Clutch shaft? Do you mean clutch push rod? The 18 tooth front is close but if you keep the chain properly adjusted it won't hit the push rod.
From looking at your pic the wheel is pulled most of the way back. If the chain was the right length when installed, now it's stretched a lot. The sprocket looks worn too.
The 18 tooth front sprocket was put on the lower the engine rpms at highway speeds.
If you like that gearing you can just replace the sprockets with the same size and use the stock length 104 link chain. If you go to a motor cycle shop and look at a new sprocket you will see how worn yours is. The shiny spots on the sides of the teeth indicate to me the wheelwasn't straight in the swingarm.
If you look at the u shape betwee the teeth it should be the same on both teeth. yours look like the front edge is sloped forward. The rea edge looks straighter.
At the rear of the rear sprocket pull ther chain away from the sprocket If you can pull it more than 1/2 a tooth the chain is ready to be replaced. As worn looking as what I see in the pic I would put on all new. Mike's sprockets are good sprockets. His chain ain't the best deal. If you shop around you can get a good chain around $50 to $75. An o-ring can last longer than a standard chain.
