Topic: 77 CB550F motor apart. Some questions.

[GardenGnome]

Hello. So I have taken the plunge and decided to take the motor apart and rebuild the top end. There was a gasket leaking a little oil, and well now I'm left wondering what the best method is for getting the I believe it's carbon build up off of the top of the piston. I tried a nylon brush and some carb cleaner, but that proved to be ineffective (granted I didn't let the piston soak in the carb cleaner that might have been my error). My question is what methods have you used that have been effective for removing and cleaning the carbon crust build up on your pistons. Last question regarding the pistons, as a novice in doing anything with an engine, is there a way to tell that the piston rings need to be replaced? Or is it just generally good practice that if you're going this far you may as well go the extra step and put new piston rings on?



Also, the engine bolts in the picture below have a bit of rust on them. Is this anything to be concerned about? would it be ok to take some high grit sandpaper and lightly sand the rust off? Thank you for looking and giving any advice you can.

[FunJimmy]

I'm of the opinion that rings should always be replaced and fresh cross hatch to cylinders when pulling apart the top end. Especially on an old engine. As for the surface rust on studs...don't sweat it. You'll never see it when rassembled.

[BomberMann650]

You can chip away most of the carbon buildup from the pistons with a chisel.
Then dunk em in berrymans chem dip at half hour increments until clean.

[GardenGnome]

You can chip away most of the carbon buildup from the pistons with a chisel.
Then dunk em in berrymans chem dip at half hour increments until clean.

I assume that taking precaution with a chisel on the piston head is best practice. Not going too aggressive. Would a brass brush be a better tool? I am just afraid to scratch the top of the piston head.

[GardenGnome]

I'm of the opinion that rings should always be replaced and fresh cross hatch to cylinders when pulling apart the top end. Especially on an old engine. As for the surface rust on studs...don't sweat it. You'll never see it when rassembled.

Ok good to know. I did end up purchasing a thing to make fresh cross hatches on the inside of the piston walls as well as new rings. In your opinion, is a  piston ring compression tool necessary for the installation of the new rings? I've been told and read that you do not under any circumstances want to scratch the piston. If a piston ring compression tool is not needed, what method works best for installing new rings without causing harm to the piston?

[TwoTired]

I would only replace the rings if there were scoring to remove from the pistons/cylinder.  Or if there was an issue with a compression test.  have you measured the cylinders for taper and out of round?  How much ridge was at the top of the bore?

Honing removes metal, taking you another step closer to a cylinder bore job.  Same as the now necessary break in period with the new rings, scratching off the cross hatch to seat the new rings.

If you have a broken ring, you have no choice, of course.

The bottom of the cylinders have a taper/ramp for helping to guide the rings. Cleaning/smoothing that helps a bit.  Still need to compress rings carefully and guide them onto the cylinder walls.  It can be done with your finger nails,  But, it is more tedious than ring compressors.  Two pistons go in at the same time.  Some use band clamps from the hardware store.

Did you take the cylinders and pistons off for a reason, other than to just look at it?  Can you put everything back in in the same positions you took them out of?  The parts all "marry" together.  Mixing them up restarts a break in process.

Oven cleaner works well on carbon.  But, it will etch aluminum, as it is lye.  You can still use it if you only apply it to the carbon deposits and remove the lye just as soon as it does it's job.

Cheers,

[GardenGnome]

I would only replace the rings if there were scoring to remove from the pistons/cylinder.  Or if there was an issue with a compression test.  have you measured the cylinders for taper and out of round?  How much ridge was at the top of the bore?

Honing removes metal, taking you another step closer to a cylinder bore job.  Same as the now necessary break in period with the new rings, scratching off the cross hatch to seat the new rings.

If you have a broken ring, you have no choice, of course.

The bottom of the cylinders have a taper/ramp for helping to guide the rings. Cleaning/smoothing that helps a bit.  Still need to compress rings carefully and guide them onto the cylinder walls.  It can be done with your finger nails,  But, it is more tedious than ring compressors.  Two pistons go in at the same time.  Some use band clamps from the hardware store.

Did you take the cylinders and pistons off for a reason, other than to just look at it?  Can you put everything back in in the same positions you took them out of?  The parts all "marry" together.  Mixing them up restarts a break in process.

Oven cleaner works well on carbon.  But, it will etch aluminum, as it is lye.  You can still use it if you only apply it to the carbon deposits and remove the lye just as soon as it does it's job.

Cheers,

I took the pistons off because I had the mind set of "well since I'm going this far..." I have already purchased new rings, but in all honesty I cant see anything wrong with the ones that are on there currently.  Granted I do not have any previous engine rebuild skills prior to this so for all I know I do need to replace them, however it is interesting to me to see the inner workings of a motor. I do have everything labeled and I do remember the order that things were removed. I feel like in my case it's best to be safe than sorry and order a piston ring compressor tool.

I've watch videos on putting on new rings and all of them the individual put the rings on starting from the top. What you're saying is that is should be from the bottom due to this slight taper?

Lastly, I have not measured the cylinders or the bore. what numbers should I be looking for, a tolerance if you will?

[BomberMann650]

You'll need new circlips to hold the wrist pins.  They're cheap. 

A brass brush won't begin to chip away the carbon build up.
Do be careful as you go about manually removing the crud.
Light taps, working across the surface, not down into it.
Its like artwork.  But it will help you in the long run.  Especially if you do get the berrymans chem dip.  That stuff really cleans parts nicely.  (Even if its not the same as it was in the glory days) putting in a pre-cleaned part will only get better results and a longer lasting chem solution.

[GardenGnome]

You'll need new circlips to hold the wrist pins.  They're cheap. 

