G-9 Engine Rebuild - Valve Question

[Ktrilla]

I started a project a few months ago and received great advice on the issue I have, which is lots of smoke. I have the engine taken a part and the new piston rings are installed. However the valves have a lot of carbon buildup. I am afraid to start screwing with these if it’s a hassle.

Thoughts on their condition? Should I mess with them?
If I should clean them, what’s an easy fix.

Thanks everyone!

[raydhd]

IMHO you clean things up and replace the the intake valve seal while the engine is apart.

[CP241]

If it was smoking there’s probably a significant amount of carbon buildup in the exhaust port under the valve.

If the engine is apart, why would you not take the valves out, inspect them for wear, replace the seals, clean them up on a wire wheel and re lap them back in? You may as well do the job the right way... it’s a lot easier to do it now (30 minutes) than to have to take it all apart and do it again later. And if there is carbon buildup in the exhaust port it’s going to restrict flow and the engine still won’t run like it should.

[slonomo]

Originally Posted by CP241

If it was smoking there’s probably a significant amount of carbon buildup in the exhaust port under the valve.

If the engine is apart, why would you not take the valves out, inspect them for wear, replace the seals, clean them up on a wire wheel and re lap them back in? You may as well do the job the right way... it’s a lot easier to do it now (30 minutes) than to have to take it all apart and do it again later. And if there is carbon buildup in the exhaust port it’s going to restrict flow and the engine still won’t run like it should.

Good words. I use a good clean brass brush and some solvent to clean that carbon off. If you have a glass bead cabinet you could also do that if you disassemble the valves etc.

I would also check the gasket surface with a good straight edge. I have trued up heads on a large flat surface (glass table) with a sheet of sandpaper glued to it, just run back and forth in multiple directions. You can use a dye to color the surface and check it after you sand, that will show the low spots.

[CP241]

Originally Posted by slonomo

Good words. I use a good clean brass brush and some solvent to clean that carbon off. If you have a glass bead cabinet you could also do that if you disassemble the valves etc.

I would also check the gasket surface with a good straight edge. I have trued up heads on a large flat surface (glass table) with a sheet of sandpaper glued to it, just run back and forth in multiple directions. You can use a dye to color the surface and check it after you sand, that will show the low spots.

Sharpie works well too instead of dye. Just have to clean it good with brake cleaner first

[slonomo]

Originally Posted by CP241

Sharpie works well too instead of dye. Just have to clean it good with brake cleaner first

I have done this, but it does rub off easier than the dye. I finally went and bought the dye lol. Problem with that stuff is it DOES NOT come off the skin!!

[Ktrilla]

Thanks everyone! Main reason isn’t to be lazy but rather skill set. I’ve never done something like this and I am trying to avoid “doing to much”. But I agree, better do the job right and take the time to learn.

Since it is Saturday, all the dealerships are closed. Any chance I could get lucky and that the valve seal is standard? Could I get away with a non Yamaha part? Just a shot in the dark...

[Ktrilla]

Another question... getting carbon off the side shown in the photo seems like a no brained... but is there a test I can do to see if the valve is well sealed without taking it a part?

[CP241]

Originally Posted by Ktrilla

Another question... getting carbon off the side shown in the photo seems like a no brained... but is there a test I can do to see if the valve is well sealed without taking it a part?

Yes. Get some lapping compound and lap them.

Rather than trying to describe how to do it, check YouTube. There’s plenty of videos on lapping valves.

[slonomo]

If you don't have a lot of engine experience I recommend a good factory service manual for your cart and some basic small engine educational videos and/or books. Your local library probably will have some books if that's your thing. YouTube is filled with videos, some good, some great, some garbage. If you are doing "anything" for the first time, it's a good idea to have a buddy locally that can help you or at least guide you. We can help you here, but you'll need to post lots of photos etc, and it might be slower than if you have someone live. Glad to help.