Rust on piston and valve

[Guest]

So I picked up a 1980 gs 850 last week and started breaking everything down to see what I was working with. There was water in carb #4, and only in number 4. Likewise there is rust on the valves and on the top of the piston #4, and only #4.

So what do I do? I have searched and read about Marvel Mystery Oil and similar stuff. Will this be enough to take care of it? Or is it already too bad that I need to be doing something else?

Here is a pic of the valve. Can't get a good pic of the top of the piston, but I can see it through spark plug hole with a flashlight.



Best one I could take.

[Nessism]

Any idea how long the water was in there? The cylinder wall is likely rusted as well as the valve and seat. The extent of the damage is unclear though. Guess it wouldn't hurt to try to run the engine. Worst case is you tear the top end off and fix it.

[HighCountryGS]

Any idea how long the water was in there? The cylinder wall is likely rusted as well as the valve and seat. The extent of the damage is unclear though. Guess it wouldn't hurt to try to run the engine. Worst case is you tear the top end off and fix it.

I have no idea how long the water was in there. The PO said he rode it before the winter, but said it may not have been firing on all cylinders. But, I'm not going off of what he said, just what I can see. Cylinder looks like it might actually still be wet, but hard to tell.

[nejeff]

I have no idea how long the water was in there. The PO said he rode it before the winter, but said it may not have been firing on all cylinders. But, I'm not going off of what he said, just what I can see. Cylinder looks like it might actually still be wet, but hard to tell.

Was there water in the oil when you drained it? I would drain oil & take out filter and see what's going on. I would leave both unplugged and open. Use a water displacer (wd-40) in the that cylinder (or even all) spray through intake side and sparkplug holes. Let sit for a couple days and then put a tablespoon of motor oil in each cylinder and turn over with a wrench a few times, do this for a couple days and then the new oil, filter and away you go. I am assuming while the carbs are off your going through them so you'll maybe have the time to do this. This is what I would do personally and just did it on a Honda Nighthawk that had not been run in several years and results were very good

Like was said before you could just run it and see what happens. Hopefully this may mitigate some damage

[chef1366]

If it's a rat bike run it.
Long term take off the top end and have a look.