Need clarification on the igniter test procedure

[suzukizone]

Trying to work through a misfire problem on my '81 GS850G. I am reading the article by Mr Matchless entitled "TESTING THE IGNITION SYSTEM". I got this from the "ODDS & ENDS" section of BikeCliff's great site.

1. In item 12, testing for 12v current going into the igniter, it describes to test for this voltage between the ORANGE/WHITE & BLACK/WHITE wires in the plug GOING INTO THE IGNITER.

I get NO voltage at the plug connected to the igniter, but did get a reading of 12.28v from the plug that comes through the wiring harness and I am assuming those two leads are the ones connected to the R & L coils. Does that make sense?

2. I have the original & ancient stock coils on the bike but had replaced the HT leads with the carbon fiber resistance leads from DynaTech. Those leads do not allow testing resistance across the Secondary windings. (Don't know the science of that). If I remove the leads and test directly on the "pins" that these leads fit to when installed in coils, the resistance is 11.9 on the 2&3 coil and 12.6 on the 1&4 coil. This is with the multimeter set to 200k ohms. I take that to be readings equivalent to 11,900 and 12,600 respectively. Since that doesn't align with the 30-35k spec I am hoping it is still correct without the extra resistance provided by standard hard wire leads and resistor caps.

Well my aging brain is trying to manage these tests as outside of my normal area of knowledge & experience.

Any advice greatly appreciated.

The bike has been down since fall with me sporadically trying to figure out source of misfire under load. Health and some decline in mental abilities have dragged it out along with frustration & procrastination.

Thanks to all in advance.

Geezerly yours

DH

[Steve]

1. Sounds normal. Current goes from the battery (and R/R output) through the fuse, to the coil, then through the ignitor to ground. You should not see any power at any of the ignitor terminals except the orange/white wire that powers the box. Seeing power coming from the coils is good.

If your geezerness extends back to cars with points, you might remember that power comes from the battery, through the coil, then to the points. One side of the points is always 'hot', the other side is connected to ground. The coil fires when the points open. When they close, the magnetic field inside the coil starts to build again. The "ignitor" on your bike is just a box of transistors that replaces the mechanical points. There is no magic that happens inside that box, nothing is actually ignited, it's just the place where power through the coils is interrupted.

2. The Suzuki manual calls for 31-33 kΩ, when measured from coil cap to coil cap. Each cap is supposed to be 5 kΩ, which means that it should be about 21-23 kΩ from wire tip to wire tip. Stock wires are solid wires, so there should be virtually no resistance. I would expect stock coils to be that same 21-23 kΩ. Your measurement of 11.9-12.6 kΩ is low, but probably not a problem. I just went out to the shop and measured a new Dyna coil, its secondary resistance is 13.2 kΩ, so I don't think yours would be a problem. It is better to note that they are virtually equal.

.

[tom203]

I've tested a bunch of these coils... Secondary ohms (without caps )are typically about 12k ohms wire to wire...The original stock plug cap seems to be about 10kohm, so over these caps you'd get in 32kohm range. But swap in 5kohm caps,then you get in 22 kohm range cap to cap.

[suzukizone]

1. Sounds normal. Current goes from the battery (and R/R output) through the fuse, to the coil, then through the ignitor to ground. You should not see any power at any of the ignitor terminals except the orange/white wire that powers the box. Seeing power coming from the coils is good.

If your geezerness extends back to cars with points, you might remember that power comes from the battery, through the coil, then to the points. One side of the points is always 'hot', the other side is connected to ground. The coil fires when the points open. When they close, the magnetic field inside the coil starts to build again. The "ignitor" on your bike is just a box of transistors that replaces the mechanical points. There is no magic that happens inside that box, nothing is actually ignited, it's just the place where power through the coils is interrupted.

