Tore my motor down and not happy (w/ pics)

[WesV]

Originally I just wanted to replace my base gasket and do a valve adj. Once I pulled the head I realized this thing is gonna need more work then that. The amount of carbon build up on both the valves and the pistons was more than I was expecting and needless to say, we can see that none of the cylinders were running perfectly. I knew one cylinder (#3) was definitely lean before I tore this down, but it is real obvious now. In the pic of the head, #1 is on the right.

So.... now, opinions? I am thinking about getting the valves ground and not real sure what else I really want to do. I am on the fence a little because the bike ran decent while I was running it (aside from needing the valve adjustment and the #3 richened a little) but just being me, I can't put it back together like this.

[Nessism]

Looks like a perfectly normal engine to me; all engines build up a layer of carbon inside which is nothing to be concerned about. The pistons look pretty good as near as the photos show; can’t see much in the way of brown streaking down below the rings which means the rings were sealing well.

I suggest you decarbon the combustion chamber with a wire wheel and then pull the valves out (keep them in order so you know which hole them came out of). Check the valve faces for pitting and/or burning from lack of valve adjustments. Assuming everything is normal, you can do a simple lapping job and install new seals. For the cylinder and pistons, a deglazing and new rings would be the way to go if the engine is under sty 50k miles. If 50k and above I’d get the cylinder measured for wear before paying for new rings since you may need a bore job.

You’re off to a good start. Keep going…

[WesV]

Now that I am doing a little more looking, it might not be as bad as I imagined. I am used to tearing apart large V8s and not bikes, so all the carbon build up spooked me a bit. After about an hour of searching and reading other threads, I think that I have a little better game plan now.

Clean and lap the valves (assuming they are in spec)
Replace valve seals (motor has 60K on the clock and I don't believe it has ever been opened.)
Clean carbon off pistons
New Rings

Sound about right?

[WesV]

Looks like a perfectly normal engine to me; all engines build up a layer of carbon inside which is nothing to be concerned about. The pistons look pretty good as near as the photos show; can’t see much in the way of brown streaking down below the rings which means the rings were sealing well.

I suggest you decarbon the combustion chamber with a wire wheel and then pull the valves out (keep them in order so you know which hole them came out of). Check the valve faces for pitting and/or burning from lack of valve adjustments. Assuming everything is normal, you can do a simple lapping job and install new seals. For the cylinder and pistons, a deglazing and new rings would be the way to go if the engine is under sty 50k miles. If 50k and above I’d get the cylinder measured for wear before paying for new rings since you may need a bore job.

You’re off to a good start. Keep going…

Thanks Nessism.
I was reading a very similar reply from you to someone else earlier which is what got me on the track of my reply. Honing the cyl walls was already a given and they look really good for 60K IMHO. I can just barely make out a little bit of the cross hatching here and there, but they certainly aren't new.

[Larry D]

Here's what my '81 GS750L looked like when I took it apart. No problems, just dunked the pistons in some Berrymans for a few days and the carbon came right off.

[gixerbike1]

New Rings

Hey Wes,

You might want to check the rings you have to see if they really need to be replaced.

Something else, you might also want to have the cylinders cross hatch honed if you go with new rings so they will seat properly.

Other than cleaning things up real good with some new gaskets and Valve seals and lapping, you should be good to go.

Good luck with it and keep us updated.

[teddux]

Now that I am doing a little more looking, it might not be as bad as I imagined. I am used to tearing apart large V8s and not bikes, so all the carbon build up spooked me a bit. After about an hour of searching and reading other threads, I think that I have a little better game plan now.

Clean and lap the valves (assuming they are in spec)
Replace valve seals (motor has 60K on the clock and I don't believe it has ever been opened.)
Clean carbon off pistons
New Rings

Sound about right?

If you were happy with the compression BEFORE tear-down, and oil consumption was normal:
Without disturbing rings, I would reassemble with same rings.

I would be more concerned on carb jet erosion...especially on the other 3 cylinders.

[tkent02]

Now that I am doing a little more looking, it might not be as bad as I imagined.

Sounds like you are used to modern fuel injected engines, which don't build much carbon at all. That looks completely normal for a bike that's been a bit rich.

[hampshirehog]

Solid looking motor there - I agree with the others, it all seems completely normal. Clean everything up, measure everything and replace the valve stem oil seals. If it's done 60k I'd replace the rings and hone the bores. Might not need doing but it's cheap enough and easy enough while you've got it stripped down.

[chef1366]

Looks like a medium mile well jetted engine to me.