Can I just replace the rings?

I have a '75 Honda CB125S with 13,000 miles on it.
Don't know the exact history, but it was stored in
a shed for years and years. I cleaned it up, but it's
getting increasingly hard to start when cold. Starts instantly
when hot.
Compression is 60. Shoot in some oil and it comes up to 120.
Looks like ring problem. Don't hear any piston slap.
I know it's hard to diagnose remotely,
but am I likely to be able to just replace the rings? If I have
to have it bored and get an oversize piston, it's likely not worth
the cost/trouble.
Suggestions?
Thanks, mike
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Oh yes. Those engines are incredibly strong, and it's unlikely to have
any bore wear at that sort of mileage.

 

Mike,
You're right about it being hard to diagnose remotely, especially in
the detail required.
13K is kind of a short life for rings unless there is rust damage
involved,
(a distinct possibility with long shed storage you mentioned).
The bores may be 'ringed`. If this is the case, you need a hone job
at a minimum, maybe a rebore, but you won't know until you open her
up.
If you don't feel a stiff spot when you turn the engine by hand
there's a chance its OK.

Best of luck with it,
Pragmatist -"R75/5 Forever!"

We are now ruled by a George II.
Doesn't history have a fine sense of irony?

 

I have a '75 Honda CB125S with 13,000 miles on it.

You may have more than ring damage... if the bike sat for a period of
time, you may also have some damage in the head... i had a similar
situation... low compression in one cylinder... half of that than the
others... turned out that the head needed to be welded and resurfaced
because there was way too much rust damage from sitting.....apparently that
particular cylinder had a vale open and condensation found its way in there
and time did its thing. I did the compression test and all too.... wasn't
just rings in my case.... but while you have the head off.. you might as
well just do a top end job... it may save you from having to go back and do
one anyway....

good Luck

Fwed

 

Tell me more about the additive. Last time I tried putting additives
in my bike oil, the clutch started slipping. Is this marvel stuff
clutch safe?

I tried selling the thing as an RV add-on, that's what I used it for.
Problem is that people who came to look expected to buy one for $50.

Don't have the RV any more. Been using the thing for garage sales
cause of the gas mileage. Not sure I want to go in for a
complete rebuild. Cost of pistons, etc makes my Scrooge-sense tingle.

mike

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Tell me more about the additive. Last time I tried putting additives

Well, it sound to me that if you don't wanna do a coplete teardown to
fix the problem, you will more than likely end up with the problem until it
gets fixed. You might be better off just selling it for the 50 bucks and
buying a new one, or maybe a good used one. One way or another, you will
have to bite the bullet on this one.....

Good Luck

Fwed

 

Pull the cylinders free up and clean the rings and glands by hand, hone it
out put it back together. Check the valve clearance while the top is off.
Hell if your careful you can probably use the existing gaskets. A little
black RTV goes a long way.

 

It's a single.

I wouldn't bother honing it unless it looks rusty.

Complete nonsense - check the valve clearances with the engine
reassembled.

Into the oil pump....

Well, that's this week's Crap Mechanical Advice posting taken care of.
next?