no spark! 85 gs750se

[skitter]

Hello everyone i finally came across your forum , still searching for information on my problem , i picked up a bike for $600 ,1985 gs750 se , sat for uhh since 2009 so its been sitting awhile , has good compression all electronic dash , blinkers etc seem to be working but my main concern atm is no spark? , ive checked the coils reading fine , generator is fine ive pretty much followed the entier wiring harness yet i am getting no spark whatsover , i also have 2 of the igniter boxes (a spare new one came with the bike) 12v to coils just fine .. im really stumped if anyone has an opinion i would love to hear it , ive had the killswitch apart how exactly do i tell if it doesnt work tho .. i turn it off and the bike doesnt turn over , turn it on and it works (in my mind thats working? :P) thanks!

[BassCliff]

Greetings and Salutations!!

Hi Mr. skitter,

What is the voltage reading (at the coils and/or at the battery) when you press the start button? 12v? 11v? 10v?

Try this: Testing The Ignition System

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[skitter]

thanks im going to try that , you mean turning the motor over? the voltage i would imagine .. i know i have 12v with the power on , but never did try it while starting , i would assume this would be a voltage drop? im running a charge directly threw the bike atm im guessing that would indicate either a bad ignitor or a draw in voltage ... thanks again for the reply

[BassCliff]

Hi,

Yes, there is a voltage drop. A little is normal. But if there is too much voltage loss there may not be enough to fire the spark plugs. Cleaning all of the electrical connections and grounds is pretty much mandatory on these thirty year old wiring harnesses. The "coil relay mod" is a popular workaround for voltage loss at the coils. There's lots of info about these procedures on my website.

Thank you for your indulgence,

BassCliff

[skitter]

14v to 10.8 hrmm doesnt seem that bad i should get some type of spark

[skitter]

i've disabled the killswitch , neutral sensor / clutch sensor and kick stand sensor still nothing , running with charger headlight off i can get the coils to 12.2 volts still no sparkola

[skitter]

if anyone can explain where the actual grounds are ... im not seeing many , i mean \\, the block has one on the back man was that a pain to get to and clean .. but other then that im not seeing anything else grounding to block?

[SVSooke]

That is the only stock ground on these bikes.Go to my 750 thread in my sig you will see I had mine to a bare frame.Added a couple more grounds while I was at it

[skitter]

That is the only stock ground on these bikes.Go to my 750 thread in my sig you will see I had mine to a bare frame.Added a couple more grounds while I was ay it

nice bike , im actually located in Campbell river lol , did you ever have any problems with your ignitor? i have two but maybe the odds are against me and thats my problem

[SVSooke]

nice bike , im actually located in Campbell river lol , did you ever have any problems with your ignitor? i have two but maybe the odds are against me and thats my problem

No I have not.Unless there was a R/R or stator failure that blew out both boxes you should be good.I have'nt got an extra box left either

[skitter]

so lets say i really dont know what im doing but i unplug the neutral wire sensor ( which by the way is just covered in oil ) ... does this need to be grounded now? the killswitch i had to power one side of the wire .. what im going to do i think is put everything back together and test this neutral wire because i noticed how cake it is with oil however i dont really understand the procedure to eliminate this (for now) do i need to ground it or attach the wires together? ...

[BassCliff]

Testing the ignition system

Testing The Ignition System
by Mr. Matchless

Properly localizing a problem with the ignition is sometimes a bit confusing and the following below should of assistance:

