nc21/24 frankenbike help

[oldfield429]

i have acquired an nc21 off my brother, with a 24 engine due to 21 engine being dead. got it finally back in one piece(ish) yesterday and no joy bringing her to life. id heard it was a straight swap engine for engine but reading though this forum im realising its a little more complicated than that. can anyone help iv only played with singles up to now a v4 could well be beyond me

its basically jus a straight engine block swap, carbs, loom cdi, coils everything is nc21 side from the block.

iv got two unused connections, one is a double that im starting to think is from a cam sensor?

edit -> the other is a female bullet single wire comes up from near the oil filler under a bubber cap, next to where a collection of wires come out, neutral sensor? or oil sensor?
iv read about another sensor hiding under the back of the block but theres no wires from it, and none to go to it, like a male bullet any one any ideas here?<- edit these actually go together, iv got the wires crossed here when i was following them :S

how essential are these sensors to convincing the cdi unit its ok to start? and iv read theres some splicing i need to do, but i cant figure out wat exactly needs splicing

thanks dave

[thunderace]

I take it you are still using the NC21 loom, coils and CDI?


If that's the case, I'd at least swap the coils and CDI for NC24 ones if you can, it should make life so much easier

[oldfield429]

iv found out the coils are nc24, nt sure if they are any differnt though, but everything else is 21

[thunderace]

You might have a little more success with an NC24 ECU/CDI

[oldfield429]

the more i read the more worried i get....

[oldfield429]

researching cam sensors i think iv discovered the problem :S the cdi is waiting for it to give it some info on cam position but the 24 lump doesnt have it on....

[Chrissy_J]

If you have an NC24 engine you'll need an NC24 CDI. That much I know for certain.
The NC21 has some sort of cam sensor on the engine that connects via a black 2-connector plug to the 21's TCI, which a '24 doesn't have.

[Neosophist]

Right.

NC24 engine.. you will need NC24 ECU/TCI box and the loom to go with it.

The NC21 has a different ignition box and different wiring loom.

Coils can remain.

The pickups / neutral plug is different on the NC21 engine.. and the ECU is in a different place (behind the battery.. on the 24 its under the pillion seat.

I suppose you could keep the 21 loom and 21 ignition box if you replaced the pickups / neutral sensor etc on the 24 engine with the ones from the NC21 (just find out whats got different plus on and replace as necessary)

but bear in mind it'd be easier just to transplanet the lot

The NC21 has different cams / pistons / rods to the NC24.

Both fire 180 so shuold be too mcuh work involed. post up soem pics / questions if your stuck and i'll try my best