GSX1100G very weak spark

[rphillips]

How many volts does it take to fire a spark plug? I've checked the hot wire to both coils & am getting only 10.7 V, thinking that's why tiny spark. Wiring dia. shows current flows from ign. switch thru kill switch then thru side stand switch then to coils. I'm thinking go backwards, next ck side stand current, inlet & outlet, then kill switch, inlet & outlet, then ign. switch inlet & outlet. All fuses look good, could a fuse cause low voltage? Appreciate all ideas.

[Nessism]

10.7V isn't too bad. How are you judging spark? On a bright day it's hard to see a plug spark so don't assume the worst. Check in a darkened garage to properly judge.

[Redman]

10 volts at coils is quite marginal, and is probaably power while cranking the starter motor, so , yes, this is probably the biggest reason for weak spark.your interpretation of the schematic is not entirely correct.main fuse, to ignition switch (r/r ties in along the way), back to ignition fuse(and two other fuses), to kill switch, to coils (and starter button, and igniter). My experience is loosing a portion of a volt at each step of the way, mostly in the wiring, not the ignition switch iteself. Others have found ore than a volt drop I. Just the ignition switch.if you want to prove to yourself that this low voltage at coils is what is caused g weak spark, as a test, run your own wire from battery pos (or main fuse) (or aux fuse) to the coils. If you have heard of the “coil relay mod”, it is pretty much using a relay to jump power to the coils.

[rphillips]

Thanks, a bit more info. I'm in a relatively not bright garage. First no spark with orig. JR9B plugs, Just for kicks, pushed in a D9EA from my GS1100 & could see a tiny spark, back to the JR9B, looked closer, no spark. Bought new JR9B's & still no spark. back to D9EA & still a tiny spark. I've checked & found the same on cyl. 1, 2, & 4. Both coils are equal readings, 3.1 oam from + to - 0n inlet end & 36.4 K oam checking from #1 thru # 4 plug wires. I didn't check the V on either while cranking. Diagram in my manual goes...Batt...25A fuse...ign. switch...10A fuse...side stand relay...Eng. stop switch...then "T" splits sends V to to the coils & to the ignitor power source circuit. Reading again, now thinking side stand relay may not be the side stand switch as I had thought. Dang I always have hated this electrical stuff.

[bonanzadave]

1 If you have heard of the “coil relay mod”, it is pretty much using a relay to jump power to the coils.

Did it. Totally noticeable difference in starting. Use to have to crank it a bit to get fire. After the mod... it pops right off.

[rphillips]

Been looking & reading & getting more confused. I'm pretty simple minded & wondering if while I have the tank, seat, side panels etc. off, can I just (temporarily to see if it gets good spark & starts) connect a jump wire from batt + to orange coil wire. If this fixes the spark thing, then more searching the relay mod is in order, if it doesn't fix the spark thing, look somewhere else. Does this make sense or a dumb idea?

[Redman]

Oh..... a 1991... I didnt notice that (even though you did say GSX). Yah that schematic is different, having much different interlocks. So disregard my description of the schematic.

Yes, can jumper power to the coils (or at least can on 1980s GS), as described in post #3.

[rphillips]

Thanks Red, I remembered reading the coil relay mod part, but the part about the jump wire from the batt. just flew right over me. Guess I should slow down & pay more attn. Thanks