It took me back to being a 16yr old and wondering how mean I could be to the exhaust port on my FS1E. Armed with a rusty round file that was for sharpending chainsaw blades I made my first attempts at porting. No internet and forums to read up with, just tried and failed to start with.
http://www.preloved.co.uk/fuseaction-forums.showdiscussion/thread_id-6547/41c3096b.html
Have a look at the thread in general - I wonder if they all ended up owning Yamaha's too ?
and hanging around on the net
Sorry Andy, just had to.
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These aren't the droids you're looking for.