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you will have to open the carburettor and check whats the size of the main jet running???

hi

Hey...the Fz runs a 112.5 main jet. I did try using a couple of oversize jets like 115 ,117.5 and 120. The bike runs great with size 117.5 in initial revs, but develops either a flat spot or a fuel surge phenomenon when pulled hard. I have not yet been able to understand this fully and am working on it. I tried removing the air filter element too, but to no use. Now, fixing a K&N may worsen that problem if you upsize. Also, you might have to remove the stock airbox and intake pipe to mount a K&N on the carburettor. Be careful with the small resonator box on the intake pipe...it kinda comes off easily.

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Crankpin,
I'm also facing same problem. I was looking around to solve this and found out 2 things.
1.. It is due to the TPS found somewhere on internet and can be solved by reseting it.
2.. Secondly it seems it can be also cause due incorrect float setting or use of stock exhaust as incorrect float setting will cause low amount of fuel in carb bowl. since we have upjetted fuel gets exhaused faster and a surge is developed at a lower limit than stock.
and stock exhaust restricts smooth flowing of exhaust and at higher rpm exhaust dont escape out effectively. It is just like you put something infront of your exhaust outlet and engine doesnot revs effectively.


But its just a conclusion after going through various articles on internet. I'm not a mechanic or an engineer so i am not sure.
By the way i'm using high lift cam shaft and 115 size main jet.

I'm posting you all a link which i think would be usefull for you all.
And remember one thing that without a free flow exhaust you won't get a good respone which is desired by we all from our tweaked up engine.


CV Carb Tuning Procedures