2. The Suzuki manual calls for 31-33 kΩ, when measured from coil cap to coil cap. Each cap is supposed to be 5 kΩ, which means that it should be about 21-23 kΩ from wire tip to wire tip. Stock wires are solid wires, so there should be virtually no resistance. I would expect stock coils to be that same 21-23 kΩ. Your measurement of 11.9-12.6 kΩ is low, but probably not a problem. I just went out to the shop and measured a new Dyna coil, its secondary resistance is 13.2 kΩ, so I don't think yours would be a problem. It is better to note that they are virtually equal.

.

Thanks Steve & Tom 203. Really driving me crazy as I can get that +/- 12k reading directly on the coil output pins. After I went back last evening (after reading a Mar 2018 thread I had started about this same issue) I threaded 6mm bolts onto the plug caps & replaced the HT leads as apparently I was able to get reading last year this way.

I got something in the 16k range on one coil once but nothing on the other, Went back to the first one and then got nothing and nothing on both finally. Trimmed off a bit of the HT lead at the coil end so I could clearly see the fiber "wire" but could not seem to get a contact or reading.

Was thinking I could simply buy some metal wire leads but found I must have tossed the old original resister caps years back. I might just replace the DynaTech leads and spring for resistor plugs or maybe the problem is not ignition but in carbs. I had gone over them months ago and was pretty sure they were spot on & clean. Wondering if one of the floats is hanging in some way and I am just not sharp enough to figure if ignition or carb is source of problem???

I am going to try my other multimeter but doubt that the first one is at fault. Gotta test though. Well. I hate to ride in the summer so have to look at bright side. *@%^$*@%^$*@%^$*@%^$ed that I missed fall, winter & spring riding so far.

Thanks,

DH

[tom203]

Skip messing around with coil leads,,etc, scoop a used set off eBay - unmolested ignition coils are very reliable. This will let you rule out the coils as an issue.. Here's a set off a 750 which should work for you. Note wiring leads on primary side, but maybe the connector is different??

https://www.ebay.com/itm/Suzuki-GS750-Ignition-coils/192928956976?hash=item2ceb764230:g:nhIAAOSw-HJcr0r4

[suzukizone]

Skip messing around with coil leads,,etc, scoop a used set off eBay - unmolested ignition coils are very reliable. This will let you rule out the coils as an issue.. Here's a set off a 750 which should work for you. Note wiring leads on primary side, but maybe the connector is different??

https://www.ebay.com/itm/Suzuki-GS75...IAAOSw-HJcr0r4

Thanks again tom203, appreciate the advice & links. Will mull it all over. I really think the coils I have are OK. I think some of the problem might be getting a good tight fit with the leads. Going to replace them with copper wire like stock and search for the old caps. Just can't believe I tossed them. Meantime while I ponder, 10 new jobs popped up between errant trees and bees needing attention, I'm off on a tangent for a few days.

Thanks again, letcha know.

DH

[suzukizone]

I've tested a bunch of these coils... Secondary ohms (without caps )are typically about 12k ohms wire to wire...The original stock plug cap seems to be about 10kohm, so over these caps you'd get in 32kohm range. But swap in 5kohm caps,then you get in 22 kohm range cap to cap.

I found an old set of NGK plug caps in a dark & dusty corner, looks like they were once on this or another bike from past but seem to be the right angles and reach. They are showing about 5k rather than the 10k you said was stock.

Could I use these without doing any harm? Not sure what the effect of these differing resistance readings means at the spark plug end and in the ignition system as a whole.

Thanks for your continued support.

DH

[tom203]

Either 5k or 10k will work.....probably a slight advantage to the 5, but I have no proof!

[suzukizone]

Either 5k or 10k will work.....probably a slight advantage to the 5, but I have no proof!

Thanks Tom203, I snooped around on the web and a lot of info indicates that a lower residence would produce a stronger spark but it would last for a shorter duration. It might also result in some radio interference or static but I do not use any devices such as radio or 2-way communication devices. I have enough to do with using every bit of my attention to stay alive when riding so I have no music or other listening devices to distract me. I just sing silently to myself in a pleasing tenor voice,...or so it seems.Thanks again.