Topic: Cb550 top end rebuild and engine condition question

[Jimsun]

Ive bought a cb550 spare engine and im wondering if its worth rebuilding. Ill be posting pictures of marks i do not see from my engine or my friends.

Heres the first one from the oil filter.
Note the lines on the surface

[mickwinf]

normal casting marks

[Jimsun]

I also noticed this. It seems like im missing a bracket. Any idea where i can get it?

[Jimsun]

Also is there a way to remove the top head gasket without prying it out? Is prying is the only way.

See pic. There seem to be 2 pins that holds it to the cylinder head.

Im trying to knock it free with a mallet but no cigar.

[Jimsun]

Cam lobes and rockers

[dave500]

the bracket you need for that end cover are left and right,they are marked L and R,those alignment dowels are steel and expanded rust will have wedged them in the valve cover,soak them with crc/wd40 or what ever and with light levering and perhaps light punching down on the steel pins itll come free,try to lift it off squarely though.

[Jimsun]

the bracket you need for that end cover are left and right,they are marked L and R,

The bike didn't come with them. Is there a place to source them?

those alignment dowels are steel and expanded rust will have wedged them in the valve cover,soak them with crc/wd40 or what ever and with light levering and perhaps light punching down on the steel pins itll come free,try to lift it off squarely though.

I ended up using a mallet to free the head cover off. Im trying to use less prying as i dont want to dmg the surface.

[P.abrera]

Not more than a newb here, but what worked for me was a generous application of heat from a heat gun. Softens the bond of old gaskets (and sealant if used) and since aluminum expands at a greater rate than steel, it should in theory, allow more wiggle room for those dowels.


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[Jimsun]

Does anyone h e any input about the camshaft lobes?

[Duanob]

Depends on what your plans are. If you're going to spend butt loads of money on this bike like some guys then you will want a new cam. If you just want to put it on the road at minimal cost then it's good enough. It won't cause any issues for a while but it won't last forever either.

[TwoTired]

The cam lobe and rocker wear patterns (non-ideal) are indicative of rocker shaft hole elongation and abnormal wear.

Look for a 77-78 Rocker cover and try the to get the cam and rockers from the same engine.

[Jimsun]

I manage to separate the whole top end and ive got a head cover as well as a camshaft from a 77-78.

Im looking at the gaskets from the cylinder and the head. What would be the best way to clean them? Would machine shop be okay taking it to resurface even with the sleeves stocking out?

[Jimsun]

Take the head and jugs to the shop. They'll peel the gaskets so they can surface the mating surfaces. The sleeves sticking below the cylinders is not an issue or unt they want to machine the lower surface to the crankcase. In that case, the shop will remove the sleeves.

But understand, milling those surfaces is generally not required. Only to correct warpage or irregularities. If none exists, then scrapers, gasket solvents, acetone and beer are needed to remove the old gaskets.

I see. I thought its always a good idea to get the mating surfaces cleaned so it wont leak on yea later on.

[davesee]

i would just peel the gasket away, using some solvents and gentle use of an old screwdriver. gasket remover will aid with the removal of any gick left over. don't nick or scratch the mating surfaces. time, patience and solvent are all that are required.

if you're going to clean and polish the engine and replace all the seals, then i agree with twotired...try and source a new head and cam, as those lobes look rough. if they cause problems even a year down the road, you will have to redo all your work, and then some.

similarly, it seems worthwhile to me to have a machinist measure the cylinder bores to ensure they're in spec...again, all the work will have been for nothing if they are no longer round. i would not have anything resurfaced at the machinist unless some warpage needs to be corrected.

what do those cyclinders look like inside?

[Jimsun]

Ill post pics of the inside today i was in a rush yesterday. As the walls seemed cleaned. All even surface all around. Ill post a pic in 10 mins

Pleade note the first 2 pics are like burnt marks(?) or something on the wall. Is that okay to leave or should i get the walls honed as im sure itll get rid of the marks.

The 3rd and 4th pic are the walls it seems even with no nicks or scratch showing.

5th and 6th are the head cyl. Please look at the marked exhaust valves. Why are they like that?

Lastly is there a chemical u guys would advice that i can use to clean the head cyl?

[Jimsun]

It seems like all 4 have some marks on them. I sprayed sone gasket removal spray and the heads cleaning up good. Im using a plastic blade to remove the gaskets.

Ill get the walls measured and honed.

[Vinhead1957]

The engine was burning oil!  Those heavy carbon deposits are left from oil consumption.  Now why ?  The cylinder wall damage looks like it was caused by rusting during a long period of not running.  The rings could not really seal on an uneven surface letting oil into the combustion chamber. Personally, I would be looking at a redo of the complete top end. Not hone but bore to the next size. New pistons rings  and complete valve job.  You got her down to bones. Why not do it right.

[Jimsun]

The engine was burning oil!  Those heavy carbon deposits are left from oil consumption.  Now why ?  The cylinder wall damage looks like it was caused by rusting during a long period of not running.  The rings could not really seal on an uneven surface letting oil into the combustion chamber. Personally, I would be looking at a redo of the complete top end. Not hone but bore to the next size. New pistons rings  and complete valve job.  You got her down to bones. Why not do it right.

I see. Can i still use the rings i bought for the engine if i bore it?

[Vinhead1957]

 Not unless they are for oversized pistons

[davesee]

Ive bought a cb550 spare engine and im wondering if its worth rebuilding.

if the cylinders need reboring and you need oversize pistons, i think you have your answer.

[Jimsun]

Ive bought a cb550 spare engine and im wondering if its worth rebuilding.

if the cylinders need reboring and you need oversize pistons, i think you have your answer.

so there is a chance or should i just get 650 pistons and rings...

[Jimsun]

Take your jugs and head to a competent machine shop and have them determine what actual machine work is needed. Then make your decisions when you know what you "have" to buy.

should i bring the shop manual along with my pistons?

[Jimsun]

When doing a top end, Do i need to replace "91301-200-000 - O-Ring 10 x 1.6mm - x8" which goes to the valve guide intake/exhaust if they are good?

[dave500]

you only replace those valve guide o rings if the guides are being replaced,replace the valve guide seals though.

[Jimsun]

I brought the head, jug and piston to gord bush for a quick look. He looked at the wall marks and he said it's nothing to worry about it's not oil burning. He also fitted the pistons to the jugs and said i'll not be needing any boring but he'll call me if there's any surprises.

The job will take approx 1 week. He will go further to inspect the head and pressure test for leaks. The cost is $330 CAD (not sure if it's a rip off) to have the piston, jugs and head ready to be bolted on..

He's apparently well known and have been in the business for a very long time.
http://www.gordbushperformance.com/index.html