Intermittent rough running

[vincent]

Hi all,

I've had my black '77 GL1000 since 2011, and it's all stock and original except for Fiamm horns, Dyna coils, and Dyna ignition. When I bought the bike, the odometer was stuck at 34,000, so I really don't know how many miles are on it. It recently developed a problem that's driving me nuts. In the middle of a normal ride, it will backfire through the mufflers, lose power, accelerate verrrrry slowly, and I'll have to use about 3/4 throttle just to keep it at 45 mph. It makes a deep tone that sounds like an unfiltered intake roar, and uses a crazy amount of fuel. Sometimes it lasts for a few seconds, but sometimes I've had to limp all the way home like that. When it suddenly clears itself, it leaps forward (3/4 throttle!), runs smoothly, and accelerates cleanly and strongly. And then craps out again. I've replaced the plugs, plug caps, and plug wires. I've flushed the gas tank, replaced the fuel and air filters, rebuilt the carbs, petcock, and air cutoff valve with the Randakk's kit, and replaced the float valves and needles. During the carb rebuild, I blasted carb cleaner and compressed air through every jet and passageway. The fuel pump output matches Randakk's specs, and the coils and wires show proper numbers for volts and ohms. The timing is spot on, and the valves are set to spec. I flushed and refilled the cooling system. The bike is like Jekyll and Hyde - the two sides are so different that it's hard to believe it's the same bike. I love to ride it, but I'm afraid to take it out of the neighborhood now. I've tried everything I can think of, so if anyone has any ideas, I'd be happy to hear them.

Thanks for your time.
Vincent

[gltriker]

[Whiskerfish]

Most common culprit we have seen for something like this is a dyna module that is on it's way out. One side or the other fails when it gets hot and you loose 2 cylinders. About the only sure fire way to troubleshoot is to revert back to points or replace the dyna.

[vincent]

Hi guys- Thanks for the speedy response! The battery is just a couple of months old, and the electrical stuff - lights, horns, starter, etc. - all seem to work as normal.

I had always heard that electronic ignitions that fail do so all at once, and that the failure is total. Is that not the case? I've already spent a bunch of money on this with no results, but if the Dyna is a possibility here, I'll happily pull it out.

[gltriker]

Most common culprit we have seen for something like this is a dyna module that is on it's way out. One side or the other fails when it gets hot and you loose 2 cylinders. About the only sure fire way to troubleshoot is to revert back to points or replace the dyna.

agreed .

Hi guys- Thanks for the speedy response! The battery is just a couple of months old, and the electrical stuff - lights, horns, starter, etc. - all seem to work as normal.

I had always heard that electronic ignitions that fail do so all at once, and that the failure is total. Is that not the case? I've already spent a bunch of money on this with no results, but if the Dyna is a possibility here, I'll happily pull it out.

Want to learn a straightforward method to dynamically (running engine) test it ? You DO !

please read this:
viewtopic.php?t=76812

*

viewtopic.php?p=806163#p806163 download the very short demonstration video, too

20221025_152106_1_1 (8).mp4

[CYBORG]

plus one on the dyna stuff. I've had severalm fail in different ways, Your problem sounds like a module issue. Ck for good grounds, and that the cover isn't touching the modules from time to time. The cover gasket can get thin from tightening, and short out the module when the engine gets hot

[Sidecar Bob]

When one of my Dyna's modules failed it was about a month out of warranty. They stretched the warranty and replaced it for me and it is still working fine 11 years later.
Details here http://www.ngwclub.com/forum/viewtopic. ... 2c986dc197

[Fred Camper]

I lost the 1/2 pickup on the dyna module. Replacing the dyna resolved the issue. The 1/2 pickup is closer to the engine so perhaps that one runs hotter. Still solid state should not fail that quick but mine only lasted 7 years. Dyna did not replace it. My dime.

[vincent]

I just want to say thank you to everyone who responded to my post. The Dyna was the culprit. I installed it right after I bought the bike, which makes it about 13 years old. The idea that it was failing never even crossed my mind, but you guys nailed it. A new unit is in, and the bike is running great! Now I can start planning nice long rides again.

[redglbx]

, don’t know if you talked to the folks at Dyna but my experience has been that even if you’re way out of warranty they have almost always cut me some slack on the price of a new one.

I had a Dyna coil that had been in the bike for around 20yrs that ultimately was failing and causing run problems, they asked for both coils back to look at and diagnose the problem, they sold me a new set for a super reasonable price. I am a Dyna fan !

[vincent]

Well, I hope I never need to think about that, but it's good to know. It shows that they're in it for the long haul and willing to lose a few dollars for good will and reputation building.

1977 GL1000
1970 Triumph Bonneville
1973 CR 750 Replica
1976 Trackmaster Triumph

[Don R]

Years ago, Dyna had a parts failure problem, I think they got past that issue but the old ones keep popping up. I have a set also.

[Dirty Dave]

My Dyna S had a 1/2 failure. My diagnostic "skills" were off as I suspected a coil as I lost 2 cylinders
when bike warmed up. Wrong 2 for coil, right 2 for Dyna failure.

Live & learn.