So you think you've got a dead ignitor.  First let's try to prove if it's an ignitor or some other problem.  Ignitors with problems can often be intermittent, so you have to actually catch it failing to determine which one is at fault, but an intermittent problem where pairs of cylinders seem to suddenly drop out makes the ignitors your chief suspect. 

Have a look at the above diagram.  The diagram shows all of the connections that make up the ignition system on Honda V4 Motorcycles.  Most of the V4 engined Hondas use a separate ignitor for each cylinder pair.  If an ignitor is the source of the problem, two cylinders will be affected while the other two are not.  If your problem affects more than two cylinders, ignitors are probably not at fault unless you're unlucky enough to have two bad ones.  If you're convinced the problem is the ignition, but it affects more than two cylinders, check the battery, ignition switch, kill switch, main fuse, and wiring harness grounds for poor connections. 

(Repair hint #1: when checking the main fuse, actually take it out and hold it in your hand.  Main fuses have a nasty habit of cracking in ways that are not easily visible, but will fall apart into pieces when you actually take them out.) 

(Repair hint #2: there's a ground loop from the harness that usually connects to the coil mounting brackets that can cause odd problems if not connected.)

There's a couple of ways in which the ignitors be checked. 

First, note that one of the ignitors is used to run the tachometer.  If the tach goes wonky when the bike misbehaves, the ignitor running the 1-3 cylinders is a prime suspect, however keep in mind that things other than the ignitor such as loose connections or a bad coil could also cause problems with the tach.  On bikes equipped with a fuel pump, the 2-4 cylinder ignitor runs the fuel pump relay.  The symptoms here would be the bike suddenly acting like two cylinders dropped out and then a short time later completely dying as the rear cylinders run out of gas, however if the ignitor just goes nuts and supplies intermittent or poorly timed sparks, the fuel pump will continue to operate. 

Best thing to try in order to try to narrow down the problem is to swap the connectors to the ignitors and see if the symptoms move to the other pair of cylinders.  If the problem moves when swapping the ignitors, you've probably found the problem.

You can also check for dead cylinders by _carefully_ checking to see if the front and rear exhaust pipes are hot or cold.  I don't recommend trying to touch them, as the pipes can be extremely hot and will burn you before you can react to the heat.  Rather, just try and get near them and feel for radiated heat.  If you find cold pipes, try swapping where the ignitors plug in.  If swapping the ignitors causes the other bank of cylinders to go dead, you've probably found the problem. 

NOTE: In some of these bikes, one ignitor is physically larger than the other and may have a different colored connector, but the two units should still be interchangeable.  The larger of the two units has a rev limiter built in but is otherwise functionally equivalent.

If you swap ignitor positions and suddenly everything runs normally, you either corrected a poor connection at the ignitor connector or the disturbing of the wiring has temporarily gotten an intermittent connection within the ignitor to work again.  In either case, you probably want to check out the ignitor for solder problems detailed in the second bullet below or problems are likely to reappear in the future. 

OK, now you've found a dead ignitor, now what?  There's a few possibilities of what the problem is:
 

• Moisture has gotten into the ignitor and is interfering with proper operation.  Some of the bikes are prone to this happening because of poor placement of the ignitors, such as the V45 Magna.  Remove the ignitor from the bike, shake it, and see if any moisture comes out of the drain holes.  If so, opening the case and drying it out internally may restore normal operation.  There is a chance that the moisture has damaged the ignitor (most likely it'd be corrosion damage), but many return to normal operation after drying out.  If yours starts working, try and figure out how the moisture is getting in and figure out a way to prevent it in the future.  Even if moisture is the problem, you may want to check for the next problem as well, as it's common enough and could be the cause of more problems in the future.

• A solder joint or other mechanical problem has developed in the ignitor.  This is actually pretty common.  Time and thermal cycling weakens solder joints and they eventually crack and become open or intermittent.  The most common problems occur at where the wiring harness connects to the internal PC board.  To fix this, you'll have to get the PC board out of the case.  This is easier said than done.


First, pop the end cap off of the ignitor and slide the rubber grommet that the wires go through off the edge of it.  The cap is not glued to the case, but is snapped in place.  Next you need to slide the PC board out.  Sometimes this is relatively easy, sometimes it's a real bitch.  The PC boards of the units I have opened were not glued in place, but they had been covered with a sort of waxy material that was used to protect the board's components from the elements.  This waxy substance was on the edge of the board as well has over the components and effectively glued it in place.  The ones I've pulled apart so far have come loose without damage to the PC board.  I use a small jewelers screwdriver to carefully pry on one of the harness wires right at the surface of the PC board and the side of the case.  You need to be careful to pry very near the PC board surface and attempt to not put any side loading on the PC board itself or it might crack.

Once the board is out, inspect the solder joints.  The pictures to the right are examples of what poor solder joints look like.  If you see what appears to be a ring around where the leads are soldered to the boards, this is an indication of  cracks that have developed in the solder joint and it is well on its way to failing if it hasn't already.  One of the pictures shows the rings, the other shows a large fissure that has developed and the wire is free to pivot around the solder joint.  It was a miracle this ignitor was working at all.  Use a soldering iron in the ballpark of 20 watts and resolder the joints using rosin core solder.  Proper technique is to heat the joint, then add the solder after the joint has melted.  You should end up with a nice shiny cone at the joint and if this is done properly, it should only be necessary to heat the joint for a couple of seconds.  Extended exposure to the iron could lift the trace or otherwise damage the board.  Do not use acid core solder or the acid from the flux will eventually eat away the copper traces on the PC board.

Inspect the other parts of the board as well for any bad solder joints and resolder/repair as necessary.
 
 

• The other possibility is that an electrical component has failed.  While I consider this the least likely failure scenario, it does happen and at the moment there's not much you can do about it.  The active components used in the ignitor are either obsolete or custom and obsolete.  The driver transistor (the part on the aluminum heat sink) is the only major component (other than some of the discretes) that looks like it would be possible to find a replacement for.  I haven't personally tried these, but the transistor used appears to cross to an NTE2315 or BU806/BU807 type of transistor. 



Ignition Troubleshooting Checklist:

All cylinders have problems?

• Check battery
• Check ignition switch
• Check main fuse
• Check kill switch
• Check harness ground connections
• Check both ignitors
• Move on to other possibilites like fuel delivery
Two cylinders have problems that do not move when ignitors swapped
• Check power connections at coil
• Check plug wires
• Check plugs
• Check coils
• Check pulse generators
Two cylinders have problems that do move when ignitors swapped
• Check ignitor connections
• Troubleshoot ignitor