NC21/NC24 Differences

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bantam_dave21
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NC21/NC24 Differences

Post by bantam_dave21 » Mon Aug 02, 2010 11:29 pm

Hi All,

no doubt the answer to this i here somewhere I just can't find it and I've been at it a while now.

What are the main differences between the NC21/24 other than the swingarm obviously. For instance like mine with the swingarm conversion is it now essentially an NC24. I saw Neo wrote somewhere (I think anyway, its been a long night) everything is interchangeable between 21 & 24. Are front forks, wheels and brakes the same? similarly do they use the same motor with subtle jetting differences?

If anyone ca throw any light on it - would be mass appreciated, will help loads when something for sale is badged as NC24 handy to know which bits will and won't go backwards to the 21.

Thanks

Dave

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Re: NC21/NC24 Differences

Post by Cammo » Tue Aug 03, 2010 12:19 am

Neo should be along soon to answer your queries! :peace:
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Re: NC21/NC24 Differences

Post by CMSMJ1 » Tue Aug 03, 2010 10:17 am

Apart from some exhaust, bodywork and swingarm they are the smae animal I reckon and all parts can be swapped between them.

As it happens...Neo will be along...he always is! 8-)
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Re: NC21/NC24 Differences

Post by Neosophist » Tue Aug 03, 2010 10:52 am

The frames are the same (apart from the frame numbers!) so all the drillings are present.

The NC21 has a hyrdaulic clutch, this needs the matching sprocket cover and pushrod, as well as some longer bolts for the sprocket cover, like wise, if your fitting the NC24 cable clutch you'll need the sprocket cover and shorter bolts.

Collectorbox is differnet between the two as the 21 has a low-level exhaust.

The 24 subframe has a hanger for the rear exhaust and uses different rear-pegs.

The NC21 has a different Reg/Rec but same connector.

There are subtle differences between the wiring looms too, some of the plugs are different shapes.

The NC21 has a twin piston rear-caliper, the NC24 has a single piston rear caliper.

The NC21 has fixed discs the NC24 has floating discs.

Internally, the NC24 had revised camshaft profiles, you'll notice that a lot of the parts end in 720, as opposed to 000 of the NC21, indicating a revision.

The clutches are different, the NC24 basket is the same part used on the NC30, I theorise that you could drop an NC30 internal in there (yet to test this)

Depending on your NC21 there were two clutch baskets fitted, the plates are the same so i'm not sure what the changes were.

Generators are different, the NC21 uses a smaller genny and flywheel ,some early NC24's use the smaller genny too, i'd stick with the later 350watt type across all models if you need to change it, though this might require the later-type flywheel.

An interesting point here is that the only flywheel available for the NC24 is the MR8 NC30/35 version. The NC21 still has listed the old ML0 type, although I can't see a problem fitting it as the genny covers are the same between both models so it'd fit.

The carbs have different jetting / internals between the models. The NC24 has the richest jetting (115's), the NC24 came with two revisions of the slides. After / Before VDE-2F, the NC21 has different slides to both, along with different needles too.

The fork internals are different, springs have different rates, the NC24 has air adjustable valves while the NC21 doesn't.

Likewise the rear shocks have different internals / springs.

There are differences internally between the gearbox too, I think the affects the ratios too, I'm at work at the moment and dont' have the information to hand.

If you think of the NC24 as a refined NC21 you should get the idea, things were smoothed out / improved over the 21.

Most things will bolt straight in, but if your going for engine work it's best to stick to the 21 stuff for a 21 engine or vice-versa when it comes to gearbox parts, carbs / cams. Chopping and chaning might lead to some really weird running engine.

Expansion bottles differ.

Pistons / Crankshaft / are different between the models.. NC21 has KT8 PCN's in there (I'm sure KT8 is a CBR400 Aero), NC24 has two revisions of piston depeding on year.. but there both ML0 and end in 720 / 721

Interestingly though the rods are the same.

There all NC13E engines anyway, even in the later 30 / 35. I can't see why you could transfer a 30 internals to a 24 case (you'd get a nifty oil cooler too).

Obviously if you went major like this all the bearing shells, cam journals etc would need to be re-checked. Major work and not for the feint hearted.

