rpms won't go above 3500 when in gear

I had the same problem with my bike and I knew it was in the carbs because I had just cleaned and adjusted (?) everything. Ended up one of the floats was hanging up in the float bowl and not letting right amount of fuel into the bowl, which ws starving the cylinder for fuel. One pipe would get red hot, and not rev. Once figured the carbs out, it ran great. BUT...check the ingition system like was suggested too. That will cause the same things also sometimes.

sorry it has been a couple of week since i have posted. i have been busy and out of town.

I did the coil mod and it seems to make some difference, however i still have problems at times, including that the plugs are still fouling.

When the bike runs "well" (relatively speaking) while in neutral the rpms will go up to about 8000. While in gear, the engine starts to sputter around 3500 rpms and tops out around 4500. I also cannot go above 45 mph.

When the bike runs "poorly" in neutral it will only rev to about 4000 rpms, and i am only able to go about 10-15 miles per hour.

I never know which i will get. I actually was riding it when it was running well, then in the middle of the ride it began to run poorly. It then backfired and began to run "well" again, relatively speaking.

When i started it up last, it was running "poorly" and i noticed that the right pipe was not getting hot. i do not know if it is getting hot when the bike runs "well"

It seems as though i have at least two problems. the first is what is causing the bike to run either "well" or "poorly". THe second problem would be when the bike is running "well" why does it not get above 4500 rpms while in gear and not about 45 mph (i used to be able to go 70mph).

I know this was a long post. Any ideas on where to go from here would be appreciated.

Did you do a carb sync?
Could be that your air/fuel mix is out of wack.
Running on one cyl has no power. Went through the same prob on my twin . It was the carbs.