more exhaust questions

[grifff]

After taking of my exhaust i notice that there is a hard burned
sooty looking material on the bottom part of all the exhaust manifold holes. it looks built up pretty good. Should i try and scrape that stuff out or just leave it? I'm a newbie so sorry if i sound stupid.

[Jerry]

Could be what you are seeing is the remains of the exhaust manifold gaskets. There is 1 per cylinder. Scrape the remains out and replace with new gaskets when you reinstall the exhaust pipes. Cost of new gaskets is $3 - $4 each. Yamaha part number is 432-14613-00-00.

[grifff]

thanks jerry, could any of the debri that i scape out damage the engine in any way it if goes inside the manifold?

[Jerry]

The gaskets are a sandwich construction with metal on the outside and something (asbestos?) in the middle. Typically when you start pulling out the old gaskets, the metal parts will come out looking like an old Slinky, spirals of very thin metal. The metal bits should not be allowed to get back into the engine. The organic parts probably would not hurt anything if they got back inside, but try to keep as much out as you can.

You should check the header nuts for tightness a couple times after you replace the gaskets and the engine has been run a few times. Leaks here can cause the engine to backfire on deceleration, so it is important the gaskets are in good shape and the nuts are tight.

I use socket-mounted metric Allen wrenches to remove or install the header pipe nuts. Not only faster than hand wrenches, but you can use a torque wrench to get consistent tightening on all 4 headers. (14 ft-lbs is the recommended torque.)