i have bought a project vfr 400 rc21, the previous owner said the rc21 blew the engine and he put a rc24 in it however it still seems like it has a rc21 engine as its got the cam sensor wire.

anyway its not sparking on all 4 plugs it only sparks on the left side then when you switch the wires over it will then spark on the right hand and not the left hand. ive changed the tdi box and no joy ive also used one known good spark plug so to eliminate problems
ive also changed the wiring loom and no joy

any suggestions?

does the NC21 have coils? could be the coil pack has gone (I have had NC30/NC35 which have coil packs IIRC)

sounds like the coils are dead?

the bike has 4 separate coils, swap them around and see if the dead spark moves

Tested coils and have a spare set. Since it working when I switch the wires over I know the plugs, leads and coils are all ok

Have you checked the timing pickups?

Ah I think I can deciper your explanation now.

Firstly the NC21/NC24 has 4 coils.

Which wires are you swapping around?

What is the "left side" and "right side"

Since it has 4 coils and 4 numbers it should be easy enough to say which cylinders are working.

But from the description you had a dead pair of wires?

Eg.

Coil 1: No spark
Coil 2: Spark

swap the feed wires over and it goes to

Coil 1: Spark
Coil 2: No spark.

Hence you proving both coils are ok.

Have you tested for voltage at the coil wires?

It could be something as simple as a broken wire in the loom.. you will have to follow them back to their source and check for voltage along the way.

There is a high res wiring diagram for nc21 somebody posted up a while ago, it should help.

I thought it was a broken wire but when I check voltage I am getting voltage at all ht leads as for pickups they have been change for a new set

steveduffy wrote:I thought it was a broken wire but when I check voltage I am getting voltage at all ht leads as for pickups they have been change for a new set

Ah then this is interesting.

You have 2 pickup coils in the side of the engine, have you disconnect the plug and checked they are both within specification?

each one triggers a set of coils I believe.

Yeh disconnect the old one and it was ok but not great so changed it for a used better spec one

If all the component parts are ok then must be a wiring issue between the pickups and the ignition control unit