Header diameter increases

[T250]

I've got some Black Widow headers but managed to get hold of some original chrome ones for my K2, the reason being purely for aesthetics the aftermarket pipes discoloured very quickly and looked tat, can't say I noticed any difference in performance, but I am an old fart and don't push on too hard these days...

[grog]

T250, no good to me if they discolour, I'll forget about that idea. Thanks

[gsxbarmy]

T250, no good to me if they discolour, I'll forget about that idea. Thanks

Having no inner pipe @grog they will "bronze" almost immediately, probably most of the way down the header as well.

[Ade]

I cut one of the standard header pipes open to measure. They are 42mm OD but the inner tube is 28mm OD giving a bore of 25mm. I wanted a lighter single skin header set, Delkevic, Black Widow and Lextek all make single skin stainless header sets with 40mm OD tube. Delkevic and Lextek use 1.5mm wall tube giving 37mm ID. Black Widow use 1mm wall tube giving an ID of 38mm. Delkevic and Black Widow sell the headers on their own, you have to choose which link pipes you want. I went for the Lextek ones because they have a lifetime guarantee and come with the two link pipes included, plus they are cheaper than the others, it was £185 all in. The others were £250 for Black Widow headers and £280 for Delkevic, then you add on the price of the link pipes. That was early 2026, don't know if they have changed pricing.