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ignition problem

  • Thread starter Thread starter goggleboy
  • Start date Start date
G

goggleboy

Guest
I have a 1978 GS750 that feels like it doesn't have adequate power.
I've put the valves in spec, replaced the stock ignition with the Dyna-s
in conjunction with 3ohm coils and new 8mm suppressive wires, I don't think
I have resistor caps (from what I can see).
Already followed the carb cleaning guide with new orings, and I even
lapped the valves.
Things to notice: The outside plugs are always darker and more sooty
than cylinder 2 & 3 plugs. I average 20mpg , that is really bad. I just don't
know what else to do! Could this be an electrical problem with wires before the coils?
 
What does the spark look like on all four plugs? have you checked your voltage at the coils to make sure it's at least 11 volts? That is pretty crappy mileage, would make sense with the rich findings on 1&4. That could be caused by poor voltage to the coil or maybe settings on your fuel/air mixtures. What are your screws set at on the carbs? Hey I noticed in your previous threads you've posted about this exact problem before, and several times about similar problems (as far back as last summer). I'm surprised you're still having spark/dark plug problems. Have you been riding the bike this whole time, did you take all the good advice you already got?
 
Last edited:
its just shy of 11, I have the screws set 1 turn out air, and 1 1/2 on the bottom fuel.
Spark is VERY good and purple on all plugs when I check it statically, but for some reason the 1 and 4 plugs are black, very sooty when it runs. on 2 & 3 they are grey/milk chocolate.
Checked the wiring from the Dyna system, which, the dyna system puts resistance on the circuit going to the coils right?
 
Your mixture screws should be set 3/4 - 7/8 on the bottom fuel screw and roughly double that on the upper air screw. You could also have a high float level and/or incorrect jets too. Check all the basics on the carbs, I doubt the problem is related to the spark.
 
Nessism said:
Your mixture screws should be set 3/4 - 7/8 on the bottom fuel screw and roughly double that on the upper air screw. You could also have a high float level and/or incorrect jets too. Check all the basics on the carbs, I doubt the problem is related to the spark.
Click to expand...

What Ed said.
 
Ill try checking the float heights again... its funny because I keep thinking this is Ignition. Hooking up a timing light to each of the spark plug wires tells me a different story. 1 and 4 signals are not as consistent as 2 and 3. (when the strobe is flashing) this might be a dumb question, but the tip of the plug is going to spark/send a signal through the strobe regarless of the mixture in the chamber?
 
Could be a combination of carb and ignition.

I found after upgrading to dyna-s & dyna coils my bike ran like crap. This was not the fault of the dyna products, but the fact that they draw more power than the stock ignition and show up weaknesses elsewhere in the ignition and charging system. I too thought I had good spark but when I measured the voltage between the battery and the coils there was almost a 3 volt drop. As a result I did the coil relay mod and now only have a 0.1 volt drop and the bike runs like a champ. Initially I tried cleaning the switches and connectors but this made little difference in may case.

The extra power usage also puts more strain on the charging system, so you should search the forum and find out how to troubleshoot this and if not exactly within limits keep chasing it to find out why. I've been riding for a couple of years thinking anything over 13 volts was good enough but it's not; as a number of more experienced members pointed out.

Anyway this may or may not be your problem but it was my recent experience.

And I agree that your air screw & fuel screw settings are kind of back the front.
 
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