HI All

Another question, I am thinking of buying the stainless tyga exhausts from jap 4 performance but believe i will have to change the jets in the carbs? i know we need certain amount of stoichiometric air per kg of fuel burnt etc but surely if the outlet diameter of the exhausts are the same as the standard ones then we should not need to change them? or is it because of the smooth finish on the inside of the expansion pipes allowing exhuast gases to pass more freely allowing more air in hence changing the jets for amount of fuel? Also does anyone know what size jet would be needed if need to do and where i can get them? Thanks.

Ian

Ian

With the greatest of resoect, Ian, your post is exactly why I do not allow jetting discussion on the public forums.

There are many variables, including, but certainly not limited to, air density, air temperature & humidty, fuel type, ignition, and compression. Spark plug type, even manufacturer, can affect jetting, as can different air cleaners. That's before you even consider the expansion chamber type and make... yes, changing from a set of Jha chambers to a set of TYGAs can even necessitate a change of jetting, let alone changing from a stock set. Just changing the silencers to a set of Swarbricks or similar can make a difference.

TYGA will probably give you a baseline setting, but every bike is different. You cannot even take two MC28s with the same specification and guarantee that they need the same jetting. Yes, all stock NSRs (like-for-like) use the same settings, but factory settings, both jetting and ignition, are very safe. (Standard motors are effectively detuned by approx. 30%.)

TL:DR

Many years ago, on the previous incarnation of this forum, someone posted their MC21 settings for someone else. Their motor subsequently seized, and they tried to hold me responsible "for allowing/hosting the information". Yes, those kind of people exist, and for that reason I do not allow jetting discussion here.
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Andy.
NSR-WORLD.COM

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Hi Andy

Thanks for the info, I do completely agree. Maybe i will have to trial and error. Also shame those people exist, your just trying to help. All the best.

Yeah, sorry about that. But once bitten, twice shy I'm afraid.

As I say, I believe TYGA will give you baseline setting, trying their best to account for your personal state of tune, other than that I can only direct you to either the standard NSR carb settings, or the HRC baseline settings which, in reality are very little use to anyone! I've never personally seen either MC21 or MC28 HRC base settings work particularly well.

There is also a basic summary/guide by Aktive at the bottom of the page here: https://www.nsr-world.com/tuning/250-tuning/carburation-index/jetting/
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

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Thats great info cheers Andy.