GSXR1100 runs rough below 4000 rpm
Just bought a watercooled GSXR1100 registered in 96, though I understand it is actually a 95 model with 28,000 miles on the clock.
Unfortunately, I think I have been a little had over with it, as the guy I got it off didn't know much about bikes but he seemed very genuine, it was only riding it home that I discovered the issues. Most of which I can swallow, as they are old bike issues, i.e. rear spring instead of shock, i.e. no damping at all, clutch can't handle the power, so needs replacing , more likely upgrading, and fork seals on their way out.
However, the most concerning issue is the bogging down at low revs, it starts easily and ticks over fine, and above 4200 revs there are no problems that a new clutch won't solve. However, at low revs it is lumpy, and there is a marked flat spot from about 3900 up to 4200 when it then kicks in nicely. The guy claimed that the carbs had been balanced very recently, but to be honest, I have not yet started to look into the problem as to me, it seems like idle jets and or needle jets are either mismatched or worn. However there is an obnoxious Yoshimara Exhaust on it and I have no knowledge as to whether this would cause problems with standard jetting and standard air box. Would this pipe cause bogging down at low revs?
My first port of call will be to look at the plugs to see what they look like, then I was going to look at the carbs to see if they are clean and look at needles to see if the are discoloured before I start to do a complete tear down of the Carbs. I have had worn needle jets before on an EXUP as they only really last about 30,000 miles on them, however, my Fireblade has done 70,000 miles and is now only just demonstrating that a carb overhaul would give it some more bottom end back.
Some advice here from anyone with knowledge of gixxer carbs would be really appreciated. Happy to start tearing apart bits if it helps guide any experts here.