What exhaust header size to go for

Hello to one and all!

Longtime lurker and first time poster. I've had my Ace for about a year now and have just started to do a load of mods that have been on my mind for awhile. I'm having a custom header made at a local exhaust shop, as the OOracing one is out of stock for the next month or two.

The shop has quoted me a very reasonable price but they can only get either 38mm or 32mm stainless steel as opposed to the 36mm of the OO header.

So just wondering what those more technically minded than myself would recommend. Im guessing that it would alter where torque is available in the rev range but any other effects? On the intake side I have the prejetted Molkt carb with pod filter available from OOracing.

Thanks in advance for any suggestions

Cheers

Oh also forgot to ask, has anyone got a kickstart lever that they would be willing to sell? Mine was lost in transit by the dealer!

Welcome aboard!

Pipe length is as important as diameter in optimising performance.
The exhaust on my bike is designed for upper midrange. The header ID is 1" (25+mm) and longer than standard.
The brackets for the muffler were changed and a rear support was fabricated. The muffler has been de-restricted to flow more freely.

Keep us posted (with photos!)

Crazy

red, where do you live? I have a spare.

Also can anyone tell me how they go about measuring/creating the optimum back pressure with their exhaust pipe?
I am using a full length OORacing pipe at the moment, should it be fine?

Hello sorry just got back from london for the weekend! Im based in Worcester in the uk

Thanks for the info crazy, yours looks very smart on the bike.

The SS pipe is 1.5mm thick so my choices are 35mm or 29mm internal diameter, if anyone has any recommendations. I have looked at Sonreirs posts about exhaust calculations but was wondering if anyone had some real world experience of diameter effects on the Ace.

Oh, I would also just like to say how helpful and interesting this forum has been since I bought the Ace so thanks to everyone in the community!

The 29mm would give higher gas velocity and provide better power at usable revs.

Sonreir's calculations give a good indication of the sort of exhaust you need.

Crazy