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Exhaust conversion for MC21 NSR250


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Exhaust conversion for MC21 NSR250

Fri Jul 02, 2004 4:35 am » Post: #1 » Download Post

I'm wondering if it's possible to use the 600RR undertail exhaust on the MC21? If not, are there any undertail exhaust kits on the market?
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Andy
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Fri Jul 02, 2004 8:19 am » Post: #2 » Download Post

It's not possible to use any part of the CBR600RR exhaust system, or that of any other 4-stroke, as the "workings" of the two types of system are completely different.

There are, as of yet, no aftermarket under-seat exhaust systems for the NSR.

The main problem with bringing an exhaust up under the seat is the routing of the pipe. The 2-stroke expansion chamber shape and length are critical to peak performance and it's just not practical to chop and change what works perfectly for something that just looks good!

The idea has been looked at before though. Matt from TYGA Performance and I looked closely at the possibility of turning one cylinder 180º, but the exhaust manifold then runs straight into the crankcase! There is just no way to make it work. The only other way I could think of doing it was to modify a CR125 pipe (or similar) and routing the exhaust in behind the fairing like a Yamaha TDR250, but the MX bikes have a completely different chamber size and shape for totally different power output characteristics! Put simply, it ain't never gonna' happen!!!! :)

Andy.
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Dave Ett
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Fri Jul 02, 2004 8:20 am » Post: #3 » Download Post

No. A two stroke needs an expansion chamber to use the pulses from the exhaust to scavenge the cylinder and stuff gases back in as they try to escape at high revs.

This chamber needs to be a certain distance from the exhaust port, which is why the V twin seems to have unequal length pipes.

You could run the exit pipe from the expansion chamber up under the seat and into a single silencer I'm sure, but I think it would look damned odd!
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