Hi I have a question regarding the exhaust diameter for my CBR F2.

I used to have a Devil exhaust slip on but after a few years the 2 into 1 part of the headers had a hole because if rust and I had it replaced and got a new slip on.

The company that did the work inserted a new section in the 2 into 1. The old diameter was 55mm but the new diameter stainless pipe is 50.8mm. My mid range power is all but gone and the general power of the bike feels more like a 400 than a 600.

The day I fetch the bike after they inserted the new section and new slip on the bike couldnt idle without the choke being open. The company adjusted the idling screw and that sorted out the idling but I am afraid that was the start of my problems...

What is the correct diameter pipe? Do I just need to re jet the carburetors?

I appreciate any feedback.

Thanks

 

Ok, since you already stated "The old diameter was 55mm", I'm thinking you might need to clarify exactly which diameter you're unsure of, and, are you talking about inside diameter or outside diameter?
If your bike was running fine until this change, then your're correct, that's a pretty good indication that this exhaust issue is the culprit, but I will confirm - yes, you mess with the header pipe's diameters at any stage from the head to the mid-pipe, and it will throw your engine's performance off.