Topic: Snugging up head bolts on old cb550

[Turbogrimace]

I just finished restoring a 78 550 but only replaced the cover gaskets. The head gasket is leaking a bit of oil only on the sides and the left side bubbled for a bit. Could I get away with retorquing the head bolts for a little while or will that just cause more trouble? Also could I just snug up the outer bolts since it's only leaking on the left and right side? I'd torque them to the 16 ft lb max listed.

[calj737]

If yu do that, I'd suggest you release all of them in reverse sequence, then torque them back to their stated max in 2 stages. First a full sequence at 10#, then a second sequence at 16#. That way you get a complete and even torque on the head.

[alacrity]

Try it, one at a time, from the center out. (you don't want one of the EDGE studs carrying more pressure than the center ones - follow the same pattern as in the shop manual - which does it this way for a reason).

Crack it open, torque it down. Do the next one, and so on, then back to the first one - guess what? It's looser than the last one you did (probably), give it another nudge.

AND most likely, you will still have an oil leak. It's because the o-ring failed at the edge of the block that always fails on these bikes after a time.

The fix as I posted elsewhere is a CycleX MLS head gasket installed after surfacing the cylinder block and head faces so they are perfectly flat.

It won't leak after that

[Turbogrimace]

Thanks for the info. The engine only has 17k on it, but 28 years of sitting isn't good.

[bochnak]

If you do decide to to a head gasket, do the base, pucks, and all orings as well. I have a top end video on this, see my sig.

[Turbogrimace]

thanks for all the advice.  I may still do a gasket later on.  I know there are some other leaks coming. 

All of the studs were surprisingly loose.  It took less than 8 ft lbs to loosen every single one of them.  The outer studs were almost just hand-tight.  This engine has never been touched since it was built in the factory and only has 17k on it. My uncle watched the bike get put together out of the crate in '78. 

I loosened and torqued each one individually to 16ish ft-lbs.  After one pass, I went over them again, but they were all set.   

After putting some yamabond back on the sealing pucks and letting the engine sit for a few hours, I warmed the engine at idle for about 20 minutes and let the rpm's creep up.  I inspected it for any oil leaks once it was hot and had run at 4k for a couple minutes.  Didnt see anything new, but beforehand, it needed a little loading to really start to seep.  After a bit of a ride, there was some oil puddling on the fin just below the head, but it wasnt much.  A 5 mile spin with varying loads led to a little more oil, but nowhere near as much as before.  It leads me to wonder if what's coming out now is just some residual oil-soak pushing out of the gasket.  There are no more bubbles emanating from the left side of the gasket and the engine even seemed to idle more smoothly. 

Storms started rolling through so I had to cut my testing short.   Hopefully this will do for now.  I'm going to get some stove rope to have on hand just in case i need to pack the fins.

[calj737]

You procedure for torquing the head (if as you posted it) is completely wrong.

You need to release the head nuts in reverse order from tightening them. Then, tighten the studs in sequence, preferably in half torque. If you released a stud, then re-tightened that one, then repeated this through all of them, I am not surprised there's little improvement. You may not solve the leak with a re-torque, but as you discovered, they surely needed to be done!

[Turbogrimace]

Interesting. I followed the procedures for Saab heads.

[calj737]

Interesting. I followed the procedures for Saab heads.

Are you riding a Saab or an SOHC?

Its always been a standard practice on motors that I've seen and dealt with to sequence torque head studs, and to release them in reverse. You might undo them in reverse and try again to see if the outcome is any different. It may not be, but I assure you, sequence torque avoids warping heads.

[przjohn]

Interesting. I followed the procedures for Saab heads.

Are you riding a Saab or an SOHC?

LOL, that one made my morning.

[slikwilli420]

Im with Cal. I have not done near as much motor work as many here, but anything I have ever read suggests loosening in the reverse sequence of torquing. Additionally, this may be an opportunity to get yourself a factory manual and a Clymer for your machine.

[Jonesy]

The oil feed galleries are on the outside edges of the cylinders on the CB550 and as already pointed out, they are sealed with O-rings which harden and don't seal after years of baking in that hot environment. Retorquing the head probably won't help. My wife used to get oil stains on her jeans after riding her 550 as drops of oil would ooze out and blow off the head in the wind. After replacing all the gaskets and seals the engine was oiltight.

