Topic: Help, stumped - 76 CB550F idles OK, over 3k RPM stumbles, sputters, backfires

[Sable]

Carbs fresh off and opened.

[Sable]

Soooo....turns out these are 100 jets and the stock were 98. Swapped back to the stock 98s. Stock everything except O-rings for that matter. Get her back together. Fire her up. Same crap.

Its dark out....so I noticed something this time. When it starts acting up the lights start diming in and out pretty dramatically. I just put this battery in so I can't see it being that. But could it be the regulator taking a dump and causing all my issues? Really think this may be electrical now.

[paul_D]

Hondaman said maybe the intake runner seals are all in need of replacement on my forum, perhaps you should look into changing them as well. I am going to later.

[TwoTired]

Really think this may be electrical now.

Good luck with that.

[Sable]

Taking a break to gather my thoughts on it.

[Sable]

Bit the bullet and found a retired mechanic I trust. Will post the results when I get them. Diagnoses at a glance was a condenser issue but no formal diagnoses has been done yet. He is going to go over everything before he makes any assumptions.

I'm still going with condenser and/or rectifier issue. Running rich and idle air doesn't adjust enough to lean it out. Floats maybe but I checked them so many times. Hope he solves it.

[Sable]

Diagnoses is in.

1. Floats way too high. (I must be an idiot as I checked them four times with the special float tool.)

2. Carbs where way out of sync. I knew they would be but not to the degree they ended up being.

3. Points acting up. A Dyna S ignition has been installed.

I've been told she is running very strong now. Excited to pick her up. Yet at the same time I am baffled that I was so bad at trying to remedy this. Guess I should stick to what I know leave these classics to all you pros.

Thank you to everyone who attempted to help me. Wish I had been a better student.

[Duanob]

Third time is a charm! Keep us posted on how she runs when you get it back. It takes time and patience to figure these things out but once you do you won't have to take it to a mechanic. Sometimes its even fun to wrench on them.

I have a twin of your bike I'm going to jump on tonight for a spin. The sun finally came out around here!

[Sable]

Rode it home from the shop last night. She is running really well now. Good strong idle.
Valves were checked and adjusted to spec. Compression was also checked. Guess #4 is showing 100lbs cold but goes up to 120lbs when warm. Will need to keep an eye on that. The new dyna ignition seems nice so far. Consistent through the Rpms. No longer any kind of hesitation or break up. Carbs are synced. I was told it was as much as 8cm off. Seems to be running very nice now.

I need to get it out and put some miles on it. The ride home was 7 miles of horrible stop and go city traffic. Need to get it out and stretch old girls legs. See how she does.

I just put a new battery in it a few months ago. Its already acting up and doesn't seem to hold a solid enough charge to run the starter. Think I may still need to look into my rectifier/regulator. That will be my next adventure after I recoup from this one. Damn money tree shed its leafs for the year. Just glad I have a bike to ride again.

[TwoTired]

The Dyna-s ignition makes whatever coils you have consume almost twice the power as points.
The alternator doesn't charge the battery at idle.  So, the battery depletes during idle.  If you keep the Dyna-s and do a lot of city-idle operation, better get yourself a charging tender for when parked.

[Bankerdanny]

Honda float needles or aftermarket needles?

The quality on aftermarket needles is very suspect. If you have the originals I would compare them to the new ones to make sure they are the same size. I would also test to see if the plunger on the old needles still moves freely, and if it does I would re-install the old originals, reset the float height and see what happens.

[lucky]

Soooo....turns out these are 100 jets and the stock were 98. Swapped back to the stock 98s. Stock everything except O-rings for that matter. Get her back together. Fire her up. Same crap.

Its dark out....so I noticed something this time. When it starts acting up the lights start diming in and out pretty dramatically. I just put this battery in so I can't see it being that. But could it be the regulator taking a dump and causing all my issues? Really think this may be electrical now.

Changing the main jets from 100 to 98's would not make much difference since we don't ride around at full throttle most of the time.

When it is completely dark and the bike is running is also a good time to see if your spark plug wires are arcing to ground. Means the insulation is broken down.

[Sable]

She is 100% back to bone stock carb parts. Original jets from the day she was assembled back 36 years ago.

The battery issue I speak of has long plagued this bike since I took ownership of it 17 or so years ago. I have always just thrown it on a trickle charger every now and then to work around the issue. I haven't ridden with the dyna installed other than home 7 miles from the shop. Can't speak to that yet. Maybe I just need to buy better batteries?

I can charge the battery up but it loses its cranking power fast. We put one of the shop batteries onit to see if any difference and it was night and day. Would crank for a long time before losing power. Thus seemed like it was a good possibility that perhaps the charging system may be quality here. Just a thought. Different subject for a new thread though.