Topic: CB550K3 - What Could the Problem Be?

[K3Owner]

Hi all,
Maybe y'all can help me troubleshoot. I'll tell you what's up.

A coil would quit when hot last summer so I replaced both with EMGO units. After that, installed a DynaS ignition trigger. I know, more later. Last, the #4 plug cap was intermittent so I just replaced all 4 with OEM units.

Took a 90 mile super slab trip to Stone Mountain and back yesterday and she ran great. 1/2 mile from the house, pulling out of an intersection, she fell flat on acceleration. I figured it was empty but a full tank made no difference. Sounded like a cylinder dropped out - not as bad as an ignition issue where two cylinders drop.

Today: Pulled #4 wire, accelerated, and no difference. Pulled #2, same. I'd expect it would have showed itself with that. Pulled the plugs and all looked good - dry and a little on the rich side - not fouled. All the DynaS comments still had me wanting to eliminate it from the equation so the points are now back in. No change.

I checked the wiring to the coils with the ohmeter. All OK.

She never idled well. I had D7EA plugs in it and she takes D7ES. Reaches farther into the chamber. Sweet idle now! OK, on to the carbs, yes?

Hoping to get Godzilla out to Birmingham tomorrow so up at 4 to sort through the carbs. Tell me what I've missed. I've been through the carbs recently so it's frustrating.

[scottly]

If the Dyna, or points, or coils were the problem, the two cylinders affected would be 1-4 or 2-3. You ran the bike on reserve for a length of time, which may have allowed any debris at the very bottom of the tank to get into things? Pics of all 4 plugs might help.

[Vinhead1957]

I with the bad gas crap theory check the strainer on the gas petcock

[Stev-o]

+1 check fuel flow out of petcock.

[K3Owner]

Gotcha. I had a spare filter on the line (now removed) so it was double filtered but who knows? I'll check the petcock while the tank is out and can't wait to see the mains.

As for the plugs, #3 was the only one that looked lean. Insulator clean and white on one side and gray on the other. I chopped the plugs right after a full throttle effort hoping to see something.

Brewing coffee and then to the basement for some carb work. Stay tuned.

[K3Owner]

Carbs off. Tank still draining. I did find that #1 main had significantly unscrewed at the emulsion tube. Perhaps this is the reason for the flatness? Certainly would richen the heck out of it but the plug looked OK on #1. Everything else about the carbs looks very good. All mains clean. I'll clean again and will blow air through them.

I can admit here that inexperience got the best of me many years ago when I screwed the tubes in too far. Ended up with a 4,000 RPM idle and tubes that no longer tighten where they should. I used a nylon nut to shore them up. Bad on me. I have a second good set that I might use.

I used the circular gaskets from the Vesra? kit for the top end rebuild and they're lousy. Anyone have a tip on replacements? My son got a nice set of 4 off fleaBay for his KZ for $20 so I'll look there first. That would be a nice find. The o-rings require sealant to keep them in place for mounting and it can't help but get in the bowls.

Not riding today...

[Stev-o]

Loose jet could cause an issue and leave the online filter off, too.
Make sure fuel lines are as vertical as possible too, remember, carbs are gravity fed. 
Bet you do not find major issue, just a couple minor ones, enough for it not to run great.
Good luck

[K3Owner]

Thanks Stev-o. I found some gaskets. The bowls were clean three months ago but the gasket cement used to form the o-rings in their place was attacked by today's wonderful gasoline and the bowls were cruddy. Amazing. Everything else clean. I'll handle the screen in the tank this afternoon. I've got an old Ford diesel tractor to rewire first 

[flybox1]

while you're tackling your carbs, might as well include cleaning your tank.  check for rust in the bottom or a lining deciding to quit on you.
white vinegar (few days) or prep-n-etch (1 hour) are great, inexpensive de-rusters.
that gasket cement is crap.  do your best to get it all off the first time or it will haunt your carbs and get the formed bowl gaskets.

[K3Owner]

Exactly. Draining it after a fill-up has taken some time but I'll flush it out and will clean the screen. Have a great weekend!

[Stev-o]

Agree with fly, no gasket cement.