Looking for some help from the airhead gurus on this site.
Three times this in the last two months, my '83 R100RT has ran really rough. In all three cases, the temperature was around +5F. The first time, I was accelerating down the road and when I reached about 45 in 3rd, there was a sudden loss of power and a vibration. It almost felt like maybe it was running on one cylinder. I made it home at 40 mph as there wasn't really any traffic. An hour later, it ran fine. I was guessing possible water in the gas since it had sat outside for 9 hours. BTW, no problem starting at these temperatures. I added some Heet to the gas tank. The next day, I rode it to town and at about the same speed, a smaller loss of power and some vibration within a mile of starting. I turned the enrichener to full and it went away. After another 1/4 mile, I turned the enrichener off and all was just fine.
Yesterday, it happened again and turning on the enrichener again, allowed me to get home but it wouldn't idle and would alternate between low power and normal. Very unnerving when riding uphill on snow as the pusher would start spinning when the power came on. As would be expected, it was running very rich when I arrived home but would barely run when the enricheners were turned off. Before it happened, no problems and even stopped a few times to take pictures.
This morning, everything normal again. Hard to debug as the engine won't idle. Normal running, the plugs are a nice light brown. After one of these incidents, very black but not wet. Lots of fuel running through the engine as my last gas mileage check was only 21 versus the normal 28.
Any thoughts? I was wondering if a bad bean can, ignition module or coils would behave like this? The carbs were rebuilt last winter and I've put on about 4,500 miles since then. They were rebuilt since it was behaving like this last winter and I assumed carbs. After the rebuild, it didn't happen again until October when it started getting cold again.
Valves are adjusted, heat sink compound redone on the ignition module, carbs rebuilt, new fuel filters, tank clean. All of this checked or done this past 6 months and none right before any of this started happening. I did check the coils for cracks last year and couldn't find any but I wasn't really sure what I was looking for. The bike has been in regular if not daily use since last April.