Help setting ignition timing on a Yamaha AT1 with a vape system.

[e30 gangsta]

Hello friends,

I am looking for the timing specification for a 1971 Yamaha At1.

I'm installed a new vape system and set the piston to 1.8 btdc.

I installed the base plate and made sure that the bolts were in the middle of the slots, then I installed the flywheel and matched the timing mark on it with the base plate timing mark.

Now my question is once everything is installed and aligned, how do you verify that the timing is not too advanced or retarded seeing as there is no external timing marks/pointer to reference with a timing light, besides the one on the flywheel and the base plate? Thoughts?

[1976RD400C]

Set piston at 1.8 and take a marking pen and make a mark anywhere on the rotor and then another mark on the backing plate that line up with each other. When the marks line up piston is at 1.8. Start and check if they line up using a timing light. If not, and you have to adjust the backing plate, you will have to redo the marks because you will be moving the backing plate and the original marks won't be at 1.8 anymore when they lined up.