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81 gs 750 no fire

  • Thread starter Thread starter shopguy
  • Start date Start date
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shopguy

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have gs 750 with no fire,put new igniter still no fire.when i was checking coils one coil has 12 volt onboth wires(orange&black/yellow)the other checked 12 volt orange,white checked to ground,sitting on bike left coil is hot right is cold butno spark at all.any help would be great
 
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alright but can you explain why one coil has 12 volts on both sides and the other is 12volt and ground,which one is bad or are they
 
The orange/white wire going to both coils is the 12 volt positive-this comes from kill switch. The other connection on coil runs to ignitor (one solid white to one coil, yellow/black to other coil (??)). At right time when triggered, the ignitor grounds out one coil, then the other- this is same thing that contact points do, open and close. If you have ignition on ,but bike not running the ignitor might not be grounding out one coil (the ignitor will be waiting for trigger signal), so you'll measure 12 volts on both of that coil tabs as there's no connection to ground.
Head to that link; unplug your coil connections and check primary resistance- should be 3 to 5 ohms if you got stock coils- which seldom go bad. Ignitors and/or connections are more likley culprits in non firing episodes
 
ill check ohms at coil,what is procedure fo testing signal or pulse generator
 
shopguy said:
ill check ohms at coil,what is procedure fo testing signal or pulse generator
Click to expand...
Head to that link- step 11 gets to the signal generator test. So you have yet to see this thing fire a plug? or was it ok, but something happenned?
 
bike was no fire when the guy gave it to me,ive already been thru carb,tested igniter last night it was good tried to test puls/signal generator with ohm meter but kept getting different readings ,using digital meter started at 746 stopped reading at 221,the only other thing is how the fuel lines hook to petcock looks like it uses vacuum line from carb to a diaphram on petcock not familiar with this setup.
 
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ok so i rechecked signal/pulse generator with other tester it said 324 ohms this is within range of 250-360 still no spark at plugs,coils tested at 4.3-5 ohms,what else could cause no spark,noticed it had oil sending unit is this just for warning or iit like generator that can shut it down under low pressure.
 
No the oil pressure sender won't effect ignition system.
Your signal generator seems good- doublecheck all connections from signal coils to ignitor and from there to ignition coils.

A few posts up, you said ".....tested igniter last night it was good "- how did you reach this conclusion?

Remember that when you test spark plugs for spark, both plugs on that coil have to be grounded to head - the current shoots down one plug lead and back up the other.
 
Also try Mr. Matchless's simple test; remove signal generator cover; remove #4 spark plug, reinstall plug wire and hold spark plug against head as to ground it. With ignition "on" (and kill switch on "run") , flick a small screwdriver tip across the face of the signal coil for #1 and #4 - this duplicates what that little metal tab on rotor does as it spins by signal coil telling the ignitor to fire 1 and 4 plugs. See any spark on #4?
 
found post that told testing procedure it went like this.uhhook blue &green lead from pulse /signal generator at igniter,on leads that go to igniter take 1.5 battery hook ground lead to blue side,with ignition on and kill switch on, plugs removed from motor grounded to engine briefly touch 12volt to green wire you get spark at plugs 1&4,when you take 12 volt off green wire 2&3 fire
 
Well, I'm impressed that you did the test- ignitor seems fine (when triggered by battery); now you need to determine why it doesn't get the urge when the signal coils do their thing. I believe the ignitor sends a small current to the signal coils which gets "disturbed" when metal tab on rotor flies by coil face -ignitor senses this and fires.
 
im going to try the other test you suggested that way the system is all wired back together as it shoud be,see if we get spark then
 
ok i tried mr. M signal test it did not work,an electrician friend of mine used his ohm meter on pulse generator his read 324 ohms,tested coil thru ht wires,1/4leads,2/3 leads with ignition off one coil triggered reading on ohm meter the other did nothing
 
Unscrew spark plug caps from a coil; stick meter probes into wires and measure ohms; stock coils are about 12000 ohms wire to wire. Check both ignition coils. What do you have?
Nothing when you manually tried to trigger ignitor with screwdriver tip? doublecheck to make sure ignitor is being fed 12 volt positive thru its connector- this comes from those orang/white wires that feed both ignition coils 12 volt positive.
 
will check with caps off but istill dont know why im getting 12 volt on both wires(orange/white from igniter and black/yellow from igniter to the same coil 2 and 3,other coil is 12 volt orange/white goes to on other wire white 1and4tried rotating pulse generator to see if it woul read change oncoils but it did not
 
the sparkplug caps have certain amount of resistance is this correct i ohms tested them 3 of them same reading other copletely different
 
Yes, the caps themselves might have an ohm measure of 5000 to 10000 each depending on maker. Corrosion can make it hard to get a decent reading. The coils are easy to measure once you unscrew caps and measure wire to wire.
 
alright done mr, m 1.5 test on igniter which is supposed to simulate pulse from pickup,had spark at plugs with this test.tried mr.m test on pikup by swipping thin screwdriver between contacts got nothing at all,so did first test prove that both igniter and coils are good and pickup is bad,did ohms on pickup got 324 tested my old igniter with 1.5 battery test and got no fire so it was bad,still stuck on coil that has power on both leads when you unhook at connector it is 12 volt orange wire plug it back in 12 volt both wires
 
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