Changing Timing Without a Key

[txluke]

Starting to work on the little 79cc. I already removed the governor. It is so much easier to pull the flywheel off and knock out the timing gear from the back. Everything comes out in one piece. With the flywheel off you can change the timing key. If you already know what timing you want then slap in the new key and go. I have no idea where I might end up with mods on this thing so I want my options unlimited. The key does not keep the flywheel from moving. The taper of the shaft and flywheel hold it. You don't need a key. The flywheel needs to be lapped to ensure a tight fit. This is simple. Add a little valve grinding compound to the shaft and turn the flywheel around, back and forth. clean everything well when done. When you don't use a key you have to know where to line up the flywheel. I took a tiny file and made a mark on the end of the shaft where the keyway is. If you want to advance your timing, you put it back on rotated clockwise just a bit. To retard the timing you just move the flywheel counterclockwise. Sometimes the flywheel moves when you tighten the nut so I like to give the flywheel a few smacks with a rubber mallet and then bump the nut on with my impact. Take the nut off and check if the flywheel moved. If you are satisfied, put the fan and cup back on and torque to spec. If you must know what timing you are running just print out a timing wheel and use it. There are plenty of YouTube videos on that.

 

[JTSpeedDemon]

Nice pics explaining the process, I was curious myself....
Thanks for clearing this up, I was too lazy to seek out a YouTube video on how to lap a flywheel.
I give this a sticky vote!