Hi NSR quys!
Which carburetor do you believe is the best for performance for a trackbike?
I have both carbs mc28 and mc21 with HRC kit and i dont know which i will use on my project bike for track use.
My impression when i look carefully the two carbs is that the mc28 has a better velocity stack and i like them more from the mc21 carbs but i dont test them both to have a good opinion and i dont know what to use for my track bike.
If someone has done some tests with both carbs i would love to hear his results.

I've never run them back to back but the MC21 carb is much better to work with. Much better for ease of setting up.
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If I have to take the carbs off once more...

Hi
Thanks for your reply.
Why the mc21 carbs are easier to setting up?For me they look same.
But for the velocity stack of the mc28 carbs which are absolutely round and they have and a shorter air intake distance and you can bore them to 33,5mm much more easier from the mc21's what is your opinion?
I have never saw a velocity stack with the same shape as the mc21 carbs on any other race bike,only the nsr f III.
I am a little comfused i dont know what carbs will work better.

I never bored my MC21 F3 carbs and it went very well.

You try changing the needle position on a set of '28 carbs compared to a '21. You'll soon decide to run '21 crabs. They are much nicer to work with.

As with most things on a '28 they seem to be a step backwards. They do look like nice little carb though.
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If I have to take the carbs off once more...

I run mc21 electricals with pgmIII and hrc derestrictor on my bike so it is one more reason to work it and with the mc21 carbs,but i will test and the mc28 carbs from curiosity.
Did you test the mc28 carbs on your bike with no other modifications on the engines performance to tell me your results?

StephenRC45 wrote:I've never run them back to back but the MC21 carb is much better to work with. Much better for ease of setting up.

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If I have to take the carbs off once more...

ok

Why not try MC18 cabs, wonderful performance...

Also need MC18 cylinder set would be well..
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1996 HONDA RS250
1995 MC28 NSR250 SE red/white/green
1994 MC28 NSR250 sp W/ RS250 engine

The '18 carbs are almost identical to the later '21's.

I've run '18 carbs on '21's and there isn't anything in it.

'18 cylinders are better than '21/28 barrels port wise as stock though. '18 have a little more mid range and more top end. The boost port is better on the '18 and the exhaust port window is more performance orientated.

Of course the '21's can be modified to equal it.
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If I have to take the carbs off once more...

The carbs from mc21 which i will use they have this code on them TA22B(A)GC1
do you know what model are they and if they have any differences?

Have a look here

http://tech.nsr-world.com/nsr/nsr-all/carb-settings/
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If I have to take the carbs off once more...

They have different settings at the jets and needles from the factory,i have for my carbs an HRC jet kit so i will not use the oem but does anyone noticed any difference in slides or in the cases of the earlly and late carbs which will affect the performance?

Serious question, what are you really hoping to gain? What have you done to the rest of the motor.

At the moment, it all looks like a lot of fuss over nothing. The MC18 and MC21 carbs are far easier to work on, as Stephen has commented, and you have a set already kitted with HRC parts.

While one setup may ultimately be better than the other on the dyno, I doubt the difference will be consistently measurable, and certainly not noticeable... until you try and adjust the needles, that is!

The whole of the MC28 was geared towards being a more refined street bike.
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Andy.
NSR-WORLD.COM

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Hello Andy
I have done many tunings in the motor so thats why i am searching everything details if i can get some more power.
The bike is mc28 and the tunings are:

wiring loom and pgmIII from mc21 with HRC deristrictor
spark plugs and caps from rs250
rear head conversion with squish setting to 1,0mm
HRC intake rectifiers
HRC NF5 reeds
HRC carb jet kit
JHA exhausts the model who fits only the mc28 swingarm
crankcase flow tuning and matching to the cylinders
cylinders porting
and finally i will work it in Avgas or VP high octane fuel.

I have the HRC kit for mc21 carbs only from luck,it was the only available that i could find if i could find and an mc28 jet kit i would buy it just from curiosity to test both the carbs.
I did some measures before some hours to both carbs 21/28 and i notice that they are bigger in the backside so i am happy that i have an hrc kit for the mc21 carbs because and people with many NSR knowledges like you and Stephen suggest me to work my bike with mc21 carbs!
I have and a post on HRC nsr250 section Andy if you dont mind take a look at the question which i have for a code
thanks for all replies

I remember that mc28 carbs have a smaller overall length which is good for top end performance and in conjunction with the shorter mc28 manifolds should give a better throttle response.
mc21 carbs are D-bored which I really like but performance over a standard round bore is questionable.
mc28 needle holder sucks but I believe that it can be swapped with the mc21 one.

That said, if you only have a HRC kit for the mc21 carbs, I can't see what's the point of comparing between them.
Obviously, the mc21 carbs are the way to go.
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2t-racelab.com