Timing light question

HI guys...I'm slowly learning the tuneup process for my 1980 kz550 A1 with 4 into one kirker. Got the valves adjusted, cleaned out the carbs and installed new o-rings and got them sync'd. Now I'm trying to figure out the timing light. When I check the timing on #1 and #4 cylinders it's spot on with the strobe flashing like I assume it should nice snd regulsr flashes but when I check cylinders 2/3 I seem to be getting irregular or intermittent strobe flashes. It seems to flash better on cylinder #3 as opposed to #2. Tried to find info on this and ran across a post by Loudvhx couple of years ago saying timing light can help diagnose a misfire. Not sure what to do next about this. Any ideas? Haven't changed points or condensers yet but plugs are gapped to spec and fairly new. Bike has only 10k original miles. Runs pretty good with very smooth acceleration.

Swap plugs with 1and4 cylinders first and recheck with timing light to see if missfire moves to other coil.
Repeat with plug wires if possible. Recheck.
Swap signal wires from ignition to coils and connect plug wires accordingly and recheck to see if missfire moves to other coil.

Make sure positive power lines to coils, and grounds are all good/clean/tight.

If missfire moves with plugs - plugs bad.
If moves with wires - wires bad.
If moves with coils - coil bad.
If doesnt move ever on diff plugs/wires/coil, check ignition signal lines, pickups, and rotor condition and position to pickups with ohm meter as per manual.

Time to become a mechanic... :laugh: start systematically eliminating possiblities until you discover the culprit and replace/correct it.

Should take less than 1 hr.

Good luck.

Thanks TeK9iNe for the info...will check it all out next weekend. Just curious though, if I do have some sort of misfire there shouldn't you be able to detect it as your riding the bike? I haven't detected any "missing" while riding.

rf56 wrote: Thanks TeK9iNe for the info...will check it all out next weekend. Just curious though, if I do have some sort of misfire there shouldn't you be able to detect it as your riding the bike? I haven't detected any "missing" while riding.

Sometimes when there is a weak connection/coil/wire/plug/etc... it will only missfire at idle when the coil voltage is lowest, or the pickup is not being activated quickly enough (too large gap/worn out), or the resistance in the bad wire is not overcome yet... etc.

Idle missfires are common with old components.
The best investment for reliability on these old bikes (in my opinion), is to replace the ignition system (pickups - (dyna s, oem, whatev...), coils, wires, and plugs and related wiring), all with brand new.

Best of luck.

There can be many reasons why a strobe will act erratically. (And I'm not aware of all of them.)

The first thing to figure out is if the strobe is flashing at the right time when it does flash.

Is there an advance dial on the timing light? If so make sure you tape it to zero so you don't accidentally move it. (The numbers on the dial won't correspond directly to the advance on the bike.)

If the flash is erratic, but is flashing at the right time, most of the time, then it is more likely an issue with picking up the signal. If your light requires a large clamp on the plug wire, then I find it is harder to get the clamp all the way closed on the 2/3 wires. You have to make sure the strobe's clamp is 100% closed all the way around the wire.

If it is flashing at the right time, and also at the same wrong place much of the time, then the points may have an issue. It could be a metal filing or some dirt in the points, or if the points are pitted, this is very common.

Also, does it still act erratic at higher RPMs (but fine on 1/4)? If so then this would be more likely an issue with the signal getting to the light.

It's a 14 dollar strobe from harbor freight/no advance dial. Seems to work perfectly on 1/4 at idle and to full advance. The clamp is appears to be all the way closed on 2/3 and appears to fire about half as much as it should but at right time. These points(right hand set) are just a little off. Thanks for the help guys, will check it out again the weekend.

loudhvx wrote: There can be many reasons why a strobe will act erratically. (And I'm not aware of all of them.)

The first thing to figure out is if the strobe is flashing at the right time when it does flash.

Is there an advance dial on the timing light? If so make sure you tape it to zero so you don't accidentally move it. (The numbers on the dial won't correspond directly to the advance on the bike.)

If the flash is erratic, but is flashing at the right time, most of the time, then it is more likely an issue with picking up the signal. If your light requires a large clamp on the plug wire, then I find it is harder to get the clamp all the way closed on the 2/3 wires. You have to make sure the strobe's clamp is 100% closed all the way around the wire.

If it is flashing at the right time, and also at the same wrong place much of the time, then the points may have an issue. It could be a metal filing or some dirt in the points, or if the points are pitted, this is very common.

Also, does it still act erratic at higher RPMs (but fine on 1/4)? If so then this would be more likely an issue with the signal getting to the light.