Flat spot/Bogging while cruising...

[anthony8488]

I'll have some time this weekend to do some multimeter checks on the igniters.

I have some extra fuel line so will cut a new piece and give that a try, I have a new inline filter on it now still clean but haven't checked the petcock filter yet so will give that a look as well.
When shooting wires of it's a hot wire it should read what the battery is reading right? And then no reading for grounds?

[TOOLS1]

Yes that is correct. Just be careful that you do not let the smoke out of the wires. It is impossible to put the smoke back into them, so they must be replaced if the smoke comes out of them.
TOOLS  

[anthony8488]

Gotcha, will take all precautions on preventing smoke release from wires!

[anthony8488]

So I replaced the fuel line, checked the petcock filter (it was clean), go to check the wires on the spark units and when I bumped the wires my lights were flickering.

I checked the terminals to find that my positive terminal warped and loosened the positive lead.

I had a battery tender plug wired to it but the positive side looked burnt and pulled right out of the eyelet connector. The 7.5 amp inline fuse, was still good.  Could the tender cable have caused the warped terminal?

Back to the spark units, battery tested at 11.70~, both units, tested 11.40~, is that close enough or is that  signs of bad spark units?

For the pulser coil coupler, it says:
Coil resistance : 530 +/- 50 ohms
between yellow leads
between blue leads

I had the multimeter set at 20k and got a reading of 3.7~ if i touched the yellow w/ blue tube and the blue wire together. I get no reading on any other combination. Are those the correct wires I'm suppose to use together and if so and I'm only getting 3.7 whats the next step?

[motogrady]

You've made a few changes, found an electric item, I'd take it for a spin.

After the battery got a good charge.

[anthony8488]

Okay so a good charge on the battery, bike fired right up, idled for the 15-20 mins I let it while I got ready to take it down the road, pull out of the drive way a couple stops signs and within a mile I lost the center two cylinders. Luckily this time it happened close enough to home I got it back into the garage and misted some water over the exhaust to notice which were hot.

Coils are checking good, so could this be one of the CDI units or still possibly the ignition? I did replace plug wires but if that were the issue it would show at start up and idle right?

Is there a way to the CDIs with a meter?

[motogrady]

Holy crap Anthnoy, I thought you had it.

I'd swap the coils around, try it, then the Cdi units, try it.
It happens to different cylinders, you got it.

Sounds like something is getting warm, or hot, then failing.
I've heard coils doing this.

Keep us in the loop guy.

[anthony8488]

Had a chance to take the bike out today, I had ordered new CDI units and installed those, bike didn't make it more then a mile down the road getting the same issue. I got it back to the garage and still the center two cylinders are what's shutting down. **bike can idle all day, I let it run in the garage for about 40min today before taking it out.

When I pulled plugs the centers look identical to the outter cylinders that are firing constantly, they all look dark and dry by the threads with the tip being a lighter brownish color.

I did swap the coil packs out with coil packs from a 95 cbr600 previously thinking  my original al coil packs were failing under heat. So my next step I'm going to try is swap the coil packs around and see if it follows a coil pack. I still have my originals so if it's a failing coil pack I'll have two more to try and swap in and retest. The 95 coils checked good on a meter, cold and off the bike which doesn't help if it's a heat issue.

I also rechecked the fuel line during the loss of power, was still nice and firm no kinks. And with the plug colors I think fueling is good.

Is there anything else I should check or recheck while I'm at it? The spark plugs being the same across all four should mean the mixture is good and tell me more so that spark is the issue still?

[motogrady]

Geez, head f&&ok for sure.

Seems to me, if it was electrical, the 2 center plugs would be wet when pulled, from lack of spark whilst still getting fuel.

But they're all the same, with good color to boot.  Hummmm.

Agreed, I'd move the electrics around, seeing if the problem follows.
Including spark plug wires, plugs, those 2 spark packs under the seat, the coils under the tank,
all one at a time until maybe you catch it.

I wonder. How could you see if the 2 center carbs were clogging and starving for fuel in this situation?
No lifters to fail with the valves, can't be that.
The carbs do depend on vacuum pulling on a good size diaphrag ..............geez.
I'm interested guy, please keep us in the loop.

