Little help? Chain...

[ApriliaBill]

My son has a 84 FJ600, needs a chain. I go on a site to buy and it asks size? Starts at 100 and goes to 140. What am I looking at? Amount of links, m.m.'s ??

[FJmonkey]

How many links are the bike now? Might be a good starting point.

[rktmanfj]

Googling it quickly shows three different sources calling it 106.   

[ApriliaBill]

Thank you, again, you guys rock!