GS1000 misfiring dropping 2 cylinders

[chandlerh2]

Hello to all My 1979GS1000 has developed a serious misfire . I have a dyna S ignition on it along with Vance and Hines header with racing baffle and pod air filters with a dynojet kit in the carbs .Bike has been running fantastic turn key and go . Sunday i rode it to brothers house was there for a hour . Got on bike fired up idling on all 4 cylinders and revved it and it sounded fine as soon as i took off and as i increased the throttle it started dropping cylinders cut back on throttle at low rpm's it runs on all 4 but as soon as i roll on the throttle it starts popping and drops 2 cylinders got it home put in a new set of spark plugs no change .. I replaced all the charging system about 2 months ago put in new stator and rectifier unit from Ricks electric also bypassed the circuit going through light switch bike reads 13+ volts when riding on the volt gauge i installed . Just tried to ride it again today and problem is still there but it certainly seems electrical . Where would you begin to look the Dyna unit or maybe a coil?? If its the dyna unit this will be the 2nd one i have had fail in a matter of a few years . I will put the good old reliable points back in . Any info would be appreciated .




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[zed1015]

May be a dyna pick- up failing.
Classic sign is cutting out as the load increases, also look for the white contact paste seeping from behind the suspect pick-up as that is a sign of overheating.
Duff coil can give the same symptoms but is easier to confirm or rule out.
Just switch the LT and HT leads to see it the fault follows the coil or stays on the same cylinders.

[uk gs nut]

Classic Dyna fail. Fit and forget, till it drops onto 2 cylinders. I bet its cylinders 1&4.

[chandlerh2]

Thanks for the info i will start testing today and see what i find

[Redman]

Tell us about the spark plug caps.

[chandlerh2]

Tell us about the spark plug caps.

When i installed new electrical components i got rid of the resistor caps and just use resistor plugs now.