Temporary Power Loss

I rode about 15 miles on freeway. After exiting, I drove through Rockville, MD to meet a friend for a ride today. Out on Wootton Pkwy, pulling up to a light, the motor felt weak, then a lower idle speed. It kept running. I stopped, emailed from my iPhone, then I re started. The motor felt like it had lost power on one or two cylinders. I started to head home on surface streets back to Arlington, VA. Lower power, long clutch engagement, staying in the right lane, lots of lights on Rockville Pike. I was able to keep up the slow pace without getting run over. As I had driven about five miles, I just made it to north Bethesda, the regular power came back on. That made getting home safer and more relaxed.
Any ideas on what I should look for on this temporary power loss?
The fuel filter was recently changed.
Thanks,
Bill

 

Did you or who ever change fuel filter, put a bolt into the rubber line to block it? Threads will tear off bits of rubber, check filter again. Other than that, it might be intermittent connection to ignition wiring.

When I was in college in the early 60's, there was a custom machine shop behind our apt. The little old Italian machinist made custom racing cams. He said there were the 3 C's needed for power. Compression, Carburation (FI today) and Coil (ignition/spark).


Since you problem cleared up on it's own, you can rule out compression, which leaves carburation and ignition.

 

Good quote. I'm still carb uretted. I replaced the filter and its fuel lines with out a plug. I'm thinking coil/plug cable/cap.

 

You always want to check what was last worked on, however, I recently went to a louder horn, which was a bitch on the 6th gen. While up under the nose, I noticed a bolt fell out and one of my ignition coils was loose! (Mine has an integrated coil/plug cap). Check all your wiring. You never know what you find!

 

One of the pulse generators could have temporarily quit; often bike runs fine until full operating temp is reached, then it quits, won't work right again until things cool off. Sometimes bad ignition coil can act the same.

 

I had an issue with mine that was similar. I had the bike a part for a coolant flush, valve adjust, new plugs and air filter. Ran it to sync the carbs and noticed a skip in the idle. Turned out the spark in the 3rd cylinder was arcing inside of the cap. Replaced it with a new NGK cap and voila! Oh course I also had a problem with my carb which led to the tear down. The diaphragm had somehow come out of the groove which created a terrible vacuum leak rendering that carb useless past idle. Anyway, food for thought!


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Finally got some time in the driveway today. Ref, Service Manual p. 16-6. Volt meter reading on the coil, measure resistance at the terminals. Spec is 2- 4 ohms. I got zero.
Measure resistance, one contact in the spark plug cap, the other contact at the upper terminal of the coil. Spec is 17 - 24k ohm. Looked like 30 to me.
I'm using an old, little Radio Shack multi meter. I might need a new one for critical measurements.
I'm wondering about the zero resistance measured across the coil terminals.
After tomorrow's crappy weather…. I'll try to check the pulse generator. Standard = 200 - 400 ohms (pg 16-7)
It's not much to go on yet, but I did get started.

 

I doubt a cheap little RS meter is going to measure such a low impedance (2-4 Ohms). In the world of resistance 2 ohms is pretty close to 0, a dead short, it is going to take a good meter.

 

My little RS multi meter is good for very basic stuff. Although I did get to measure at least two coils and caps before the snow hit. With my meter, I would say my coils/cable/caps are in the ball park. When the temp jumps up again, I'll check for fueling. There is no filter past the fuel pump. I'll drain my bowls and see if any poop comes out. Either sparks die or no gas is getting to the jugs.
Right now we have a few inches of snow, sunny and 18 degrees.

 

Keep a spare plug in your pocket and test for sparks on all 4 quickly after power loss, looking for a fat, blue spark or lack thereof.

 

That's a great trick.
Sometime when things aren't freezing, I'm going to look into fueling/carbs.

 

Unfortunately the two front plugs aren't that easy to get to


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Exactly right. The front plugs are hard to get too. In order for the trick to work, you only have to access the plug connector. Pull it off, turn it around and insert the spare plug. Check for spark.

 

That's what I mean. I thought just the caps are hard to get to


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Not at all if you remove the 2 bolts on the radiator bottom edge and swing it up.

 

On the petcock, the filters are embedded with an o ring. Do they separate?
The little tube on the lower right, had gas weeping out while the tank was upside down. Is that normal?
The petcock was doing some small leaking through the hose connector. I wanted to check it.
The petcock looks like it can't be rebuilt by replacing the diaphragm rubber and spring. Oh well. I'll take the petcock to the shop to see if the o ring is replaceable now.

 

I ordered the petcock o ring.
Next, I'll put it together and warm it up. Hopefully, I'll have one of those power loss episodes. Then, I'll check the plugs firing by the method Squirellman recommended.
We'll see. The weather is still chilly.

 

So far the bike has been running like a top!

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The petcock o ring is doing fine.
I checked the plugs today. All 4 have spark. Looks like a fuel problem.

 

Disassemble your carbs and use compressed air (carefully) to blow any carp out of the carbs and jets.

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