Power loss

[motoman]

Hmmmmm............orange spark.......

Not good my friend. Especially when you noted thr OHM resistance previously. That goes hand in hand! REPLACE THE COILS with KNOWN 3ohm coils.

[BA80]

OK, I put a set of coils off of a CB700 on and it made no difference.

I've run completely out of Ideas.

[motoman]

OK, I put a set of coils off of a CB700 on and it made no difference.

I've run completely out of Ideas.

Gonna HAVE to check that voltage TO the coils IS 12+ vollts(key on).

[BA80]

Gonna HAVE to check that voltage TO the coils IS 12+ vollts(key on).

It IS Brant....

I ran a wire STRAIGHT from the positive side of the battery to the coils and just to be sure. No difference.

[DiverRay]

Don't play with the "old" coils!! IF you want to try, heat them with a hair dryer and check all the resistance readings when warm. It should NOT change more than 2%, and if it does, they are bad. Unless you are finding a low miles, fairly new coil it would be suspect in my book. It looks like you have tried everything except replacing the wire harness and all devices. That is a PAIN, but just use the hair dryer to heat and recheck measurements. Something is going open as it warms up....

[BA80]

I have;

1) changed carbs 3 times
2) coils 3 times
3) plugs 2 times
4) checked valve clearances (& swapped cams)
5) checked compression
6) checked right handlebar switch
7) disassembled ignition switch and cleaned it
8) run a power wire directly from the battery to the coils
9) replaced the TCI
10) replaced centrifugal and vacuum pot 2 times

The only things I can think of I haven't replaced in the ignition or fuel system are resistor caps (they checked OK), pickup coils (also checked OK), and fuel lines. I am totally at a loss.

[dbeardslee]

Have you checked your electrical grounds?

[BA80]

I made y'all a little video of the issue. I made it with my cell phone sticking out my shirt pocket so it's not so hot but you can get an idea.

The first part is taking off in 1st. You can hear how when I WOT it, it stunbles all over itself for a few seconds then pushes through it and runs like it should.

After I slow down and shift up I hit the throttle again and you can hear it fall flat then start gurgling. This is what it does on the highway AND IT'S FRUSTRATING!!!

https://youtu.be/BLbZXaFoWlU

[JerseyJon]

Waxing philosophical

Maybe it's quantum mechanics: A symptom without a cause.

[dbeardslee]

I still think coils, however I'll make an observation. You mentioned first noticing the problem at high elevation, and that's an indication of fuel/air mixture. The air is thinner up high which will result in a rich condition in carbureted motors. Shouldn't be an issue with the CV carbs, but who knows. I know you said you've changed the carbs three times, but that's the main thing altitude is going to affect. I know you said it's doing the same thing at lower altitudes now, but the fact that it showed up first at high altitude has me thinking.

I had a boggy condition around 3-4k on two standards with '79 carbs earlier this year, and the cause was the same on both of them - needle clip position. I couldn't believe the difference one clip position made. On one bike the clips were one notch too low, and on the other one the needles that were installed had no markings on them. When I compared them with marked Mikuni 5GZ6 needles the ones that were installed were slightly shorter - about one clip position's worth.

If it was mine and I was POSITIVE the coils were good, I had good power to the coils, the grounds were good, and I had no vacuum leaks, I'd try moving the clips up one notch on the needles and see what I got. I'd also make doggone sure the slides were properly assembled and moving freely and returning properly inside the bores.

If you don't want to dive right into the carbs, you might try doing the throttle chop method and get a read on your plugs and see what they look like.

[BA80]

I'm convinced it's in the ignition. As I said I tried 3 DIFFERENT sets of carbs with 3 different sized jets. and it made no difference at all.

I it just started rearing it's ugly head when the ignition system was put under harsh climbing conditions in the thinner air and has progressively gotten worse.

There is no way that the 3 different and differently set up carb sets could all cause the exact same condition.

As I said before, the only 2 ignition parts I haven't replaced are the resistor caps and the pick up coils. I'll grab a set of caps off one of the other bikes at home and swap them out and see what happens. No matter if the swapping stuff around fixes the issue when I hit on it it'll no doubt at least make it DIFFERENT.

That's what I'm looking for before I start throwing money at new parts.

[bikerphil]

Plug wire caps may be arcing/cracked/shot/etc. You said they checked out, is that under high engine load?

[BA80]

Plug wire caps may be arcing/cracked/shot/etc. You said they checked out, is that under high engine load?

Pretty tough to check at high engine load. I ohmed them out and they checked OK. Never noticed any arcing.

As I stated, these caps aren't that old but they could be it since they are one thing I haven't changed.

[bikerphil]

I've had resistor plugs fail under high load, perhaps the cap could do the same? It sounds like you are losing a cylinder or two under that high load situation.

[BA80]

I've had resistor plugs fail under high load, perhaps the cap could do the same? It sounds like you are losing a cylinder or two under that high load situation.

Yep, and it gets worse as everything heats up.