Hi I am new to the forum and I have recently aquired an NC21 in need of a little tlc and after looking at my engine and frame numbers wondered if some kind sole could help me solve a mystery.

I have used the chart on this page viewtopic.php?f=22&t=46482 to check out the engine and frame numbers, the frame number (NC21-1000278) matches up to a 1986 NC21 as expected, however the engine number is NC13e-1080326 which if i am reading the table right appears to coincide with a 1988 NC24, so it would seem that it has had an engine change at some point, If i am reading it right.

This in itself isnt a problem, but i was told that when the bike was running in the past it would cut out when hot and so the assumption was the CDI unit needs replacing, however i was wondering if someone had changed the engine to an NC24 but still used an NC21 CDI, would this cause an issue? the CDI in the bike has the part number 131800-0031, does anyone know if this would be right for the engine?

Also from descriptions i have seen the carbs seem to be NC21 style without the velocity stacks/trumpets on the air box side of the carb plate.

I would appreciate any help in identifying if i have a complete NC21 or a NC21/NC24 hybrid so i know which parts i need to get.

where is the ecu?


the nc24 uses an oki unit hidden under the rear seat

the nc21 uses a mitsubishi i think unit by the battery



the nc24 engine wont run with an nc21 ignition unit as the nc21 engine has a camshaft sensor.

you can see the camshaft sensor inbetween the V on an NC21 engine

also the neutral switch is different



this is an nc24 neutral switch

Thanks for the reply Neosophist.

First off my apologies, I posted the wrong link, the Identification chart i used was off this forum here: http://www.400greybike.com/files/models.htm


The ECU is behind the battery on the Left hand side of the bike and is a DENSO unit the same as in your image:

http://i.ebayimg.com/t/VFR400-NC21-CDI- ... ~60_35.JPG

With the large 'H' on the part number label.




As for the crank sensor and the neutral switch, I will have to take a look over the weekend when I get back to the bike, I don't recall seeing a neutral switch where you have indicated, but then I haven't looked for it so could have missed it.


I assume that as the bike did start and run until warm the ECU is correct for the engine, although I haven't seen it run myself I do trust the person I got it from (girlfriends cousin).

99% NC21 engine.

Upon a closer inspection around the engine this morning, I could not see any camshaft sensors in the vee ( i assume they would be obvious and the wires would be a give away).
and then when looking round the bottom end I saw this:


Which seems from your information it is an NC24 unit?
Which begs the question, does this mean I have the wrong ECU? and also, if someone has changed the engine I would assume the harness would have to change due to differences such as the cam sensor on the NC21?

Definitely causing some head scratching.

weird.

That looks like an NC24 engine, its leaking a lot of oil from somewhere by the looks of that.

I think its a bit of a bitsa, perhaps a crashed bike / blown up engine that was never finished off.

Is the neutral plug connected up? Follow the wire from it to see where it goes.. the cam shaft sensor is only a single wire that feeds the wiring loom.

The nc21 has a different neutral plug so the loom might be different, I dont think you can connect the NC21 ECU to and NC24 loom but ive never tried it.

what is the exhaust, high level / low level?

put up some good picture of the bike and ill let you know what i can see...

OK so I have dragged the bike out of the garage and had another look and realised I have made a bit of a schoolboy error the engine number is in fact NC13e-1030326 not 1080..... which does make it an '86 NC21 engine on the chart which matches the bike, when chasing the wire back from the neutral switch, which is connected into the loom, i followed it further and found what looks like the cam sensor buried in the valley on the front bank (about halfway along the head), although this ads mystery to the neutral switch position, where would you expect it to be on the NC21?
T
he staining on the bottom of the frame could be oil, but the fuel tank also had a couple of pinholes so this could have caused the staining on the bottom of the frame also.

I have uploaded a couple of piccies of the bike and engine.

Well i would say nc 24.if it got the cam sensor.

richyrd5 wrote:Well i would say nc 24.if it got the cam sensor.

NC24s do not have a cam sensor.

Thats an NC21 bike and Engine.

Not sure about the neutral switch, looks like it was probably a red-herring as ill have to check it over when im not at work and have parts books to hand.

It has NC21 forks, NC21 exhaust and silener, NC21 brake resevoir, NC21 hydraulic clutch, NC21 seat unit, NC21 ignition box.

My first indication was right that its an NC21 engine.

As for the confusion about the neutral switch.. a few years ago I did mention to somebody on here you can swap engines over no problem but one time the issues with a different neutral switch came up.

I will check in my parts books but I suspect the neutral switch design was changed mid-way thoguh NC21 production, not just was the NC24, as this really is an NC21 engine but it has the later style neutral switch.

Ill reply at a later time with some more information but its an NC21 unit you have there :)

Neo, your knowledge is impressive.