A brass brush won't begin to chip away the carbon build up.
Do be careful as you go about manually removing the crud.
Light taps, working across the surface, not down into it.
Its like artwork.  But it will help you in the long run.  Especially if you do get the berrymans chem dip.  That stuff really cleans parts nicely.  (Even if its not the same as it was in the glory days) putting in a pre-cleaned part will only get better results and a longer lasting chem solution.

I'm so leery on trying to clean the top of the pistons. I guess I'll just have to dive into it with caution. Quick question BomberMann650, are the circlips something I can buy at a local hardware store? 

[Jimray23]

A cup type wire brush on a drill works good on carbon. Don't beat on your pistons!!! I agree, replace the rings while your at it. Clean the head studs to make sure their not to bad. If their pitted, replace them. Its better than breaking one under load and they are not that expensive in the grand scheme of things.

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Jim
I really don't see why people ask for advice if their not going to take the advice given.

[TwoTired]

I took the pistons off because I had the mind set of "well since I'm going this far..." I have already purchased new rings, but in all honesty I cant see anything wrong with the ones that are on there currently. 

I'm a "If it ain't broke, don't fix it" kind of guy.  All it takes is one mistake, and now its broke.  First hand experience can be expensive.   

I've watch videos on putting on new rings and all of them the individual put the rings on starting from the top. What you're saying is that is should be from the bottom due to this slight taper?

No.  I was talking about inserting the pistons into the cylinder sleeves.

Lastly, I have not measured the cylinders or the bore. what numbers should I be looking for, a tolerance if you will?

If you are taking a motor apart, you should have the Honda shop manual. 
Chapter 13 has a page for CB550 Service data that lists the dimensions and wear limits.  You have internal and external micrometers?

Cheers,

[GardenGnome]

I do have both of those micrometers. I'll reference the manual on here as ,y bike at time of purchase did not come with one. Thank you for your replies.

[GardenGnome]

I'll be the first  to admit that I just don't know what I'm doing; however, I am trying to take the proper steps by watching and reading. My goal as with any uncharted territory is to not screw this up. What's the worst thing that I could do. What mistakes are easily avoided when taking on this part of the rebuild with a motor? I'm genuinely curious, like what has worked for you and what hasn't? What could I do, read, or watch to better inform myself?

[BomberMann650]

You'll wanna get the circlips oem from honda.  www.hondabike.com offers a discount on self service ordering. 

A high rpm wirebrush will take the carbon off like Jimray said.  Just wear a dust mask if you do that.

[GardenGnome]

You'll wanna get the circlips oem from honda.  www.hondabike.com offers a discount on self service ordering. 

A high rpm wirebrush will take the carbon off like Jimray said.  Just wear a dust mask if you do that.

Thank you for the link and advice.

[bochnak]

Soda blasting does an excellent job for removing carbon:

https://www.howtomotorcyclerepair.com/images/cb500-cb550-carbon-piston-valve-after.jpg

[Keith]

Oven cleaner will soften the carbon buildup you can neutralize it with vinegar, then clean with detergent and water. Pay attention to carbon buildup in the ring lands (grooves) make sure holes which supply oil to the rings are not plugged, taking care not to damage the grooves. Check wrist pins for any play. Personally, I would split the case, and examine the bearings, crank, primary chains. Just my opinion, but I would install pistons from the top, the piston skirt helps align the piston in the bore, and one piston at a time can be installed. More time involved, but a more thorough job. Remember..there is never enough time to do it right, but there is always enough time to do it over.

[jonda500]

I suppose it's possible, but I have never heard of anyone installing sohc4 pistons from the top? Like TwoTired said the bottom of the cylinders has a little taper to help guide the pistons/rings into them.
John

[calj737]

I will offer this bit of advice: I personally would never use brushes or chisels on pistons or other aluminum parts. Brass and chisels will chip, scratch and gouge aluminum. A soda blast or chemical bath is best to remove carbon.

I like to use antifreeze to remove carbon. Boil some in a metal bucket, drop your pars in for about 10-20 minutes and remove them. They should be shiny and clean as a result, it's not caustic to your parts, and will not attack the aluminum.

[John Eberly]

I will offer this bit of advice: I personally would never use brushes or chisels on pistons or other aluminum parts. Brass and chisels will chip, scratch and gouge aluminum. A soda blast or chemical bath is best to remove carbon.

I like to use antifreeze to remove carbon. Boil some in a metal bucket, drop your pars in for about 10-20 minutes and remove them. They should be shiny and clean as a result, it's not caustic to your parts, and will not attack the aluminum.

I agree on the anti-freeze. I've used it on lots of aluminum parts and things like R/C airplane engines that get gunked up with burned castor oil.

I use a cheap Wal-Mart crock pot to "cook" parts in green Prestone.

[Stev-o]

I personally would never use chisels on aluminum parts.

I've used a sharp chisel to remove gaskets from alum case, but you have to be very careful.

I've bought a new tool to remove gaskets and works great...

https://www.amazon.com/3M-07480-Coarse-Surface-Conditioning/dp/B0002STR90

[strynboen]

mine 550 had melted a piston..so needet a repareir..but i reused 3 pistons as they vas vell in spec..did a valve job,, put one nev piston inn..and used a new gasket set..cam thain vas thanged..but the tensioner vas re used..just Flex honed the bores..leightly..and put all parts in the korrekt place..so no- thing vas mixed up
dont fix/thange parts vho are as good new..specily in this days..hvere aftermarked parts not alvays are the same good kvality as the orginal parts

some rebuilds ends up vith a vorse engine as before they started up the job..550 engines can run over 100,000 km only need a camthain/tensioner at halfvay..but almost all vill leak a bit from the head areia..