it was really necessary to clock them exactly how they were before.

[jgger]

I would think that when the motor is running the force of the piston to the bore is front and back because of the crank rotating, it's not a straight up and down.  Same reason the piston has a skirt on the front and back and not the sides. The bore probably wears oval because of this. I think it was wise to clock them.

[DaveBarbier]

I would think that when the motor is running the force of the piston to the bore is front and back because of the crank rotating, it's not a straight up and down.  Same reason the piston has a skirt on the front and back and not the sides. The bore probably wears oval because of this. I think it was wise to clock them.

Yeah, I can see that. If I remember I’ll measure them with my dial bore gauge.

[DaveBarbier]

Installed the cylinders this evening. Pretty uneventful which was nice.

Also used my endoscope to make sure the tensioner is seated in the little pocket in the lower case. Kind of hard to see but it definitely seems like it’s good.

I did forget to measure the cylinder bores to see how out of round they are but I can still do it. Maybe tomorrow. Next step is lapping the valves.

[grcamna2]

Dave,will you keep those two brass sleeves in where they were around the two oil restrictors ?

[DaveBarbier]

Dave,will you keep those two brass sleeves in where they were around the two oil restrictors ?

Yes, I’m not going to mess with them. Bike was getting good oiling to the top end when I first fired it up so whatever the reason is they did that it’s working just fine. Besides, not much I could do. I’d have to drill and ream the holes and then reinstall sleeves of my own. Makes no sense.

[DaveBarbier]

Lapped the valves and installed the springs and all valve train. I’m actually surprised the valves and seats look as good as they do. They seemed really pitted but they lapped up really well. The picture of the valve is the worst one, all others are almost totally clean. Making progress.

[RAFster122s]

What's the story on the plug hole having a sawtooth edge

[DaveBarbier]

What's the story on the plug hole having a sawtooth edge

The later 650’s aren’t like that. I just assume Honda didn’t bother finishing the machine work on those. The 650 has a more hemispherical head than the other SOHC4’s so the plug hole threads exit with a pretty aggressive toothed pattern.

Here’s a picture of my ‘82 head from MRieck.

[SOHC4 Cafe Racer Fan]

This was mine BEFORE Mike's work -- see the thread pattern:

image_zpsf7zzltsb by Donald Leonhardt, on Flickr

[DaveBarbier]

This was mine BEFORE Mike's work -- see the thread pattern:

image_zpsf7zzltsb by Donald Leonhardt, on Flickr

Ah interesting, I see a similar saw tooth pattern. I didn’t even think Mike may have worked on the combustion chamber.