Topic: Can I Reuse These Pistons? And Some Other Engine Questions After Fire

[campbmic]

Hey everyone! About 6 months ago I mentioned there was a garage fire that my bike went through. I had a head gasket leak before that and needed to pull the engine anyways. During the fire the air pods melted and some water did probably get into the cylinders. I was able to get the engine out within a few days and did not see any water in the heads.

I wanted to get your opinions on what I should do next. My plan was to put the new gasket on, buy new piston clips, and put everything back together. All of the piston rings float freely and I don't see any damage. Please let me know what you think about the pictures and if I should buy new rings or have any issues with my plan. To me it looks like theres some "blow back" (oil or gas burned on the side of the piston) on one or two of the pistons. Not sure if this looks normal or not. Like I said, the rings seem to float free and look to be in good shape. I also want to mention rebuilt the top end about 10 years ago.

Also, I've never done a bottom end rebuild. Im kind of worried some of the crumbling dirt, gasket material, and junk may have fallen down into the bottom end. Is there an easy way to make sure theres nothing down there that could hurt the engine in the future? Im confident there's no metal or anything, but dont want some oil passage to get clogged up or something. Thanks a ton for all of the great info!

[69cb750]

Pistons are ok.
Measure piston od and bore size for proper fit.
Cylinders need cross hatch for rings to seat.

[bryanj]

As long as pistons go back in same holes and you are NOT changing rings no need to hone(cross hatch) BUT if new rings, which looking at the blowby would be a good idea, yes you need to hone. This is if clearances are not already too big.
As to dirt in engine remove the sump and wash everything out, change oil AND filter at 500 then 1500.

Also READ THE MANUAL CAREFULLY  on fitting cam cover then read it again at least twice so you dont bend valves

[Tracksnblades1]

Might opt for an 836cc kit.
Some tell tale signs of blow by.

Do you ride a lot, where your concerned
of the lifetime of just a rering?

Have you precision measured what you have?
Sometime measurements have a way of limiting
your options.

😩

[PeWe]

Check ring clearance on pistons so the groves in pistons are not too wide. Ribg should not vwiggle up- down in the ring groove. Honda manual has max clearance.

Pistons look ljke leaking rings. Bad seal due to slow break in?

Better to let bike taste the throttle direct with heavy decelerstions by thorttle offs  and use of gearbox when pistons with rings are  new after warming up.

I should replace them with next size. If stock, Cruzinimage has?
www.cruzinimage.net

[bryanj]

Be lucky to get 836 out of that as its a 500/550

[PeWe]

CruzinImage has pistons for CB550.
+0.5 mm
+1.0 mm
61.5 mm bigbore kit 600cc
110USD for oversize kits.

130USD for bigbore, head gasket included

[tlbranth]

Check for a ridge at the top of each cylinder. If there is one, borrow a ridge reamer from O'Reilley's and remove it. If there is no ridge or only a very small one, re-use your pistons, put on new rings and hone the cylinders. Check ring gap before installing on pistons. I always have cleaned up pistons with a fine wire wheel on a bench grinder (not the skirts). Ring grooves get cleaned using the square edge of a broken, old ring. Once you have the top end apart, it's not worth reassembling without new rings. I'd also do a full valve service. If you use only Top Tier fuel, you'll eliminate a lot of future buildup.

[Stev-o]

Be lucky to get 836 out of that as its a 500/550

HA!

[Tracksnblades1]

Be lucky to get 836 out of that as its a 500/550

Be lucky to get 836 out of that as its a 500/550

HA!

Oops, Didn't read 500/550.....👀😜

[HondaMan]

Well, you know my thoughts...at least a step-bore is needed, and the return for the effort will be far more power than before, and it will last essentially forever,  or 100,000 miles, whichever comes first...

[bryanj]

Neither did i but the oil feed holes at the ends of the cylinder give it away

[trigger]

Be lucky to get 836 out of that as its a 500/550

Come on now Bryan, you know how to get 836 out of a 500, you just put a 836 sticker/ decal on the side panel 

[jukku]

Be lucky to get 836 out of that as its a 500/550

Come on now Bryan, you know how to get 836 out of a 500, you just put a 836 sticker/ decal on the side panel 

In England it was called "badge engineering". Austin, Morris etc.

[campbmic]

So did we confirm that the dark oil/burn on the sides of the pistons was "blow by"? The plugs look like some of the cylinders were running more rich and some were running more lean, could that have anything to do with it? I wasn't burning oil as far as I know. The pistons that had the "blow by" were #2 and #3. I also had a really bad oil leak coming from the bottom head gasket. Could that cause this?

There's a honing tool you can rent from autozone that attaches to a drill. If I measure the cylinders and they are within clearance to put new rings on would this tool work? Or do I need something better?
https://www.google.com/aclk?sa=l&ai=DChcSEwjNr9rf6q7nAhVLvcAKHbdLD0kYABAJGgJpbQ&sig=AOD64_1cuhst2Ad_8vrxaa48U_pZWYhUOQ&ctype=46&q=&ved=0ahUKEwjtz9Hf6q7nAhVIAqwKHfzUC7IQvhcITg&adurl=

Last time I put new rings in, I used a snap gauge and micrometer. Is there a better way of doing it?

Im not looking for performance or more power or anything. I rarely drive more than 10 miles.

[bryanj]

More accurate is a bore gauge and micrometer

[tlbranth]

He doesn't have a bore gauge or a micrometer.
If the top end hasn't been previously messed with and there's no ridge at the top of the cylinders, there's no wear and no measurement is necessary.

[Kevin D]

Neither did i but the oil feed holes at the ends of the cylinder give it away

I thought they were 750's until I saw this clue:

[PeWe]

Flex-hone brush work fine to give a rough cross pattern surface for rings to seal.