It ain't perfect but I do believe it's a big improvement! Sanded the exhaust port using the butt end of a punch. Used 150grit to sand the cylinder but I'm not done yet. It was about 1/16" of carbon build up on the exhaust port. Yuck.
Opening up the baffle behind the muffler outlet will help knock down on the carbon buildup in the future
The airflow must have been restricted at least 10% with all the carbon buildup! How do you prevent that build up in the first place? Using a quality fuel like Motomix or VP or Truefuel isntead of gas station gas + oil I presume. You can't really clean it without taking out the head, right? Otherwise all that crud would wash down into the crankcase. I was planning on drilling a few holes yes. Also going to hit the outside of the muffler with a wire wheel and some wd-40 to get rid of the rust and make it look halfway decent again. Lastly I also noticed that the lower piston ring stop - that little notch that keeps the ring from rotating into the intake and exhaust ports - was broken and allowing it to rotate. So another reason to put in a new piston and rings. Can I use a dremmel with a sandpaper attachment to polish up the exhaust port a little? Still looks like it could use a little cleaning up.
Better oils and better fuel can prevent most carbon. Mostly the oil. Yes, just be careful not to remove the factory bevels at the plating.
And I just saw a video that said polishing it up the exhaust port will help prevent carbon from sticking in the first place too, right? You mean where the gasket sits i.e. the outer most part of the port? I'll just focus on the inside. It would have been better and easier to polish if it was round, n'est-ce pas? I wonder why they made the shape like this. I'm thinking about taking a screw driver and cutting a slot into it to make a mandrel so I can hold the sandpaper more securely. What do you use to polish an exhaust port? I plan to wet sand up to 600grit.
Yes I use a nail with a slot cut in it. 80 grit dipped in spray oil is smooth enough. The paper dulls and will leave it considerably smoother than you’d think. No, the inside. Where the rings ride over the port. As the piston goes up and down, the rings expand out into the port a little. The port has an arch in the roof and floor to help ease the rings back in. Without a bevel in the plating, the rings will snag it and ruin the cylinder.
Gonna order a set of these buffing wheels for the dremmel. Seems like a better approach than just the sandpaper attachment.
I don't feel a lip on the inside of the exhaust port...but I kind of see a bevel on the inside of the cylinder wall. Is that what you mean?
for a while now I have been using red armor oil at 40:1 and while I haven't pulled any cylinders off using a borescope it's looking pretty clean inside.
After this VP fuel runs out I think I'll go back to the Stihl Motomix. It's damm expensive but I really don't use that much fuel and am happy to have the premix ready to go. I don't like the smell of the VP exhaust fumes. I don't trust myself to keep tracking of what's mixed and what isn't as I have quite a few things that require straight gas.
Still waiting for the case splitting tool to arrive. Meanwhile I've had the muffler and an old crescent wrench sitting in a vat of vinegar and took a short video of it. Here's what it looked like when I got it.
Vinegar is wonderful stuff for sure. I keep a tub of it for removing mill scale from steel. The mufflers I've done I've painted with high temp paint and then baked it in the grill and it holds up fine.
Checked on the muffler and decided that was enough. Looks pretty bad azz just like this. Rinsed with water, dried with a towel, and then smothered with wd-40 to prevent flash rusting.
