1966 YL1 Rings Replacement

Hello all,

I am dealing with what is likely low compression on a 66" YL1 that I just got started for the first time in 20 something years. I have never replaced ring on a bike before. My question is when I take the engine off of the bike to replace the rings, are there any other components I should definitely replace/check while I have the engine off? Hoping to kill multiple birds with one stone if needed.

Thanks in advance

I would buy a piston kit and replace both piston upper bearing and rings. this is normal for a 2 stroke for these parts wear. when you get them out you need to measure the pistons and check them. the pistons will be stamped on the dome if they are oversize. you do not have to remove the engine to change pistons. you need to read the manual and they tell you step by step.


pull the cylinder straight off if you don't the rings hang up in the ports.

you need a tool to remove the wrist pin, it can be as simple as a long bolt through the wrist pin.

when you reinstall the cylinder make sure the end gaps of the rings line up with the pins in the piston.

BracketMaker,

Thanks so much for the quick reply. This is the first time I've heard that the engine does not need to be removed and I am very happy to hear it. I have a service manual and it includes piston maintenance in the same section as engine removal. I am much more confident now that the job doesn't seem so big. I will remove and measure the pistons tomorrow and report back. Thanks again for your help.

Bracketmaker,

I ordered new rings, bearings and copper gaskets. The rings that came have 4 rings in a box. Two of one type and two of another. Areyou familiar with this? The box says YL1 but I was under the impression that both the top and bottom rings were the same. I'm assuming the box came with 4 rings so you could replaced the rings on both pistons but I can't find any info on which ring should be top or bottom.

Attached is a picture of the rings I ordered. Two of the rings have a silver-ish outside and the other two are all black. They both seem to be the same size.

https://images.app.goo.gl/VB5qPBPUX4H2ca6J6

You need to look at the manual, generally they show the profile off the ring and which way needs to go up. Generally the manufacturer puts a symbol or some kind of indication on the side that will need to go up.

Always replace the gudgeon pin clips with new ones if you remove the piston. Install them so the gap in the clip is parallel to the motion of the piston (i.e. the gap faces toward the crown or the skirt of the piston)

Honestly, on a 2 stroke I would never do just rings without doing the next size up piston. Did you at least have the piston to cylinder clearance measured and the bore checked for roundness?