Topic: Yet another 550 top end rebuild

[Retroben]

If anybody's been following my project thread, you'll know I just got a 1978 CB550K running for the first time in probably 20 years. The bike runs fantastic, I have yet to really put it through its paces (so far the carbs are just bench synched and I haven't even timed it, just set the point gap). I'm now going to rebuild the top end, because:

1. I'm blowing oily smoke and leaking oil all over the place, as in pools, not slow weeping.

2. I know from experience that anything made of rubber on these bikes needs replaced at this age.

3. I know the PO was inside the top end because of all the sloppy silicone goo all around the valve cover, hacked up screw heads and a broken ear next to the #2 exhaust valve tappet cover.  I can actually see oil bubbling around the valve cover through the valve cover gasket when the engine is running. I can see at least a couple of my tappet cover o-rings are leaking, but I can also see oil coming out from the sides of the head gasket area - the infamous oil passage o-rings.  There's also plenty of oil coming down the front of the engine, so I'm going to suspect the "pucks" too. In other words, there's so much that could be wrong, I need to open it up just to see what the heck's going on in there.

4. I broke a tap in one of the exhaust stud holes, trying to "clean up" the threads after a 1/2-turn crossthread bungle. I learned about how to use taps now. And I found out that you can dremel out a broken tap with a diamond-tip dremel bit in just three short hours, and still leave ALMOST enough thread to hold the stud in place. So I need to have a helicoil put in that hole, and I'm not going to try to do that in this garage without a drill press or even a vise.

Haven't done another compression test since before I got it running, but they were all within 10% of each other in the 140-150PSI range (dry) with an auto parts store compression tester.

I may opt to have the valves lapped and the exhaust stud fixed at a machine shop. I ordered the complete gasket kit already. I plan to try to avoid removing the cylinders, but I know that if I break the bottom gasket seal, I'm going to have to replace the bottom gasket too. I'll have it on hand anyway as it's part of the kit.

*sigh*

Looks good until you stop and the smoke starts from oil dripping on the header. And I feel like people are staring at my shiny shoes and pantlegs.

SocoMoto's video rocks, BTW. That's the kind of stuff that really helps me.

[Retroben]

Bought the full engine gasket kit and the pucks.
I disassembled down to the crankcase. Head and cylinders went to a machine shop. Valves lapped, new seals installed, head faced. Cylinder mating surfaces faced and cylinders deglazed.
Opted not to change rings. I inspected all of them and measured gaps, all well within tolerances.
Reassembled by the FSM, tightened head bolts according to prescribed sequence in three rounds  at ~5 ft/lb per round, up to 16 lbs.

Reassembled, went through the usual cam-chain learning curve. Started the bike, fired right up, no oil leaks, runs great!

Except now it seems like the head gasket is leaking in the area under the #4 carb inlet. Sudden acceleration gives a loud cracking-pop sound, and you can put your hand there and it feels like there's exhaust blowing out of the head gasket area when you twist the throttle.

Just out of curiosity I put a torque wrench on the exposed head nut there over cyl#4 - it was looser than 15 lbs.

Does this mean my head nuts came loose? Should I have used loctite on them?

I want to assume the machine shop did the job properly. They are a reputable family-owned business, and professionals.

Help and advice much appreciated.
Thanks
Ben

[mickwinf]

i just had the same problem on my rebuilt 500. ran great at first then started to spit just like yours, istarted to strip and found the nuts were loose. I took a risk and just retorqued them, seems to be ok now but haven't ridden much since.My theory is when i replaced the head it was not properly down, but after a few miles it settled down to its correct position hence loosening the headnuts.Hope it will last as it will save a stripdown.

[Mo]

When you torque the head down, in order of course, you should go back in the same order and verify the bolts are torqued correctly.

Sometimes as the head comes down, the bolts you just torqued become loose since the head isn't as far down as it can be.

[matt mattison]

When you torque the head down, in order of course, you should go back in the same order and verify the bolts are torqued correctly.

Sometimes as the head comes down, the bolts you just torqued become loose since the head isn't as far down as it can be.

+1. Never loc tite head fasteners . Did you replace the head studs, or use the old ones? It's a good idea to replace the head studs or bolts when disassembled. The reason why is that the fasteners actually stretch when torqued. The stretch is necessary to maintain torque value. Many used head fasteners over again, without a problem. I always "try" to replace mine with new. I might be wasting money, but I sleep better.

[dave500]

i pull those to 20 ft/pounds,a little higher than the book spec,dont torque those two odd one out little six mm bolts fore and aft on the head,just nip them down plus a little more with a short spanner.

[Retroben]

Thanks everybody!

I should mention that all the advice I got on this forum beforehand made the job a lot easier. From what I read, I knew the oil passage o-rings would be bad (the right side one was actually installed crooked and cut, looked like a snail when I pulled it out) and the pucks were all...dare I say it...embrittled too. (not my word, but a great word!) So when I opened up the top end I knew what to expect and that's always a big part of the game. So thanks to all the experts out there.

I did not replace my head studs. Must say the head nuts were torqued down gorilla tight when I removed them.  I broke each one loose in reverse of the tightening sequence, then had the head/valve job done and cylinders deglazed by the machine shop - the machinist said all mating surfaces were perfectly flat, no warpage.

I did torque all the head nuts down in three passes of 5 lbs each, with one extra pass at the end up to 16 ft/lbs. I guess I will go to 20 now (except the 6mm bolts), and see if that cures the present issue. 

Thanks again!

[Retroben]

Update.
No more leaky head gasket but oil is just all over the place, a real mess. Pucks replaced, oil passage o-rings carefully replaced, everything tightened to spec and in order. Where is it coming from? Dripping off the fins.

It seems to be coming from above but really collecting right around the head gasket. I'll start with the tappet port covers, and work my way down. But these are all new gaskets and o-rings. Why should they leak?

Should I name the ebay vendor who sold me the complete gasket kit?

[luap]

what gasket kit did you end up going with?
I havnt done it but I believe there is a Black light Dye you can put in the oil so see where the leak is coming from. Also heard if you put some flour  at the highest point of where you think its leaking the oil will bead in the flour

[Killer Canary]

Did you replace the four O-rings on the cam end covers? They piss like a race horse when they're bad.
You'll track it down soon.

[dave500]

dont forget the bracket bolt that holds the end caps,,throw the stock deformed alloy washers which are on it and get new copper washers for the top and bottom of the bolt,make sure the bracket has no burrs aswell,these leak from that hold down bolt.

[Retroben]

This is the kit I bought:
http://www.ebay.com/itm/New-Full-Engine-Gasket-Kit-Set-Honda-CB550-CB-550-CB-550-1974-1978-Four-F-K-/360507251986?pt=Motorcycles_Parts_Accessories&fits=Model%3ACB&vxp=mtr&hash=item53efe81d12
End cap o-rings replaced as part of the gasket kit.
Will doublecheck the crush washers under the end cap brackets - those were less than perfect now that I recall.

[dave500]

they need one under the bolt head and one under the actual bracket.