Scratch in Cylinder - Rebore?

[XSRocket]

Hi all!

I picked up my '82 XS650 about a month ago. It seemed to be running alright, but was a little tough to shift. I drained the oil to change it and check the shifter springs (one of them was indeed broken), only to find a LOT of metallic shavings on the plugs and sump filter, a bunch of aluminum and plastic in the other filter, and oil so dark I don't think the PO ever changed it...

Long story short I pulled the head off to replace the cam chain tensioner, and have been checking everything else out as I go. Things seem pretty ok, even the piston rings are all in spec, but I found this scratch in the right cylinder.

It seems pretty deep - I have a feeling this means a re-bore, but I was hoping some experts could confirm for me. How bad does it look?

 

[Jim]

First off.... welcome to the forum.
Your 'scratch' looks more like a crack in the cylinder wall. Either way, it ain't good. I think rather than boring it, I'd consider re-sleeving it.

 

[Jim]

If it were me, I'd remove the sleeve and see if it's cracked through.
Here's how to remove the sleeve.

 

[XSRocket]

Thanks!

Here's a clearer picture of the damage. It seems superficial, but maybe I'll heat up the oven since it doesn't seem like I'm putting the head back together today anyway.

 

[xjwmx]

The rings are messed up, and maybe the piston on that side too (wear in groove). Cheapest thing is probably look for a cylinder that's in spec. Sleeves are more expensive than cylinders. Need cyls, rings, maybe 1 piston.

 

[Jim]

From that pic it looks like corrosion. If it sat for an extended period on the sidestand, that's where the moisture would puddle

 

[xjwmx]

Yes, don't know which pic is more like reality.

 

[XSRocket]

I think the pic in my second post is a better representation. It does look like corrosion in direct light.

If that's the case, does that still look like too much to be cleaned up with just a hone and new rings? You can just feel it with a fingernail, but the edges are smooth enough that it seems like the engine's been run a while with that there.

 

[xjwmx]

Did you ever test the compression?

 

[Jim]

If you can feel it, it's doubtful just a hone will clean it up.

 

[XSRocket]

I hadn't tested the compression - figured I would once I got it all back together and adjusted the valves.

Guess I'll start calling around about a re-bore. Should I have the new pistons and rings already before I take it to a machine shop?

Thanks for you help!

 

[Jim]

Before you go the re-bore route, contact forum member @gggGary and see if he has a matching sleeve and piston. That's probably gonna be cheaper than a re-bore.
If you do go the re-bore route... yes give them the new piston so they can bore it to match.

 

[weekendrider]

I think it is a crack. A scratch would have a cleaner/straighter line? If it is I (like XJ) would consider getting a whole cylinder package (gggGary may be of help).

 

[Jim]

I think it is a crack. A scratch would have a cleaner/straighter line?

Yeah, I'm still leanin' that way too. I'd still recommend pulling the sleeve and checking. Be a shame to spend all that money on a bore only to find out it won't clean up....

 

[XSRocket]

I'll pull the sleeve tonight and report back

 

[TwoManyXS1Bs]

The threshold of human touch is about 0.001". Any surface aberrations that can be felt means a rebore. Don't order pistons/rings without first knowing the current cylinder size, and predicted final bore size...

 

[XSRocket]

No cracks!

The heat did bring it out some rust(?), Just on that sleeve, seems to wipe off easily. Left side stayed clean.

Now for a little bit of research.

 

[XSRocket]

As an update, it sounds like Gary doesn't have anything handy and I've been looking into local machine shops (anyone have a favorite in the LA area?).

Given the price of a new sleeve on Mike's, it seems like it'll come out cheaper to get a set of cruzinimage pistons and rebore what I have. I'll bring the cylinders into the shop before I order because I'm a little concerned +0.5mm won't be enough.

Just to cover my bases, is it a bad idea to use an old piston in a new sleeve? Between new rings, new sleeve, honing the old cylinder and fitting the new it's probably still less cost-effective, but I wonder.

 

[MaxPete]

As an update, it sounds like Gary doesn't have anything handy and I've been looking into local machine shops (anyone have a favorite in the LA area?).

Given the price of a new sleeve on Mike's, it seems like it'll come out cheaper to get a set of cruzinimage pistons and rebore what I have. I'll bring the cylinders into the shop before I order because I'm a little concerned +0.5mm won't be enough.

Just to cover my bases, is it a bad idea to use an old piston in a new sleeve? Between new rings, new sleeve, honing the old cylinder and fitting the new it's probably still less cost-effective, but I wonder.

YES - in almost every case, it is best to take the cylinder to a machine shop before ordering pistons and rings as you just never know what the final size will be. Once they've had a chance to measure everything and perhaps even bore it out to an over-size dimension - THEN - you obtain the other parts to match the cylinders.

This will add a bit of time to the entire process, but in the long run, you will save money and come out with a much better job that will be more durable in service.

Pete

 

[TwoManyXS1Bs]

... is it a bad idea to use an old piston in a new sleeve?

Generally speaking, yes.

If the old piston is undamaged and skirt measurements show no wear (highly unlikely), it can be reused.

Imagine building up a new wheel, hub-spokes-rim. Then someone wants to put a used tire on it. Dunno, almost new, or is the cord showing...