Help me troubleshoot my ignition issue

[Guest]

Hi all, I'll try my best to give a brief background on the condition of my bike and the issue I'm currently having. If I've left out any helpful detail, please let me know. I know this is a lengthy post, but have tried to organize it better than stream of consciousness and use proper punctuation to make reading easier.

The bike is a 1980 GS450 L.

Maintenance completed that may relate to this issue:
-Full GSR style carb strip & dip with cycle O-rings
-Shindengen SH-232 RR (verified good charging and voltage does not exceed 14.2 at 5000 RPM)
-Coil relay mod
-New Yuasa battery last season

Symptoms:
The bike has been running great for the last 3 years. It has run well all season this year until last Thursday.

I rode from my house to work about 35 miles without a single issue.

After work I rode about 5 miles from the office to a friends house, then rode about 10 miles with that friend.

I then began the 35 mile ride home from that friend's house without issue until I was about 5 miles away from my house. The bike started to misfire, then dropped to one cylinder, and finally just died when I pulled the clutch in and would not restart, no spark.

Roadside troubleshooting performed that night:
1. First thought was the relay used for the coils had gone bad, so I used a jumper wire to bridge terminals 30 and 87 in the relay connector block, still no spark.

2. Second thought was blocked vent at gas tank cap, removed cap and heard no air rushing in, and still did not start with cap off.

3. Called for backup and had someone get my truck from the house and pick me up.

4. Just for kicks, I tried starting the bike again about 15 minutes later and it fired right up

At this point I was suspecting a heat related failure of an ignition component as it was about 90 F and I had been riding in city traffic for over an hour before the bike died.

Troubleshooting performed at home the next day:
1. Tested coils, 3.9 Ohms primary on each coil, ~17 K Ohms secondary. The secondary reading is low according to my manual which states it should be between 25- 35 K Ohms.

2. Tested spark plug caps, they are 3 year old NGK caps, and both tested in spec at 5 K Ohms

3. Tested battery voltage, 12.36 key off, ~12.2 with key on

4. Tested voltage at coil connecter orange/white 11.8 with key on

5. Tested voltage at igniter power orange/white 11.5 with key on

6. Tested signal generator per manual specs, 72 Ohms each side

7. Installed brand new NGK B8ES plugs gapped to 0.026 in

I decided at this point that everything tested in spec, so should road test again. The bike started right up no problem, run great for about 3 minutes, and then the same symptoms repeated and I coasted into a parking lot.

I called my girlfriend and had her bring my spare known good igniter from home, swapped that in and still no spark. Tested for +12v at coils and igniter again, both ~11.8 v.

So, at this point I'm a bit stumped. The likelihood of both coils always failing at the exact same time seems too slim to be plausible. I would have suspected a failing igniter, but my known good spare didn't cure the issue. I'm thinking that leaves just the signal generator, but I can't remember ever seeing anyone here on the forum who had one fail. There certainly seems to be some kind of heat related issue as the bike will start and run after cooling off for 20 minutes or so. Plugs are wet with fuel if pulled during the no start condition, so am not suspecting a fuel delivery issue.

I'm leaning toward going the Dynatek DS3-3C route to just replace the ignition with new, but am a bit wary hearing of Pete's issues with those modules failing too. Any thoughts or suggestions of better tests for signal generator?

[Kerry]

I'm thinking that leaves just the signal generator, but I can't remember ever seeing anyone here on the forum who had one fail.

I had my signal generator fail on me. However, the symptom in my case was the bike just dying suddenly, with absolutely no prior warning, when it got hot. Left to cool down, it would restart and run perfectly until hot again.

Unfortunately, I don't work on the bike myself so I can't give you any insights on diagnosis or repair. Just wanted to let you know that a signal generator failure is possible.

[eil]

Thanks for the well written explanation. It makes it easy to visualize exactly what's going on.

Your methods are pretty solid but two things stand out. One, most of your numbers are about a volt lower than I would expect for a healthy system and these ignitors can be sensitive to that. When you go to start it, does the starter turn the engine over quickly every single time, or is there some hesitation? If there's hesitation, your battery might be on its last legs, even though it's newer. Doubly so if it's ever been deeply discharged at some point in its short life.

The only other thing I didn't see you mention was a full cleaning and check of the wiring harness. Clean all the connectors (especially the ones going to the ignitor) with this stuff called DeOxIt or any other high quality electrical contact cleaner. Visually inspect as much of the wiring as you can, and break out the multimeter to check for zero (or very close to zero) resistance between the relevant wires.

Update re the signal generator: yes, that's certainly a possibility, one which often gets overlooked. The service manual does have a procedure for checking the pickups, it's a simple resistance check just like the ignition coils.

[posplayr]

Sounds like time for some direct measurements:
1.) does it spark. ?
2.) does the coil(-) modulate?
this needs to be done after it quits running.
3) I would also keep a volt meter on it just to monitor while you run it hot.put it on the O/w coil (+)
Measure the ac voltage on a pickup wire at cranking speeds when you know it runs. Check that after it fails to run.
you have been very thorough , and unfortunately this has gotten tricky so you have to start back at basics of where the ignition chain is failing? Process of limitation by detecting a failure to properly function.

[Devon]

Thank you all very much for the replies. I will certainly take these next steps.

To answer some of the questions asked in the replies.

1. Yes, it always cranks over quickly with the starter even when it quits running.

1a. This may be the cause of the lowish battery voltage as I've spent more time cranking than running at speed this weekend, so I'll put the battery on a slow charge tonight to be sure it is up to full voltage.

2. I do have deoxit for cleaning controls on old hifi equipment, so will certainly use it on the igniter and signal generator connectors.

3. I've unwrapped and traced the harness from the signal generator to the igniter, and from igniter to coils, as well as my wiring from relay to coil +12v, no chafed insulation, no burned connectors.

4. I did follow the signal generator static test in my manual and got ~72 Ohms on each side, I believe the range given was 60-80 Ohms so seems to test bang in the middle there.

Posplayr, excellent suggestion on running a volt meter while running to monitor for anything unexpected. Despite my SH-232 seeming to work well, this might be a good opportunity to upgrade to a series RR as well.

Thank you all for helping me plod through this, I will update questions that have been asked as soon as I get some time in the garage after work.

[Devon]

I've got an update for everyone here. I haven't had a chance to road test yet, but did get to escape for a few hours to the garage this weekend.

Despite checking the charging of the bike two weeks before I had the breakdown, I believe my old SH-532 was starting to break down and give me marginal performance.

I finally bit the bullet and ordered an SH775, I spent this weekend going through the harness and cleaning up all connections with deoxit and eliminating some clutter. With the SH775, I'm now charging in the low 13s to high 12s at idle, up to 13.5 by 2000 rpm, and a rock steady 14.2 at anything over 3000 rpm.

I believe eil was on to something noting that most of my measurements were about 1v low for that to be a healthy system. I may still need a new battery as I think the current one is right at the tipping point of failing a load test. It was reading 12.3 off the bike, and 13.2 right after I pulled it off of the charger. The next morning it was reading 12.5 unloaded and drops to 12.3 with the key on.

In any case, I'll try to get out for a road test next weekend to see if the ignition issue still exists, and if so at least I'll have ruled out the charging system as it is now tip top.

[posplayr]

Failing the load test could just means the battery needs charging. From the found of your numbers you are probably charging.if joy report the numbers after your battery is better we can diagnose other issues better.