1. How long have you owned the bike?
2. Has it done any long term sitting?
3. Who did the modifications?
4. How do the plugs look?
5. Is the problem the rpm hang?
Thanks for the reply. Answers and more info:
1) Since December.
2) The person I bought it from has two other bikes, so this one was not used as regularly as it will be now. He purchased it from someone who could not ride any more in 2005 and put about 5 K on it. So yes, it's safe to assume it has sat at least for the winters. here in NE PA.
3) The carb/HC install and pipes were installed by the first owner.
I did most of the 20K service over the winter (cables, brakes, replaced bearings chain sprockets, etc) I did not do the top end service (valves-etc) yet nor have I done a carb tear down. I did run seafoam through the carb procedure when I first got it.
Now that the spring weather is here I put ~450 miles on it so far.
I have been adding approx 1 ounce of seafoam per gallon with each fill-up as well as the appropriate dose of startron for the ethanol (approx 1/2 ounce per 4 gal)
I replaced the exhaust gaskets as they were both leaking, but particularly the rear. And properly torqued the exhaust. No more leaks.
I removed the EPA valve/hoses and installed caps on the corresponding reed valve and airbox connectors
The pipes had no baffles, I installed cheapie can opener type but was never happy with the sound so I recently installed HP-Plus baffles (free flowing).
4) Front looks normal, rear was sooty black.
5) RPM hang seems to be much less now that I have the AF mixture screw set at 3.5 (it was at 4).. It was doing it pretty consistent when reving 6-7K+, now it seems to do it occasionally, but not for nearly as long. Not sure if some amount of hang is normal or not.
Other thoughts: I'm not sure of this makes as much difference as I think it does, but I also have been driving it differently now that I am used to it. When in between gears, so to say, I leave it in the lower gear to keep RMS up rather than bog down by shifting up. Example, criusing a back road at 50 I'll leave it in 4th. Especially now that I lowerd the RPM by ~200 by installing 17/40 sprockets. But I am not sure how much difference that will make. I have a lot of engine experience from my youth working on cars in the late 70's - early 90's, but bikes (working on them) is somewhat new to me. I'm *assuming* lower RPM will exasperate any symptoms associated with running rich, like fouled plug(s) or valves.