NC21 EARLY AND LATE ENGINES CAN THEY BE SWOPED

[mrsheerline]

NOT MANY PEOPLE KNOW THAT THERE IS A MK 1 AND MK 2 NC21 THE ENGINES WERE SLIGHTLY DIFFERENT, THE CDI BOX ON THE EARLY ONE WAS LOADS BIGGER AND DOES NOT REV AS HIGH AND DOES NOT HAVE AS MUCH POWER THE INTERNALS ARE DIFFERENT AS WELL, WHAT I WANT TO KNOW IS WILL THE ENGINES SWOP OVER OR DO WE THINK THAT THE SAME CDI AND LOOM MUST MATCH THE RIGHT ENGINE, ACTULLY THE MORE I THINK ABOUT IT I THINK THEY MUST MATCH THE RIGHT ENGINE IT MUST BE TO DO WITH THE IGNITION TIMMING AND ADVACE CURVE,

WOULD LIKE TO NO OTHER OPPINIONS

[Cammo]

Are you referring to the two models being vfr400z (naked) and vfr400r (faired)? I really doubt the engines were different, particularly the internals. Why do you think they're different?

Anyway, pretty sure it won't matter the parts will swap between them fine.

This link shows all nc21 models (and 24 paint schemes): http://www.vsource.org/VFR-RVF_files/Bv ... -rj-mi.htm

[mrsheerline]

Are you referring to the two models being vfr400z (naked) and vfr400r (faired)? I really doubt the engines were different, particularly the internals. Why do you think they're different?

Anyway, pretty sure it won't matter the parts will swap between them fine.

This link shows all nc21 models (and 24 paint schemes): http://www.vsource.org/VFR-RVF_files/Bv ... -rj-mi.htm

THE LATE NC21 HAD THE SAME ENGINE AS THE NC24, BUT NOT THE EARLY NC21 AND THERE IS DIFFERENCES

[mrsheerline]

YES THAT DOES SHOW THE DIFFERENT MODELS, THE NC21 DEPENDING ON YEAR HAD EITHER THE LATTER NC24 ENGINE OR THE EARLY NC21 ENGINE HOW I NO THIS I HAVE TWO NC21 WITH THE TWO TYPES OF ENGINE AND THE LATTER ENGINE IS [BETTER NC24]

[Cammo]

HOW I NO THIS I HAVE TWO NC21 WITH THE TWO TYPES OF ENGINE AND THE LATTER ENGINE IS [BETTER NC24]

You might want to check the engines are original, engine numbers for the nc21 and nc24 can be found here: http://www.400greybike.com/files/models.htm

[CMSMJ1]

STOP FECKING SHOUTING PLEASE.

CAPS LOCK can work both ways

[Neosophist]

NOT MANY PEOPLE KNOW THAT THERE IS A MK 1 AND MK 2 NC21 THE ENGINES WERE SLIGHTLY DIFFERENT, THE CDI BOX ON THE EARLY ONE WAS LOADS BIGGER AND DOES NOT REV AS HIGH AND DOES NOT HAVE AS MUCH POWER THE INTERNALS ARE DIFFERENT AS WELL, WHAT I WANT TO KNOW IS WILL THE ENGINES SWOP OVER OR DO WE THINK THAT THE SAME CDI AND LOOM MUST MATCH THE RIGHT ENGINE, ACTULLY THE MORE I THINK ABOUT IT I THINK THEY MUST MATCH THE RIGHT ENGINE IT MUST BE TO DO WITH THE IGNITION TIMMING AND ADVACE CURVE,

WOULD LIKE TO NO OTHER OPPINIONS

Drop the caps lock or I will delete these threads.

What do you mean by MK1 and MK2?

I have the service manual and parts book here.

The jetting was changed as the models progressed, along with the carbs getting bellmouths. and the ignition box for the NC24 was different.

The later NC21 (semi naked) VFR400-ZH uses the same setup as the NC24.

Why do you think they make less power?

http://www.honda.co.jp/news/1986/2860718.html

Here is the Honda press release for the NC21 from 1986 clearly stating 59PS output, this is the same as the NC24 and the NC30.

Torque is slightly down though compared to the NC24 / the later NC24

http://www.honda.co.jp/news/1987/2870320v.html

You can see the press release here showing the SAME power but an increase to 4.0kg-m/rpm of torque

[thunderace]

21 and 24 engines are the same except for the carb jetting and a couple of minor revisions of the internals. They are all the same engine model code.

[tragos]

86 models has a cam pos sensor at front head. has different cdi box that combined with this sensor.
has lower comp ratio 11/1
13000redline
taller 6 gearing
29mm carbs and some more differences..
it needs some mods to use an 87 engine on an 86 bike.

[Neosophist]

21 and 24 engines are the same except for the carb jetting and a couple of minor revisions of the internals. They are all the same engine model code.

Theres a shit load more difference than that. While they are the same cases (NC13E) as the NC24 and NC30, pistons / rods / valves / cams were all changed for the NC24.

You can read about the detailed changes on the Honda website.

The NC24 is a lot closer to the NC30 than the NC21.

86 models has a cam pos sensor at front head. has different cdi box that combined with this sensor.
has lower comp ratio 11/1
13000redline
taller 6 gearing
29mm carbs and some more differences..
it needs some mods to use an 87 engine on an 86 bike.

The stock NC21 has the cam position sensor and the different ignition box and the lower compression ration. the Carbs are 30mm NOT 29mm as opposed to the 32mm carbs used on the NC24 / NC30.

If you read my first post, the laster NC21 (VFR400ZG (naked style)) used almost the same set-up as the NC24.

http://www.honda.co.jp/factbook/motor/V ... 9/002.html

Here is a link summarising the changes between NC21/NC24.

In a nutshell.

Using velocity stacks on the carbs.
Changing the valve timing and largening the valves by 0.5mm.

Going from 30->32mm carb.

Chang in port direction and compression ratio.

Peak power is the same on all models but more torque and a better feel. Mainly due to overhaul of the intake / exaust system by way of vavles / pistons / rods / carbs / exaust system.

But yes, swapping between the different engines can be a pain in the arse mainly due to the plugs not fitting.

Putting an early engine bike a later bike is easier as the igntiino box isnt expecting a cam position sensor so does not require as much work.