I am trying to get an old Yamaha YCS1 180 twin running for my brother. I have only worked on the rotary valve motors and have a question on carb mounting. He got new insulators for the carbs as they were missing. Does the pin that sticks out of the manifold go between the pinch area where the carb mounting screw is? I noticed that area on the carb was marred up where it looks like someone tried to tighten the caI am trying to get an old Yamaha YCS1 180 twin running for my brother. I have only worked on the rotary valve motors and have a question on carb mounting. He got new insulators for the carbs as they were missing. Does the pin that sticks out of the manifold go between the pinch area where the carb mounting screw is? I noticed that area on the carb was marred up where it looks like someone tried to tighten the carb to tight without the insulators in. Is the purpose of this pin to serve as a locating for carb level? Thank you.   

Yes just as you say to get them both pointing upright. Pity they've been jangling around as not easily fixed. But at worst the manifolds unbolt to spin up & sleeve or something. Probably wouldn't really hurt to machine the manifolds then make alloy inserts to fit in place of the fibers with a small split for clamping. I dunno--wandering off course as usual.

On the rotary valve engines the carb will tighten onto the valve cover outlet. On this it will not. The only way to make the carb tight would be to tighten on that pin in the pinch area on the carb which appears to what was done. Would there not be an air leak if it would not tighten firm on the valve cover?

You mean reed valve on later but anyway. Yes was noting the carb has been moving around wearing out the manifold. & was thinking i can see it "manifold" bolts onto the cylinder so could remove & machine it then sleeve it to a nice fit in your new fiber bushes. By memory the fiber insert has a rubber piece in the end so when the carb is held hard forwad it seals on the face in the end of the fiber bush. They were a bit of a pain back in the day.

When he got it it had no inserts in the carb and the guy claimed it would run for a very brief moment. It took forever to find those inserts. The more I get unto this the guy was a hack. Got a small mess with the wiring.