{"product_id":"akrapovic-optional-header-stainless-kawasaki-ninja-400-500-z400-e-k4r2","title":"Akrapovic Optional Header Stainless Steel Kawasaki Ninja 400 \/ 500 \/ Z400 (2018-2026) – E-K4R2","description":"\u003cp\u003eFive point two horsepower on a 44 PS motorcycle. That is nearly twelve per cent, and it is the largest relative power gain of any header in this catalogue — because a small Kawasaki twin loses more to its emissions equipment, proportionally, than a big engine ever does.\u003c\/p\u003e\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e49.5 PS with the matching slip-on, from a standard 44.3\u003c\/li\u003e\n\u003cli\u003e38 Nm, gaining 3.4 measured at 9,300 rpm\u003c\/li\u003e\n\u003cli\u003e1.59 kg where the standard header assembly weighs 4.08\u003c\/li\u003e\n\u003cli\u003eStainless steel throughout\u003c\/li\u003e\n\u003cli\u003eStatic noise of 98.9 dB against a standard 86.6\u003c\/li\u003e\n\u003cli\u003eAn hour of workshop time\u003c\/li\u003e\n\u003cli\u003eClosed course competition use only\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eTwelve Per Cent\u003c\/h2\u003e\n\u003cp\u003e44.3 PS to 49.5. On a litre bike five horsepower is a rounding error; on an A2 machine it is a different motorcycle out of a corner. Kawasaki's standard header carries a large catalytic converter sized for Euro 5 on a 399 cc twin, and taking it out is where nearly all of this comes from.\u003c\/p\u003e\n\u003cp\u003eTorque follows the same pattern: 35.8 Nm to 38, with the gain read at 9,300 rpm.\u003c\/p\u003e\n\u003ch2\u003eTwo and a Half Kilograms\u003c\/h2\u003e\n\u003cp\u003e4.08 kg down to 1.59. That is 61 per cent, and on a motorcycle of about 168 kg it is a meaningful fraction — taken from the lowest and most forward point of the chassis, under the engine.\u003c\/p\u003e\n\u003cp\u003eOn a small twin used for club racing or track days, weight in that position is worth more than the same number bolted anywhere else.\u003c\/p\u003e\n\u003ch2\u003eTwelve Decibels Is the Price\u003c\/h2\u003e\n\u003cp\u003e86.6 dB standard to 98.9 at 5,000 rpm. Kawasaki builds these bikes quiet, and this header undoes that comprehensively. Circuits with a 95 dB static limit will refuse it, and no insert is offered to bring it back down.\u003c\/p\u003e\n\u003cp\u003eThat figure, more than the approval status, is what decides whether a given rider can use this part.\u003c\/p\u003e\n\u003ch2\u003eIt Needs the Slip-On\u003c\/h2\u003e\n\u003cp\u003eAkrapovic builds this header as an upgrade path for machines that already wear the Slip-On Line. Bolted to Kawasaki's standard silencer it has nothing sensible to work with, and the published figures assume the pair.\u003c\/p\u003e\n\u003ch2\u003eThree Names, Nine Model Years\u003c\/h2\u003e\n\u003cp\u003eKawasaki's 399 cc twin powered the Ninja 400 and the naked Z400 from 2018, and the 451 cc Ninja 500 replaced the 400 for 2024. The exhaust route did not change, so one header covers all of them.\u003c\/p\u003e\n\u003cp\u003eThat is unusually broad coverage for a performance part and it makes the Ninja 400 platform one of the easier small bikes to build up.\u003c\/p\u003e\n\u003ch2\u003eAn Hour\u003c\/h2\u003e\n\u003cp\u003eSixty minutes of workshop time. A small twin has two header pipes rather than four, and there is little in the way, so the job is straightforward once the fairing is off.\u003c\/p\u003e\n\u003ch2\u003eRoad Approval\u003c\/h2\u003e\n\u003cp\u003eNone. This product does not meet emission compliance requirements for street or highway use.\u003c\/p\u003e\n\u003ch2\u003eSpecifications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003ePart number: E-K4R2\u003c\/li\u003e\n\u003cli\u003eEAN: 3831126413156\u003c\/li\u003e\n\u003cli\u003eBikes covered: Kawasaki Ninja 400, Ninja 500 and Z400, 2018 to 2026\u003c\/li\u003e\n\u003cli\u003eType: optional header, for use with the Akrapovic Slip-On Line\u003c\/li\u003e\n\u003cli\u003eMade of: stainless steel\u003c\/li\u003e\n\u003cli\u003eWeight: 1.59 kg against 4.08 kg standard\u003c\/li\u003e\n\u003cli\u003ePower: up to 49.5 PS from 44.3 standard; 5 PS more at 9,550 rpm\u003c\/li\u003e\n\u003cli\u003eTorque: up to 38 Nm from 35.8 standard; 3.4 Nm more at 9,300 rpm\u003c\/li\u003e\n\u003cli\u003eNoise: 98.9 dB against 86.6 standard, measured at 5,000 rpm\u003c\/li\u003e\n\u003cli\u003eWorkshop time: about an hour\u003c\/li\u003e\n\u003cli\u003eApproval: none; closed circuits only\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Akrapovic","offers":[{"title":"Default Title","offer_id":53629422272778,"sku":"E-K4R2","price":339.15,"currency_code":"EUR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0949\/7831\/0410\/files\/01_2f07637f-0d63-4c5c-b145-c0b91467805a.png?v=1788563025","url":"https:\/\/inter-pace.com\/en-it\/products\/akrapovic-optional-header-stainless-kawasaki-ninja-400-500-z400-e-k4r2","provider":"Inter-Pace","version":"1.0","type":"link"}