My bike has been running like crap the last couple of days... This morning, towards the end of my 11 mile trip to work, I actually had to get off and help push it up a hill.
Yesterday, I took the aircleaner apart and cleaned the element, and checked the plug. The plug was a nice toasty brown, like it's supposed to be. So today on my lunch break, I decided to take the exhaust off, cut it apart (mine is welded shut), and see what I could do with it.
It had lots of carbon inside, but didn't really look restricted. On a whim, I cut the muffler off the exhaust pipe and migged a new VW tailpipe in place. It looks pretty cool, but holy shit it is loud. Bike still ran like shit, and after running it for a mile or so, the plug showed that it was running too lean. I drilled the jet out one size, and ran it some more. Plug looked good, but the bike was still running bad. And loud.
Changed plugs, covered up the holes I drilled in the aircleaner, put another jet back in to correct for less air, tried different gap settings on the plug... I spent about 4 hours experimenting with different things, trying to get the bike to run better, always checking the plug to get the mixture right (yeah, I took a long lunch break)...
It is running better than it did this morning, but not much, and definitely not as well as it should.
Called the Yamaha dealer to price a new muffler. Discontinued.
My next step is to pull the head and check for carbon build-up. I may modify the holes that hold the CDI pickup on the flywheel to play with the advance, too. I'm also looking for a used bi-turbo to try on it, which I will have to weld to the exhaust pipe, since I'm sure no one makes one for my bike...
I'm guessing that a straight pipe exhaust is not really a good idea, performance-wise. I don't like all the noise, either. I don't like to draw attention from The Man, and I enjoy listening to the radio on my way to and from work...
1) Mine has a centrifugal clutch, which is pretty common on 'peds. I've noticed that the clutch will engage sooner with a heavier gear oil, and later with a light oil. I changed from 90w to 5w30 to 20w50, and now at least the clutch is working better...
2) The bike seems to prefer a larger gap on the plug than the book specifies.
3) The windshield amplifies, reflects and directs the exhaust noise directly into my ears and brain. Eh, what's that you say?!?
Any ideas from the gurus?