I have a '77 Foxi GT with the Sachs 504 engine. It was running fine when I got it, but a few months down the road, it started to make a horrible noise when stopped at lights. It sounds like metal rubbing together, or slamming together, like a 'clank clank' then it stalls out and the back wheel locks up. It doesn't go as fast as it used to and I feel like it is slowly dying.
The carb is clean and I put new gaskets on it.
I have opened up the cylinder; the piston and rings looked fine. I cleaned off the piston a bit and rubbed oil all over it before I put the cylinder back on. It's still making the noise, and the back wheel still locks up at times.
It still starts up every time and rides fine (other than the slow speed), but when it's supposed to idle like it used to, it locks up and conchs out.
Any ideas? I have a few, but I am not sure where to begin. I thought it had something to do with the bearings, since that is where it seemed to lock up, but again, everything is connected anyways. Jae says it might be soft seizing and to add some fluid to it (I don't know what to add).
Also, I am having trouble undoing the screws on the engine to open it up. I put some liquid wrench on them, no help... I am going to buy an impact driver, hopefully that will help.