I honestly think that is your best course of action, Felix.

As for the air correction, yes I believe the MC21 and MC28 share the same solenoid setup, but the X and Y-pieces are "tuned" to the particular application, so particularly, if you are retaining the airbox, you would be wise to fit the MC21 Y-piece. We have actually mixed MC18, MC21, and MC28 X & Y-pieces, and MC18 & MC21 emulsion tubes to fine tune MC21 fuelling in the past, but that's starting to get really technical and fussy!

If you check the Stock NSR250R Jetting page in the Workshop Section of the main site, you will see there is a large variance between the MC28 and MC21 [and MC18] base settings. As I said previously, the MC28 carbs could be made to work with time and patience, but there is no starting point I can give you or recommend, and honestly believe the MC28 TB type carbs are actually a step backwards performance-wise from the TA series, particularly for a derestricted bike.

While the crankcases, crankshaft, barrels, and heads are essentially the same between MC21 & NMC28, the MC28 ignition is significantly different [as you already noted], and both the airbox and exhausts (both chambers and silencers) are substantially more restrictive. Also, the way the PGM-IV controls the air correction differs significantly to previous models. While the setup works extremely well for a standard MC28 in road trim, and it unquestionable the most refined & smoothest of all NSRs to ride in standard form, its fuelling requirements are very different fuelling to that of the MC21.
_________________
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.

Check us out on Facebook! Please "like" our page!