But I would't chop and change cranks without pistons etc.

However, If theres anything your thinking of fitting and are unsure just ask :-) I'm at work at the moment and will have more info later.
xivlia wrote:i dont go fast on this bike so really do not need a rear brake.. /
vic-vtrvfr wrote:Ask xivlia for help, he's tackled just about every problem u could think of...

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Re: NC21/NC24 Differences

Post by bantam_dave21 » Tue Aug 03, 2010 1:38 pm

Neo - thanks, quite a list.

Tho you have brought to my attention a good few bits of great interest.

It would appear my bike is quite a mash up lol. If the 24 forks are air adjustable, and floating discs I would say my 21 has had a transplant. Which is good I think, I don't know if the 21 did but these forks have what I would guess at an anti dive system? Floating discs, which I think are cheaper than solids so all good.

I would guess at my enigne still being original tho (admittedly I haven't got it out yet or seen the number) but all the jet sizes you gave me previously are massively indicative of it being set up like a 21 at least.

Also, only a guess at the moment, but i think when its had its swing arm conversion its probably had a sub frame mod change too? as my exhaust is at high level which looks to be mounted as you would expect as the 21 was a low silencer about the height of the swingarm? With thae comment about silencer difference would it be a reasonable guess that the collectorbox/downpipe set up is that of a 24? quite an undertaking tho just for a high level exhaust? But handy to know when it comes to new shiny aftermarket can time.

Thanks Again

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Re: NC21/NC24 Differences

Post by Neosophist » Tue Aug 03, 2010 2:29 pm

What is your frame number (don't need the last 2 digits)

Any pictures of the bike?

Does it have a cable or hydraulic clutch? They all have anti-dive on them.

Floating discs are usually more expensive.

RE: Subframe.

Does your exhaust bolt to the footpegs or a hanger thats welded to the subframe?

If you put up pictures i'll tell you.
xivlia wrote:i dont go fast on this bike so really do not need a rear brake.. /
vic-vtrvfr wrote:Ask xivlia for help, he's tackled just about every problem u could think of...

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Re: NC21/NC24 Differences

Post by bantam_dave21 » Tue Aug 03, 2010 2:49 pm

Well thats another interesting bit as its cable clutch, or at least cable at the clutch lever unless, its cable over hydraulic? I've not got that far in the strip down yet. I'm assuming hydraulic clutch is a master at the bars?
The forks deffo have air valves at the top.
I have no rear pegs as yet so I'm think it direct to a sub frame bracket.
I've not shopped around much for discs as yet, but these are floating (ie on buttons - if thats the correct term)

Its very bare at the minute, only engine, swing arm, frame @ wheels.

But i'll try sit the sub on it later for a few pics, along with frame number

Thanks
Dave

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Re: NC21/NC24 Differences

Post by Neosophist » Tue Aug 03, 2010 3:17 pm

It sounds like an NC24.

The NC21 has a master cylinder at the bars for the clutch too.

Is the brake resevoir seperate from the master cylinder or integrated?

The NC21 has Silver matching brake and clutch cylinders in this style

Image

The NC24 has a cable clutch and a floating resevoir like this

Image
xivlia wrote:i dont go fast on this bike so really do not need a rear brake.. /
vic-vtrvfr wrote:Ask xivlia for help, he's tackled just about every problem u could think of...

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Re: NC21/NC24 Differences

Post by bantam_dave21 » Tue Aug 03, 2010 3:29 pm

Only the second picture is showing Neo - probably the stupid PC in my office, I'll try view again when I get home.

Mine front brake master looks as shown in second pic, slightly remote with short feed hose from reservoir to master. My clutch is deffo cable fitting at the bar, as I disconnected it last night - deffo a conventional cable & nipple end.

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Re: NC21/NC24 Differences

Post by Neosophist » Tue Aug 03, 2010 4:07 pm

It sounds like an NC24 to me.

NC24 forks / brakes / swining arm / clutch.


If you give me the engine number i'll tell you what its out of.
xivlia wrote:i dont go fast on this bike so really do not need a rear brake.. /
vic-vtrvfr wrote:Ask xivlia for help, he's tackled just about every problem u could think of...


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