At least you can reseal the top end of the 550's engine with it still in the frame, unlike it's bigger brother. 

[Turbogrimace]

Interesting. I followed the procedures for Saab heads.

Are you riding a Saab or an SOHC?

Its always been a standard practice on motors that I've seen and dealt with to sequence torque head studs, and to release them in reverse. You might undo them in reverse and try again to see if the outcome is any different. It may not be, but I assure you, sequence torque avoids warping heads.

I have a manual for it and re-torqued in the appropriate sequence.  The only thing I didn't do is loosen the entire head in reverse sequence.  Being that the studs were probably close to the same torque originally, re-torqueing in sequence seems the same as applying half torque once through, then going back over them for full torque.  I loosened each one before-hand to make sure that the threads were clean.

I'm glad I'm not riding a Saab, but due to the lack of any official procedure for a CB550 head, using another manufacturer's re-torqueing procedure for a 4 cylinder head seems logical to me.  Especially a procedure that's quite often successful.  It also agrees with what Alacrity mentioned.... and I forgot what you had mentioned reversing the entire pattern first when I went out to the shop .

I'm fighting a losing battle, but I'm incredibly happy that it's a 550 and not a 750.  I'd hate to have to pull the engine to redo the gaskets.  Been there and don't want to go back.  My goal in re-torqueing is to just get a few weeks out of it for a trip to North Carolina.  After that, I'm going to tear it down, decarb, and seal it up.  The gasket stopped bubbling and the oil loss is a lot less.  that's good enough for now.

[Turbogrimace]

A quick update.  After a 40 mile spin through some country roads and highway, there was only a hint of oil on the fins.  Not even enough to bother wiping off.  Hopefully this holds for a few weeks.

Thanks again for the help Cal and Alacrity. 

I was talking with a coworker and it turns out that the Saab procedure is similar to a mil spec for resetting the torque on other engines.  I'm glad it worked out and happy to see there's several answers to the problem. 

[calj737]

Ah, Mil Spec. Tolerances just tight enough to function.  Happy you're better off.

[Turbogrimace]

Ah, Mil Spec. Tolerances just tight enough to function.  Happy you're better off.

Precisely.  I deal with it every day.  Those two abbreviated words make everything cost 10x more.

[flatlander]

do yourself a favour and download the honda shop manual, it's free and you can print it out and keep it next to you while working on the bike: http://www.honda4fun.com/materiale-documentazione-tecnica/shop-manual

for your bike, i think that's a better authority than saab or mil spec.

[Turbogrimace]

I will use the shop manual that I've had for many years when the information I need is within it's binding.  But thanks for the tip.

[Duanob]

The oil feed galleries are on the outside edges of the cylinders on the CB550 and as already pointed out, they are sealed with O-rings which harden and don't seal after years of baking in that hot environment. Retorquing the head probably won't help. My wife used to get oil stains on her jeans after riding her 550 as drops of oil would ooze out and blow off the head in the wind. After replacing all the gaskets and seals the engine was oiltight.

At least you can reseal the top end of the 550's engine with it still in the frame, unlike it's bigger brother. 

I'm with Jonesy on this one. The o-rings might seat for a little while but I think they will start leaking again. You might get lucky for a little while but those original o-rings are hard and brittle.

[Turbogrimace]

It's good enough for now, but I cant tolerate an oil leak on a honda. If I get a summer out of it, I'll be giddy. Nothing like a nice top end rebuild in the breezes of a cool fall day.

[Turbogrimace]

A little update.  After tightening down the head bolts, the head wept a little more and then stopped.  I haven't had any head leak for about 1000 miles now.  I followed the original torque pattern, loosened the nut free, then torqued back to spec.  Then went over them again in the same sequence to verify.  Since I couldn't find anything specific to a CB, I followed the Saab and mil-spec procedure with success. 

Some of the oil leakage might have been from shrunk gaskets.  Once they got some hot oil on them for a while, they swelled back up and got back to work.... maybe.