Does changing port timing affect air/fuel ratio?

[CuriousJojo100]

Hey everyone, this is a new account but I've been on this forum years ago. I've built many motoredbikes so I wouldn't consider myself a newbie but I am always hungry to learn more. With that being said, I want to know if changing port timing would affect afr

 

[Chainlube]

AFR is all carburetor. Port timing affects the way the charge moves through the engine.

 

[CuriousJojo100]

Thank you. I am on my second samger "100cc" (dropped a broken piston ring in the first one without noticing and it got into my combustion chamber). I just got it broken in. I love the torque on these but it falls on its face in the upper rpm range if I am on full throttle. Ports were horrible when I got it so I cleaned them a bit. There's still a lip all the way around the cylinder side of the intake and exhaust ports. Idk if that would have something to do with it. I'm thinking stock jet is too big but I'd rather fab up some kind of ram air over going with less fuel. Thoughts??

 

[GW's Motorized]

No matter wjat you do you should at least check the tune.

 

[Chainlube]

Thank you. I am on my second samger "100cc" (dropped a broken piston ring in the first one without noticing and it got into my combustion chamber). I just got it broken in. I love the torque on these but it falls on its face in the upper rpm range if I am on full throttle. Ports were horrible when I got it so I cleaned them a bit. There's still a lip all the way around the cylinder side of the intake and exhaust ports. Idk if that would have something to do with it. I'm thinking stock jet is too big but I'd rather fab up some kind of ram air over going with less fuel. Thoughts??

All the casting flash that protrudes into the ports has to be filed away to give nice smooth airflow. The cylinder side of the ports should be beveled so the rings don't snag on the side of the port, break off, and spoil your day.

 

[CuriousJojo100]

Normally I would have shaved away all of the casting in the cylinder side of the ports like I've done with every other engine but this one was different. The cylinder side of the ports were a lot bigger than I'm used to seeing so I was worries about making the ports too big and ruining my power

 

[CuriousJojo100]

The second pic is inverted. First pic is intake with piston at TDC and the second is exhaust with piston at BDC. I'm wondering if it will be safe to take all of that casting out?

 

[Chainlube]

The second pic is inverted. First pic is intake with piston at TDC and the second is exhaust with piston at BDC. I'm wondering if it will be safe to take all of that casting out?

Yes yes, get rid of all that . Don't forget to bevel the inner edge.

 

[CuriousJojo100]

I never forget to bevel it. Thank you for mentioning it though. I'm gonna do that tomorrow

 

[francisjohn]

The second pic is inverted. First pic is intake with piston at TDC and the second is exhaust with piston at BDC. I'm wondering if it will be safe to take all of that casting out?

I have worked on enough of these 49mm cylinders to know that is the 49mm bore/72cc, correct?

I love port timing and know these cylinders specifically like the back of my hand. I can answer any questions you have specifically on this top end.