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Spare jets found..


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Enessr

 
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Spare jets found..

Sat May 02, 2026 8:49 am » Post: #1 » Download Post

Ok,
I unearthed a small packet of spare main jets buried amongst
a load of bags of spares for both the rgv and nsr..
1x 145 and 1x 150, both for the nsr carb.
My question regards the fitting of the bigger jets, on the
Rgv it's easy as both carbs are separate units compared to
the nsr.
Which carb. side feeds the top cylinder on the nsr?
The top cylinder requires the bigger jet I assume as it's covered
so which side of the carb gets the larger fuel jet?
The mods done so far are straight plug heads, wire splice (only or/bl
wire) modified stuffers with o.e reeds full carbon tyga airbox
and original mc21 full exhausts.
Cheers
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Andy
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1991 Honda NSR250 MC21
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Sat May 02, 2026 10:12 am » Post: #2 » Download Post

The MC21 front (lower) cylinder is enriched by means of a larger power jet. (#75 vs. #72)

Carb orientation as per our Honda approved English Service Manual.



The carbs are easily removed as a compound assembly, with the removal of the two clamps securing them to the manifold. Disconnect the TPS, but you don't need to disconnect the throttle or oil pump cables. There's just enough room to turn the carbs to get the float bowls off and change jets. Once you've done it a couple of times, it's a very quick procedure.

Please see the stock jetting page in the Workshop section for standard settings, and the HRC base settings in the Carb Tuning section of the Main Site.

I'm afraid we do not allow specific jetting discussion in the public forums for reasons mentioned numerous times.
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Enessr

 
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Sat May 02, 2026 4:41 pm » Post: #3 » Download Post

As usual Andy, THANKS!
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Andy
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1991 Honda NSR250 MC21
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Sat May 02, 2026 6:30 pm » Post: #4 » Download Post

If you have one... and if you haven't, invest in one... use a proper Japanese JIS screwdriver on the float bowl screws!

JIS screws are indicated by a little dot on them.


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Andy.
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