[anthony8488]

So had some time to tinker on the bike...
So did some looking around and found that my carb banks weren't fully seated in, so fixed that.
Checked the gap for my electronic ignition magnets, they are both at 0.020mm, should be good (manual states 0.016-.027mm)
Pulled the coils off to make sure their grounds are clean and retested them on the meter both showing 3.8(cold)
Buttoned everything up and now it is constantly only firing 1 & 4. You can hear its not all firing and the center pipes stayed cool.
I swapped the plugs for the CDI units, problem did not follow.
I swapped the plug ends of the coils so 1&4 coil was now 2&3 and vice versa. When I try and start the bike, it'll crank a few times then make a shotgun sound. Switch the plug ends back around and the bike will turn over only firing 1&4.
I tried swapping the coil for 2&3 with two other coils (the originals i had on the bike that also meter good (cold)) and no luck, same symptoms.
Battery is fully charged, visually the spark plugs all look great, but I guess I could swap plugs from 1&4 with the 2&3 and see if that changes anything

So I feel like this is all telling me my problem is in that path for the 2&3 coil. What else is there to check to see if its the culprit? Feeling like the electronic ignition might have kicked the bucket. Thoughts?

[TOOLS1]

I would start looking at the carbs.
TOOLS

[anthony8488]

Just again as a whole? What should I be looking for?

Every time I've had them off the bike they have been really clean (compared
to pictures I've seen online) no gunk in the bowls. And barely any soot on
the butterfly sides. Bowls also don't leak if I forget to turn the fuel off, if that matters any. It's a DOHC and I removed the SOS and have capped that
off (which I've replaced again will troubleshooting my issue).

I rebuilt the carbs a little over a year ago with a Randakk kit, using a carb rebuild guide either from here or another forum that was step by step dummy guide. The bike rode good and then has been slowly progressing to this point now. Back when I bought the bike it use to stall at a stop which made me look into the rebuild and
Syncing the carbs.

[TOOLS1]

Look for the pilot jets to be plugged. It does not take much to plug them.
TOOLS

[anthony8488]

Carbs came off the bike, through look over, everything looked clean but made sure on the all the jets, buttoned back up back on the bike still nothing on 2-3 cylinders.

So thinking its electrical still, pulled the pulser generator cover off and did the inspection from the manual (17-4 / pg 232) and I get spark and can hear the coil whine a bit on 1-4. No whine, no spark for 2-3.

So guessing this is telling me the pulser generator is bad, but wanted to see if there is anything I need to check before buying another one.

I had looked into a Dyna's  ignition before and couldn't find one for my model (82 cb750sc) when I reached out to them their response was they don't have one for my model, because the rotor is more of an egg shape on mine vs circle. So what options would I have? I would like new but if chancing a used one is all I have then so be it.

[anthony8488]

So after my last find with the Pulse generator I was able to source a used one for 40 bucks, got that swapped over did the same test as the manual and saw spark on both coils and could hear the coils getting power/whine.

How important is the rubber boot cover for the small lead that screws in under the carbs from the pulse generator cable? My original one was on it but pretty dry rotted away and the used one was even worse and basically flaked apart touching it. So currently I have no boot on that lead.

So its all buttoned up now turns right over with a blip of the start button, idles good, just have to take it down the road when I get a chance. So without the road test I am at least back to where I was a couple months ago.

Also while messing with it in the garage (on the center stand)found out that my clutch cable was still engaging enough with the level pulled in that if I stopped the rear tire in gear the bike stalled out. So adjusted that to where it doesn't stall when braking the rear tire. Which most times when I rode it before I would set it to neutral before the actual stop did have occasional stalls at stops so hoping to have fixed that as well.

Just wanted to keep this updated.

[TOOLS1]

When I have a boot that goes bad like that, I just seal the wire in the opening with black RTV.
TOOLS

[anthony8488]

So almost a year later and the bike is still running strong. Nothing more then routine maintenance since the pulse generator, which I had updated most of the electric in my journey to finding out the pulse generator was what I needed  .