1987 GPX (ninja) 750R. It has tons of get up and
hi,this might help,you will have to remove the carbs to do it,but check the float levels in the carbs,it sounds like it is not getting enough fuel when the load goes on,the engine is using more fuel under load and the carbs cant keep up,while you have them apart give them a good clean out,make sure all the jets are nice and clean,also have a look at the air filter ,a blocked or dirty air filter will also affect top end or"under load"performance,before i forget,when you had the fuel tap apart did you make sure that the gauze filters on the petcock were nice and clean,if they are just slightly dirty they will also affect performance.if the bike has a vacuum pump on the fuel tap,check that the vacuum line from the pump to the pickup point(normally the intake manifold or a point on the vacuum side of the carbs,ie engine side)is in good condition with no kinks or cracks,if it has a kink in the line it will not create enough vacuum to run the pump,causing poor fuel flow under load,i have just done a repair on an 89 gsxr 750 slingshot that the owner has spent a fortune on trying to get it right,and it turned out to be a $4.00 kinked vacuum line to the fuel pump...hope this helps...cheers