What is likely to be more powerful?
-MC28 with HRC keycard, and (HRC or JHA) chambers, JHA endcans, stock jetting.
-MC21 with same chambers/cans and the wire splice.

I ran my MC28 -as described- last racing season and it never needed any maintenance, and seemed more powerful than I would expect from such basic derestriction. I bought an MC21 with an RS250 engine, but have decided it's just going to be way too much trouble and expense on maintenance. So I am thinking I might sell the RS250 engine and buy an NSR engine for the MC21, or just go back to running the trusty MC28.

Advice?

Also I am completely clueless as to what is on the MC21 at the moment with the RS250 engine in terms of electrics and stuff. The ECU doesn't look like a PGMIV or PGMIII unit. What about putting MC28 engine/electrics into the MC21, would that be just as easy, or are there major differences?

J
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MC28 SE -sold-
MC21 with RS250 engine -for sale-
MC21 race bike -soon for sale-

It's generally acknowledged that the 21 is a faster bike as it's less restricted, and those restrictions are easier to remove. However, that's for the road, and will the full race prep done I guess the 28 won't be far behind.

What power are you getting from the 28?

Have you modded the suspension?

Have you lightened it?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

I need to dyno the MC28 to finnd out the power, but I was surprised at the difference, which was much more than I expected from reading the forum and checking all the various pages on the internet. The front comes up just rolling on the throttle at 9,000rpm. Also I meet a great deal of other NSRs at the track and I don't know if it's my imagination, but I'm sure I pull faster out of the corners ... maybe I'm just keeping it in the powerband better. Only a dyno can tell.

The suspension was overhauled but not modded. This year I'm putting an RS250 complete front end on it, steering damper, and going to magnesium wheels, plus getting the suspension measured, overhauled and set up by a racing suspension guru. I'm not aiming to be competitve. Haven't really lightened it, except it's got race bodywork/tank (read tatty), and all the lights, mirrors are removed.

To go fast, I don't need ever further-refined engine mod.s, I need tip top suspension/brakes, properly set up, and lots of training.

If I am tempted to get competitive, then I'll either go to the 600 class (might do some team racing on a CBR600RR this year), or GPmono, which is a relatively new class in Japan: RS125 frame with 4-stroke engine.
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MC28 SE -sold-
MC21 with RS250 engine -for sale-
MC21 race bike -soon for sale-

Ah! Forget it. I've just decided it would be waaay too much trouble to put the MC21 back to NSR status, it's got RS250 tank, bodywork, airbox, etc.. I'd probably have to change the rear frame.

So I'm going to sell it complete ... see the classifieds section!
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MC28 SE -sold-
MC21 with RS250 engine -for sale-
MC21 race bike -soon for sale-