Hi,

Are you aware of any particular reason why the exhaust port bridge plating should crack. Last thing I want to do is locate another cylinder for that one to fail in a similar way.

My 21R is standard apart from the splice. All carb settings are standard. Plugs suggest it's running fine and I know each nsr reacts differently to jetting.

If the crack has develoved as a result of the rear cylinder running too hot, would you think it's wise to go up a size on the main jet?

Mark.