Upper tear down question/pole

yup79 · Feb 8, 2016

Hi all, new here...question...

I have a 1980 xs650 motor that I've bought a new cylinder head for due to a stripped spark plug hole...should I keep tearing it down and replace the rings...it had good compression before taking the head off...

What do you all think?

:thumbsup:

figure8 · Feb 8, 2016

Why not just put the new head on, torque it down and check compression? If it's good you'll save a big step.

5twins · Feb 8, 2016

How many miles on the motor? If it's 20K+, it could probably use more "fixin". Rings, cam chain, and front cam chain guide are the usual items that get replaced. Replace the valve guide seals too, they're 30+ years old. The valves usually need to be lapped to fix minor leaks as well.

NONclow · Feb 8, 2016

How new is new anyway? Any actual readings for "good compression"?

If you'd trust the "new" head as being refreshed, the rings won't be that new(,or will they? Hmmmmm... :wink2:

), and thus will wear quicker. If the valve/seat relationship is weakening but the rings seal better, the valves will burn/crack/snap/fail sooner.

Why trust it? You're already in elbow deep.....................

gggGary · Feb 9, 2016

I am comfortable with my foot gauge for "purchase" decisions but this size 10 has a lot of XS experience and comparisons with the gauge reading.
Short answer is it's all up to you. If it's a quick flip or bar hop bike sure button it up and go. If you expect to ride it distances, and keep it for years make it $trong and reliable. Valve seals are smart anytime you have the head off.

fredintoon · Feb 9, 2016

yup79 said:
Hi all, new here...question...

I have a 1980 xs650 motor that I've bought a new cylinder head for due to a stripped spark plug hole...should I keep tearing it down and replace the rings...it had good compression before taking the head off...
What do you all think?

Hi yup and welcome,
well, this ol' bodger would fling the new head on and see how well it ran before I dug further into the engine.

NONclow · Feb 9, 2016

There's never enough time to do it right, but always time to do it again! :doh:

Sure it may work. But for how long? 5 miles, or 5 years? This rapid repair could turn you off of these bikes if it manifests into an easily addressed quirk you can go crazy trying to find, that could be caught soon enough as to not cost MORE money for the same (or similar) job....AGAIN! :twocents:

5twins · Feb 9, 2016

The rings don't concern me as much as the front cam chain guide does. If it's the original, it's probably about the most failure-prone item in one of these motors. The last motor I helped a guy with was pretty good inside. We got away with just a hone and new stock size rings. But that front guide was toast. The rubber strip had fallen right off and was bouncing around down on top of the crank.

yup79 · Feb 9, 2016

Thanks guys for all the responses!!

I have no idea of the miles on it and can't remember the compression as I tested it last year. It's been sitting in my garage since. I have pulled the valves and seals and will be cleaning and replacing them. I may as well go ahead and hone and re-ring the pistons since I'm changing the head out.

I'll check out the front cam chain guide, thanks 5twins.

:bike:

fredintoon · Feb 9, 2016

Hi yup,
and yeah, o'l bodger had forgotten about the need to check the self-destructing cam chain guide.
Now is the time to feed the engine a new one.
Hopefully the pistons/bores/gaps are in good enough shape that a hone & ring job is all you'll need.
Note that ANY discernible rod/wristpin movement, up & down rod/crankpin movement or main bearing roughness will signal the need for a bottom end rebuild.
And check the oil pump too.

Upper tear down question/pole

yup79

XS650 Member

figure8

XS650 Guru

5twins

XS650 Guru

NONclow

Confirmed Laquer Breather

gggGary

If not now, When?

fredintoon

Fred Hill, S'toon.

NONclow

Confirmed Laquer Breather

5twins

XS650 Guru

yup79

XS650 Member

fredintoon

Fred Hill, S'toon.

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