1970 Yamaha CT -1B, (question)?

Question

I was given this motorcycle for something to tinker on and maybe restore. It is still in really good shape. My question is it has two spark plugs but only one coil and coil wire. Why is this?

Answer 1

The hole that holds the spak plug at the rear was designed to put a compression release if you rode off road.It does not hurt a thing.Their was a bolt to plug it off stock.

Answer 2

simply because some designers do this to ensure all of the fuel is burned in the combustion chamber, this way they get more spark in a larger area of the chamber. good for a bit more power and more efficient. Some modern bikes still are made like this.  

Answer 3

The second hole was designed to install a compression release device.

I had a similar model Yamaha and left 2 spark plugs in the head.

When one plug got fouled, I just switched the spark plug cap to the other plug.

Answer 4

interesting, it is a single cyclinder 2 stroke bike. it only needs 1 plug to work, i would bet that because it has 2 plugs (Roadstars also have 2 per cyclinder) that you could hook the wire from the one plug that fowls to the next without pulling a plug out. I cant find a coil listed for that bike, however if your manual shows 1 coil with 1 lead thats what its for. If your manual shows 1 coil 2 leads then someone couldnt find a replacement and made due with the 1. manuals are on sale online.

i did find the skematics for you bike online at http://www.cmsnl.com/yamaha-ct1b-1970_mo...