No spark

[Jaguarjoe]

I'm trying to resurrect a 1979 GS550L that hasn't ran since 1986. I have no spark on any spark plug.
Things I've checked-
I have 12 volts (10 V cranking) constant on top of each coil.
I have 12 volts (10 V cranking) across each set of points when they are open.
I have 0 volts across the points when they are closed.
Points open and close with the cam lobe.
I checked the static timing and its OK.
I took a coarse file and dragged a wire across it triggering each coil and got nice fat blue sparks from each coil. I'm at a loss as to what I'm missing here. How much more basic can two coils and two sets of points be?

 

[Billy Ricks]

Bad ground maybe?

 

[rustybronco]

I have 12 volts (10 V cranking) constant on top of each coil.

Good

I have 12 volts (10 V cranking) across each set of points when they are open.

Good

I have 0 volts across the points when they are closed.

Good

Points open and close with the cam lobe.

Good

I checked the static timing and its OK.?

Good

I took a coarse file and dragged a wire across it triggering each coil and got nice fat blue sparks from each coil. I'm at a loss as to what I'm missing here. How much more basic can two coils and two sets of points be?

Explain...

were the spark plugs in the plug wires and grounded to the engine at the time of the test? and did the spark jump across the air gap or from the outer shell of the plug to the engine?

 

[Suzuki mad]

If your getting power to the coils check for spark to come from the plugs. If no spark then it has to be leads, caps then plugs.

Is 10v enough at the coil end?

Suzuki mad.

 

[Jaguarjoe]

Explain...

were the spark plugs in the plug wires and grounded to the engine at the time of the test? and did the spark jump across the air gap or from the outer shell of the plug to the engine?

I stuck a philips screwdiver in the end of the plug wire and held it close to the valve cover. With the file test I get lots of good blue sparks- jumps 1/4" or more.
When I try cranking the bike over and holding a plug against the valve cover and I get no spark. Holding the screwdiver near the V/C also produces no spark when cranking.

This is too simple not to work!!!!!!!!

 

[rustybronco]

Remember fouled spark plugs usually will not jump the air gap.


disconnect the condensers and crank it over, then see if you have spark.

 

[Jaguarjoe]

Remember fouled spark plugs usually will not jump the air gap.


disconnect the condensers and crank it over, then see if you have spark.

I didn't try my file test with the plugs and I didn't try anything with the condensers disconnected. I'll give it another try tomorrow if it isn't raining.

BTW- How do you tell Nippon-Denso points and condensers from Kokusan points and condensers? Or are they interchangeable?

 

[rustybronco]

ok...
you have at or near battery voltage at the coils, correct?

when cranking you have approximately10v at the positive side of the coil correct? probably low, but should produce a spark, especially with a screwdriver inserted in the plug wire end and held near the engine block.

with a voltmeter connected to the junction of the primary coil wire (negative side of the coil) and the points. you have battery voltage (or near) with the points open and 0v with the points closed. correct? this means all is working well and the points have a good ground. if not there is resistance in the point contacts.

if the above is true you have a combination of low voltage at the coils when cranking and a VERY high resistance on the secondary side (wires, caps or both) of the coils.

or one of your measurements-observations are incorrect, please double check.
and check the resistance of the spark plug caps (open circuit, no resistance).

nothing else makes sense.

 

[Jaguarjoe]

if the above is true you have a combination of low voltage at the coils when cranking and a VERY high resistance on the secondary side (wires, caps or both) of the coils.

or one of your measurements are incorrect, please double check.
and check the resistance of the spark plug caps (open circuit, no resistance).

nothing else makes sense.

Do you know how many ohms should I get between plug #1 cap and plug #4 cap? Likewise for plugs 2 and 3?

I'm recharging the battery now while I'm stuck here at work

I double and tripple checked all my voltmeter readings before I posted anything here. I kinda doubt I have secondary issues because I get beautiful sparks with my file test. The only unkown is the condensers. I'll disconnect them tomorrow and retry with a fresh battery. Like you said, "nothing else makes sense."

I'm really itching to hear this bike run too!

 

[rustybronco]

Do you know how many ohms should I get between plug #1 cap and plug #4 cap? Likewise for plugs 2 and 3?

not positive 5k ohms for each cap and 20-30k for each wire

 

[Jaguarjoe]

not positive 5k ohms for each cap and 20-30k for each wire

I got 33K ohms across the 1-4 set of wires/coil and 35K ohms across the 2-3 wires/coil.

I found my spark! What I ended up doing was gounding an actual spark plug and watching its gap as I cranked it over. Yuo had to look close but it was sparking. Not nearly as fat as I'm accustomed to but it is there.

 

[rustybronco]

clean the connections... ALL of them and get that voltage up.

 

[Jaguarjoe]

clean the connections... ALL of them and get that voltage up.

An excellent plan!

 

[RMC]

An excellent plan!

What the end result?? What was the problem?

 

[Jaguarjoe]

What the end result?? What was the problem?

It was cockpit error. I wasn't looking hard enough to see the spark that was always there.

The bike started and ran fine after I cleaned the carbs a second time- this time paying close attention to the choke dip tubes and their little "compartment" in the bowls.

The bike still runs great- it reminds me a lot of the Triumph Bonneville I used to have back in the day. Its far nicer than the big Hog I had a few years ago. As old as this '79 is, its the nicest bike I've ever owned with much thanks to the people on the site that helped make it that way!