Spark Plug / Timing Light Question

I've been having some cold starting issues lately and so I cleaned out the enrichener circuit to make sure it wasn't clogged. However, I am still having the same problem, bike starts on first kick but has trouble staying going until warmed up. I have to give it gas while on the choke.

So, I decided to check the headers to see if they were all equally warm. Turns out the #1 and #2 pipes were cold. So, I hooked up my timing light to see if they were getting power, and the light on #1 was firing intermittantly, and #2 wasn't blinking at all. #3 and #4 were perfect.

My question is, when the timing light is hooked up, what triggers the flash? Meaning, does the spark plug have to fire for it to flash? Or does the flash mean that the plug got power. I'm just trying to track down whether it is either a fouled plug or electrical issues that are preventing these two cylinders from seeing power. Or even if using a timing light is proving anything here at all.

It just seems weird that these two are bad, seeing how they are on different coils.

I just picked up new plugs tonight, but won't be able to test until tomorrow morning.

Recently, I have cleaned and gapped the points, set the timing, did the WG Mod and sync'd the carbs.

Thanks.

My understanding is the source of the timing light firing is the same one to spark the plugs. The coils may be breaking down and it's not unheard of that 1/2 of a coil is failing,

Put in new coils and try again and this time use a spray bottle of water to see if this makes a difference.

I agree with Mfolks. It's possible you are losing spark through bad wires or bad coils. Are the coils new? How do the wires look?

"when the timing light is hooked up, what triggers the flash?"

When the spark jumps the gap of the plug, lots of little tiny electrons are going from here to there through the spark plug wire. This is current flow. Current flow through a conductor causes a magnetic field to expand around the wire (magnetic lines of flux). The magnetic lines of flux as they expand cut through the pickup of the timing light and trigger the internal electronics of the timing light to flash.

You might try testing for voltage supplied to the coil with a meter. Also check the connection from the coil to the points and the points to ground? And finally test the coil with an ohm meter to see if it is within spec.

HerrDeacon wrote:

Turns out the #1 and #2 pipes were cold. So, I hooked up my timing light to see if they were getting power, and the light on #1 was firing intermittantly, and #2 wasn't blinking at all. #3 and #4 were perfect.

My question is, when the timing light is hooked up, what triggers the flash? Meaning, does the spark plug have to fire for it to flash?

Is it the kind with a "clip on" thing that goes on the plug wire? That's an inductive pickup that sends a signal to the light to flash. Usually it will flash on a weak spark, but it will not flash if there is no spark.

HerrDeacon wrote:

Turns out the #1 and #2 pipes were cold. So, I hooked up my timing light to see if they were getting power, and the light on #1 was firing intermittantly, and #2 wasn't blinking at all. #3 and #4 were perfect.

I thought on the fours that #1 and #4 were on one coil, so they have to fire as a set. #2 and #3 should fire as a set off the other coil.

have you tried putting in new plugs?

You most likely have a carburetor issue. An inductive timing light will fire even if the plug doesn't fire because the plug is fouled. The inductive timing light picks up the voltage going through the plug wire to cause it to fire. If the light doesn't work, that means there is no voltage on the plug wire. In this case, I would start swapping plug wires to try and isolate the problem; that is 1 and 4 and 2 and 3.

You most likely have a carburetor issue. An inductive timing light will fire even if the plug doesn't fire because the plug is fouled. The inductive timing light picks up the voltage going through the plug wire to cause it to fire. If the light doesn't work, that means there is no voltage on the plug wire. In this case, I would start swapping plug wires to try and isolate the problem; that is 1 and 4 and 2 and 3.

wiredgeorge wrote:

You most likely have a carburetor issue. An inductive timing light will fire even if the plug doesn't fire because the plug is fouled. The inductive timing light picks up the voltage going through the plug wire to cause it to fire.

Hmmm..... the pickup on mine is a current transformer whose core opens and then snaps around the plug wire so I would think it can only work if a current flows down the wire.

As I understand it, since two plugs are in series on each coil, if one of the two is fouled too bad to spark, it also keeps the other one from sparking?

Negative... if plug #1 is firing normally, plug #4 can be totally totally fouled and not firing. If you are sitting there trying to time your 3 cylinder bike with the inductive pickup around the #4 plug with it will light the lamp at the appropriate time just fine.

Thanks for the replies and suggestions guys.

I put new plugs in it this morning and tried it out. Still not showing anything on #2 using the timing light. I took it for a spin and then pulled the plug and it looked great, nice and tan. I was expecting either black or wet, but it looked fine.

I also checked the voltage to the coils, getting around 11.8. Checked the coils with an ohm meter and both are witin spec.

One thing I found weird was when the bike was running I pulled the cap off the #2 plug and the bike started to stumble. Since the timing light was showing nothing I was expecting the bike to continue to idle as normal. Thinking that this timing light check is not really proving anything.

George, if you think it may be the carbs, any idea on what I should check or clean. I recently had them off to clean the enrichener circuit and it seemed fine. Pilot and main jets are fine as well. I'm a bit of a noob with carbs so I'm just wondering what else to look for. I'm going to see if I can get a chance to check the sync again tomorrow.

Thing is that it runs and idles perfectly when warm, When cold it starts on the first kick, but is hard to keep going.

I did recently change my petcock out, switching the stock vacuum activated one for a gravity fed one, is there any chance that this would make a difference?

Thanks again.

Another update.

Today I cold started it again and the #2 was still cold. Never really started to warm until I took the bike off the choke. The others were hot by then. So I took the carbs off again and cleaned the enrichening circuit again thinking that the #2 part of the circuit may be clogged preventing it from working correctly. Put it all back together but still the same issue!

I also sprayed some water around in the dark to see if I could see any sparks or arcing but nothing.

Like I said before I tested the coils for ohms and they are fine. I then hooked up an inline spark plug tester to check again to see if it was getting current and it is.

I'm at a loss. Any ideas would be greatly appreciated.