Carby Tuning advice for Keihin carb

Alright, I got an update. Got the jet kit and just by looking by eye the pilot is around a 35. I put in a 40, the biggest one, just to see the difference. I also moved the c clip down one from the top, it was at the top. I did actually have to turn the idle mix screw out to get it to rev higher, so it was lean. Don't ask me how that makes sense because it ran better when I moved the clip up and the spark plug looked black.

Anyway, a 40 was too big so I put in a 38 and it seems correct. The mix screw is now about 2 turns out to get the highest idle. Turning it out further doesn't affect the rpm. Stock main is around a 75 so I put in an 80. To be honest, with how much I up jetted I didn't think it would run. I still don't know if an 80 is correct, as it's been raining for 3 days straight so I can't do a top speed run or anything.

Still need to do more riding to make sure the pilot is correct as well.
 
Alright, I got an update. Got the jet kit and just by looking by eye the pilot is around a 35. I put in a 40, the biggest one, just to see the difference. I also moved the c clip down one from the top, it was at the top. I did actually have to turn the idle mix screw out to get it to rev higher, so it was lean. Don't ask me how that makes sense because it ran better when I moved the clip up and the spark plug looked black.

Anyway, a 40 was too big so I put in a 38 and it seems correct. The mix screw is now about 2 turns out to get the highest idle. Turning it out further doesn't affect the rpm. Stock main is around a 75 so I put in an 80. To be honest, with how much I up jetted I didn't think it would run. I still don't know if an 80 is correct, as it's been raining for 3 days straight so I can't do a top speed run or anything.

Still need to do more riding to make sure the pilot is correct as well.
A black sooty plug is an indication of lean running. Now if you are having trouble starting it or keeping it running, that Unburnt gas will wet the soot and plug and make it look like it was running rich. If you look at your piston and it's all sooty, it's lean. Or flip the piston over ( after a little bit of running it) and it's burnt black, not oily brown, it's lean.
 
A black sooty plug is an indication of lean running. Now if you are having trouble starting it or keeping it running, that Unburnt gas will wet the soot and plug and make it look like it was running rich.
I choose to believe this for my own sanity. The only thing I wonder now is why it ran better with the c clip adjusted leaner.
 
lean is mean, till it blows. If you are running a 2 stroke for just fun or commuting, you run richer. Lose some power yeah, not that much though. Extra gas cools, extra oil lubes and cleans. Now you run mean and lean to a degree when racing. Not way lean, but a lot hotter than a fun bike. Mean and lean kills, but makes more power. It wears the engine sooner. You want a bit of richness to keep your baby running a long time.

you can tell if you've been running to hot, by looking at the bottom of the piston, or even the top. If there is an oily residue that is brownish and wipes off easy, your good. If its hard and black, you're to hot. Heat makes soot, rich burn doesn't heat up enough for a lot of soot to form, and what is, is washed away.
 
Update #2: 80 main was a bit too big, started four stroking at high rpm and it went faster when I let off the throttle a bit. I got a speed of 36. Went down to a 78 and got 41! My goal was to break 40 with this bike, so I'm happy.

Took the head off to inspect the inside. Everything seemed in order except there was a black patch on top of the piston (not the whole piston, only about half). It wiped right off though, and I'll keep an eye on it. Other than that, it's what you described, a brown oily film that can be wiped off easily. No scratches or anything on the bore. Didn't look like there was blow by on the piston.

A few concerns though: One is that my base gasket is wet, like the whole thing is wet out to the edges. I put rtv on it. A common theme on these engines it seems. I believe all of my gaskets currently have rtv on them. :ROFLMAO: The second thing is that I have a CNC high compression head (https://bicyclemotorworks.com/product/cnc-high-compression-head/). I looked at the part where if you were to sand it, that's would it take material off (sorry, I don't know what it's called) and there was that film of the inner half of it, if that makes sense. I also have a compression tester that says it only has 50-60 psi. That doesn't sound right to me because I don't think it would run with that little. I know the first order of business is to check the squish, which I will do tomorrow as I don't have solder on hand. Any advice?
 
Your piston will be a little dark from running it rich with that 80 jet, check it again after some miles.

If you place your head gasket on the head, does it run all the way to the inner edge?
 
If you place your head gasket on the head, does it run all the way to the inner edge?
Nope, it only covers up half of it, which is why the inner half has oil+gas on it. I honestly didn't know if it's supposed to be like that, but I figured it must be because the gasket matched the bore. ¯\_(ツ)_/¯
 
Nope, it only covers up half of it, which is why the inner half has oil+gas on it. I honestly didn't know if it's supposed to be like that, but I figured it must be because the gasket matched the bore. ¯\_(ツ)_/¯
Have you try to measure the diameter of the inner lip on the head as compared to the cylinder?
 
Have you try to measure the diameter of the inner lip on the head as compared to the cylinder?
Didn't measure it, no, but the diameter of the dished out part of the head is smaller than the cylinder and hole in the gasket. I made this little picture to make sure we're on the same page.
 

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