• Basic test, remove spark plugs. Fit them to the plug HT leads and ground them to the engine. Turn engine with starter and see if plugs spark. If any one spark plug does not spark swap it out. If the spark seems good on all 4 plugs, the ignition system is very likely in order. If spark is not present or very weak proceed with the following tests.
• Remove the tank, left side cover, seat and signal generating unit (pickup) cover at bottom right of engine.
• A good habit is to check the coils and igniter to see if they do not get very hot once the ignition is switched on, as this will most likely be the indication of a failed component of faulty connection or wire.
• If the spark is weak but present, inspect the HT leads and plug caps. Suspect coil wires and spark plug caps, or voltage at the coils and thus the battery condition. It could also be due to coils with partially shorted windings, but do not jump on this cause immediately, and they may get hot.
• Overheating coils with no spark may also be due to them getting a permanent full ground either from a faulty igniter or a grounded and pinched wire. Disconnect the coil plug connectors and proceed with tests.
• Measure the battery voltage directly across the battery terminals. If lower than approximately 12.6V first charge battery fully before proceeding.
• Next measure voltage over the coil connector plug, orange/white wire and the battery negative terminal. If lower than 12 Volt inspect the wiring for poor contacts and localise cause of voltage drop.
• Again measure directly across the battery, but pull off the spark plug leads to prevent engine from firing and swing with starter. While starter is turning the voltage should stay at least above 11 Volt. Also swing the starter with the headlights on to see that the voltage does not drop significantly at the coils while the starter plus headlights load the battery, which could prove that even if your battery is fully charged, it cannot give full or sufficient current and is on its way out or your starter may be drawing excess current (usually unlikely if starter is spinning at full speed) and pulling the battery down. If it drops much lower, charge battery fully or have it load tested and replaced if faulty.
• If all is well up to here you can assume your battery and the positive feed to your coils are in good order.
• With the coil plug connectors disconnected, use an ohm meter and measure the resistance of both windings on each of the coils. Exact resistance measurements are not too important, but continuity of the windings close to the approximate resistance values given indicates that the coils are in good condition. It must be noted that it is possible for the coils to only show up a fault when at higher operating temperatures, but this does not happen frequently.
  Ignition coil resistance:
  Between the two HT plug caps of the same coil, secondary HT winding, approximately 30 - 35 K ohm
  Between the orange/white and white on the first coil and orange/white and black/yellow on the second coil, primary winding, approximately 2-5 ohm. If this test is within limits you likely have two good coils.
• Locate the igniter and disconnect the plug with the blue and green wires coming from the signal generator (pickup) at the right bottom of the engine. Test the resistance across these wires coming from the signal generator pickup coils, it should be approximately 250 - 360 ohm. If this is in order you have proved the pickups and the wires to be good.
• The little back box or igniter is now tested as follows. With the ignition on, kill switch on, test for 12 Volt DC between the orange/white and the black/white wires in the plug going into the igniter. This proves that it is getting the correct voltage.
• The next step is to prove whether the igniter is powering your coils. Remove all 4 spark plugs and connect the HT lead caps to a spark plug #1, #2, #3 and #4 which is grounded and located to enable you to see the spark. Ensure all the connector plugs are back in, except the one with the green and blue wires from the signal generator.
• To simulate the small voltage generated by the pickup coil, prepare an ordinary 1.5V dry cell with two wires red for positive and black for negative. Connect the negative black wire from the dry cell to the blue wire on the connector plug going into the igniter. Switch on the ignition and kill switch to power the igniter and briefly touch the red wire from the dry cell positive to the green wire connector going into the igniter. You should see a spark on plugs #1 and #4 when you touch the wire and on #2 and #3 when you remove the wire. If this works your igniter is in a working condition.
• One other check that is often overlooked. Run the bike at night with all lights off in a dark area and check that no sparks are jumping from the HT leads to the frame or tank. If so they may need replacing.
• At this stage if all tests have passed you MUST get a spark at all the plugs when everything is reconnected and the engine is turned with the starter.
• If a spark that was previously missing has mysteriously appeared, have a very good look at your wiring and connectors, as something may be making intermittent contact and corrected itself temporary when you moved the wires.
• If there is a spark, but the engine will not fire, it could be due to ignition timing, valve timing or fuel problems. Ignition timing and valve timing problems are more likely on a bike that has not run yet after being disassembled and more unlikely to be the cause if the bike was not taken apart and was running before.
• A quick test with a few drops of fuel directly into the cylinders before replacing the spark plugs and then trying to start will prove it to either the fuel system or ignition system.
  1. If the engine then starts and runs for a few RPM's the ignition is correct and you need to look at the fuel and carburettor side.
  2. If the engine does not fire, but occasionally gives one load pop through the carburetors or even exhaust, it may be igniting when the valves are open, the valve timing may be a problem, cam chain or swapped wires from pickup - plugs firing at wrong time.
  3. Other reasons could be extremely low compression, too tight valve clearances, thus not closing fully (usually unlikely on all cylinders at the same time, but plausible), carburettor faulty or dirty, fuel line, filter or petcock faulty. Filter can cause an airlock if not positioned properly to allow free gravity feed.
  4. Then finally the ignition timing must be set properly. At less than 1500 RPM connect a timing light to #2 or # 3 spark plug and check that the timing marks line up for 2-3 on F, then move to #1 or #4 spark plug and check that marks line up for 1-4 on F. Check the advance by pushing revs up to 2350 RPM and the timing marks should both line up on the 45 mark behind the signal generator mounting plate through the sight hole at the top. The three mounting screws can be loosened and the mounting plate can be moved slightly in the elongated holes to meet this.

[skitter]

i actually followed those same directions however i didnt realise i could check 12v at the ignitor connection heh , wasnt getting spark out of the box jumping them , i'll have to check that

[BassCliff]

Hi,

i actually followed those same directions however i didnt realise i could check 12v at the ignitor connection heh , wasnt getting spark out of the box jumping them , i'll have to check that

OK, thanks. I just wanted to make sure you had seen the procedure.

There's also these:

Igniter/Signal Generator/Coil Test
Igniter Repair/Testing (2MB PDF)

Thank you for your indulgence,

BassCliff

[skitter]

so im stoked i found out the orange white / black yellow wire is not getting 12 volts .. this is good news im thinking now to find out why .. lol