Need to know how to tell if a 750 or 1100 engine in my 1990 gsxr 750 also running lumpy at low speed micron system fitted but dont know if it has been rejetted

what kind of bike is it?what style of carbs? if it has rubber diaphragms in the tops of the carbs, you might have a pinhole in one or more of them.

run a can of Seaforam in the tank..purchase from Autozone put in 1/3 to two gallons gas drive it around for at least 10 miles to insure it cleans out the whole carb system.if that doesnt work, check all carb hose fittings when bike is at idle spray some Chemtool B-12 ( also at Autozone) around the carb hoses and manifolds..if idle increses thats your problem. Caution: chemtool is very toxic wear gloves and a mask.

replace lambda probe expensive but it will run ok after that, i dont know if you know how they work so here's a brief: lambda tells ecu how rich the exhaust gasses are, ecu ajusts fuel input as neccasery eg lambda says not anough fuel ecu puts more in and the other way round.
so if your lambda is covered in **** when you get it out just clean and put it back, if it looks clean enough it needs replacing!! jezza

you wont have any power steering for a start if its realy packed up,, but they do get kind of ***** and lumpy before they go,, look for oil leaks and also try turning the wheel from lock to lock at a stand still with the engine running , if it fells ***** look to see if the prowr steering oil is full up, if its low that can cause the steering to be lumpy,, if its low top it up and with the engine running turn the steering from full lock to full lock till all the air has been pumped out,,the steering should be smooth by then

the gsxr1100 cam will fit the bandit 1200 engine, i've done that mod 3 times so far. after that it's just exhaust and jetting.

clean the carbs!

No They are Different They Wont fit..

try calling a junkyard and see if they will tell you the enterchange ok good luck

This is actually designed to run at those revs. It\´s basically the best way to maintain reasonable power to wheels at high speeds with an engine that is not powerfull enough to produce the HP needed to maintain that speed or higher speeds with a higher gear ratio.