I have an 86 GSXR GK71F and it tops out at 175-180KPH but feels like it should have more. It stops at 10k RPM in top and at 11K in 5th. Does anybody know how this bike is restricted? It already has performance ignition system fitted. Thanks guys. Ben.

Hi,
Not 100% sure of restrictions on the earlier gixer but look if there is a gear sensor on the left side of the engine (just by the front sprocket), its got two wires that go to the cdi (oh sorry carnt call it a cdi) tpi, one is black or maybe blue (neutral) the other will be green /yellow. You need to undo the green/y wire then using a 1.5K ohm resistor make a connection wire that connects the tpi side thrugh the wire and then to ground, you leave the gears ensor side loose. This resistor will trick the bike into thinking it is always in 2nd gear so no 180Km restriction is switched. If no gear sensor then must be in the clocks (remove speedo cable and see if it pulls higher) Honda use the speedo trick but Suzi usually use the gears.

OK, since the original post i have fitted a MPH speedo convertor and this made no difference at all. There are 3 wires from the left hand side cover to the ignition module under the seat. They are Brown, Black with White trace and Green with White trace. What do i need to disconnect and what needs earthing through the resistor?

Are we looking in the same place? not from the sidecover but from a sensor on the end of the gear box shaft, very close to the front sprocket and gear lever.

There is a plastic coated wire exiting vertically downwards under the sprocket cover but it's very hard to get at an i cant see where it leads in the dark. This is the only other wire i can see, Could this be what you're looking at? Thanks, Ben

Between the sprocket,water pump and gear linkage will be a small plastic sensor with two screws that has wires going up to near the battery. If it is using this for restriction ther will be a green/yellow wire + the neutral wire connected to the cdi and the green/yellow is used to tell the cdi wot gear the bike is in using different resistances for each gear.