Topic: CB500 top end work

[dazemc]

'71 CB500,

I was burning oil out of my right side exhaust (4-2) and was having some abnormal noises, caused by misfires from 3 and/or 4. When I originally purchased the motorcycle it was not running on cylinder 3. The spark plug appeared to be plugged in but was loose from the boot. I have assumed the oil burning was from the rings being stuck on this cylinder or oil deposits burning off. I've put about 800 miles on and oil consumption has been going up and the idle is getting worse, along with oil seeping out between both sides of the head. Spark plugs 1-2-4 are all oil fouled. #3 spark plug was actually pretty good, all nice and tan. Compression shows 125/1 100/2 124/3 125/4. Someone correct me if I'm wrong, but they are all on the low side of spec? The head bolts did feel a little loose when breaking them free. Nobody will be surprised about cylinder 2 being low if you remember me posting about my left cam cover coming off and pushing the rocker shaft out.

Anyways that brings me to where I am now. I've never done any kind of work like this and I want to do it as right as I can within a reasonable monetary value, I'm broke! Basically I'm trying to do a rebuild to get me to my next rebuild. I have the head and barrel off along with all the pistons. Bought a spring compressor and took out all my valves. Cylinder 2 intake valve is definitely bent near the tappet side so I'm waiting on a new one. The biggest surprise so far has been finding out that whoever worked on this last didn't think the valve stem seals were necessary for cylinder 4. This would explain the burning oil despite okay-ish compression! I already ordered rings anyways because that's what I thought was wrong.... I plan on replacing them all. They also didn't think any of the exhaust crush washers were important either. This makes me worried that there has been other things missed. I'm in the process of cleaning everything up and I don't want to miss anything. I'm following that pinned leak free top end rebuild but I have found some conflicting information about using sealants. Seeing how it's been some time since that was made, I figure there may be some new tips I can find. I was just going to use hondabond on the pucks and install everything else dry. Is this the right way to go? What's the best way to make sure these oil passages are clear? Anything that I can check on the bottom end without tearing into it more? Can I reuse these retaining clips for the pistons? What all should I be checking while I'm in here? I've been using the blown out diagrams on cmsnl to try and Identify the parts that I either don't know or I am missing. I'm just worried I'm missing something especially with those missing valve stem seals, oh and especially since I've never done this before. I am lapping the valves too by the way.

Cylinder 4 valves were awful!

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[bryanj]

NO YOU CAN NOT RE USE CIRCLIPS thats for a start, check carefully the guide on the bent valve, any cracking means its duff. No sealant anywhere.
Check the restrictors in the base gasket dowels and make sur they go in the correct way up the before fitting cam cover but with cam and sprocket fitted turn engine over a lot to make sure oil gets to the cam

[MRieck]

NO YOU CAN NOT RE USE CIRCLIPS thats for a start, check carefully the guide on the bent valve, any cracking means its duff. No sealant anywhere.
Check the restrictors in the base gasket dowels and make sur they go in the correct way up the before fitting cam cover but with cam and sprocket fitted turn engine over a lot to make sure oil gets to the cam

Wow Bryan....that bike is 50 years old. I crack up when I see your 500 frame #....my 2000 RC-51 is #33. It's a keeper like yours.

[bryanj]

Mike, just got my borring bar rewired to do the big liners and pistons to transfer that gorgeous head you did for me to, that with the webcam 58a cam is gona be some sort of sleeper.
Hope you keeping well mate
Bryan

[dazemc]

NO YOU CAN NOT RE USE CIRCLIPS thats for a start, check carefully the guide on the bent valve, any cracking means its duff. No sealant anywhere.
Check the restrictors in the base gasket dowels and make sur they go in the correct way up the before fitting cam cover but with cam and sprocket fitted turn engine over a lot to make sure oil gets to the cam

Okay I'll get some new circlips too, can I find those at a local shop or is that something I'll have to order? I bent the hell out of the one of the two dowels on the upper end so I ordered two of those because I don't see the point in even attempting to bend mine back into place. I don't plan on using sealants then, I'd much rather have a little bit of weeping than a blocked oil passage. Should I use thread lock on the two bolts holding the cam socket? I thought I remembered someone saying something about that.
Unfortunately I have about a week or two of waiting on parts/tools but that also means I can take my time. The guide doesn't appear to have any cracks and other valves were able to slide in and out.

Is a little side play okay on the connecting rods?


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[Maraakate]

Piston circlips are still available from Honda.  Partzilla lists them at $0.88, but I bet you could call your local Honda dealer and give them the part number and get it cheaper than what it would cost to include shipping via Partzilla.

[jonda500]

I use locktite on all internal bolts?
John

[dazemc]

I use locktite on all internal bolts?
John

Yeah I've read enough posts about rogue knock bolts destroying the top end for me to not at least use some on those. Gonna go with the toothpick application method.

Piston circlips are still available from Honda.  Partzilla lists them at $0.88, but I bet you could call your local Honda dealer and give them the part number and get it cheaper than what it would cost to include shipping via Partzilla.

I've never really been inside a dealership to be honest. I'll have to call but I doubt they'll be more expensive than shipping costs.


Any tips on cleaning out the grooves for the rings on the pistons?

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[jonda500]

I use an old broken piston ring to gently scrape the carbon out of the grooves
John

[dazemc]

That's not a bad idea. I really wish I could afford some brushes for my Dremel right about now.

I broke two of the old rings when I was taking them off. I think after I get these cleaned up I'm going to use the old rings as practice so I hopefully don't break the new ones.

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[dazemc]

Any negative effects if I leave some parts submerged in acetone for a few days?

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[Kenzo1979]

Any negative effects if I leave some parts submerged in acetone for a few days?

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Not sure about acetone, but the manual says to use a paraffin for cleaning. When I rebuilt my 500 engine, I used mineral spirits.


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[Maraakate]

Piston circlips are still available from Honda.  Partzilla lists them at $0.88, but I bet you could call your local Honda dealer and give them the part number and get it cheaper than what it would cost to include shipping via Partzilla.

I've never really been inside a dealership to be honest. I'll have to call but I doubt they'll be more expensive than shipping costs.

I've been finding out that any OEM part that is still available via Partzilla my Honda Dealership can order it and it's almost always within a dollar or two of the Partzilla price.  Usually the same price or cheaper.  I've found it's only worth ordering from Partzilla if I have to put a large order in.  But when you need an o-ring here, a seal there, etc. it doesn't make much sense to pay $7 in shipping costs from Partzilla for a $2 part when the dealership can sell it to you for $2.05 or whatever and you can just pick it up in a day or two.