Topic: 1976 Honda CB550F with less than 5k miles

[Pedrobabone]

Help!
I have a completely stock 76Honda CB550F with the Keihin 087A's on it and an having a time getting it tuned.
The symptoms are, in consistent idle, when revved will sit at 2k rpm a bit too long before going back down to the inconsistent idle.
What I have done, rebuilt the carbs (main jet 100, pilot jet 38 and needle on the 3rd notch from the top) set float height (clear tube in float bowl method), adjusted valves, new spark plugs for the 5th time, checked points and set timing.
There has to be something I am over looking. Any help would be greatly appreciated.

[Ryan66]

I dont see anything about a bench sync or vacuum sync. Have you done either?

[Stev-o]

I have a completely stock 76Honda CB550F with the Keihin 087A's on it...

I dont think you do.  My completely stock '76 CB550F has Keihin 069 carbs.

Do you have the airbox and original 4 into 1 exhaust?  Main jet should be #98 if you do

PS.  Are they genuine Keihin jets?

[seanbarney41]

Symptoms often indicate a vacuum leak, or running lean, or weak timing advance springs, ...could even be a sticky throttle, throttle cable, or too tightly adjusted push/pull throttle cables

[Little_Phil]

I have a completely stock 76Honda CB550F with the Keihin 087A's on it...

I dont think you do.  My completely stock '76 CB550F has Keihin 069 carbs.

He may have it wrong and mean 76 550F(our)

[Deltarider]

Do yourself a favor and identify your model first. You can do that by comparing the engine- and framenumber of yours to those listed in the first 4 pages of the CB550 Parts Lists. They are all here: http://www.honda4fun.com/materiale-documentazione-tecnica/parts-list/parts-list-cb550 A proper identification will reward you with the correct info on: parts, colour codes, 'area codes' and what number carbs your model originally had.
087A carbs were exclusively fitted on the CB550K2. I hope you have not replaced any of the brass parts; they hardly wear if at all. For those worried about correct fuel levels in the float bowls, here is an easy test which can save a lot of trouble. http://forums.sohc4.net/index.php/topic,185754.msg2151647.html#msg2151647.

[StockRider]

I have a completely stock 76Honda CB550F with the Keihin 087A's on it...

I dont think you do.  My completely stock '76 CB550F has Keihin 069 carbs.

He may have it wrong and mean 76 550F(our)

76 CB550K would have had 087A's originally.

https://motorcycleproject.com/text/specs.html

[Pedrobabone]

Sorry guys StockRider is correct, it is the CB550K'76 (CB550four).

I got this bike from the original owners son who had rebuilt the carbs before I got it, there is no telling what he replaced. I have gotten 3 different rebuild kits and a set of 98 main and 35, 40 pilot to try and balance out the fouling of the plugs with no good results.

Ryan66, I have bench and vacuum synced the carbs.

I took the carbs off again last night to see if there was anything obvious for the idle issue and put it back together and it resolved it self (probably vacuum leak).
I still have yet to figure out the almost instant fouling of the plugs and the choke does not work. I can confirm the carb is clean.

Deltarider, I will try the float bowl drain and measure technique.

Thanks

[69cb750]

If the plugs are black the carb is feeding to much gas.
Check choke opens and closes, check air cleaner clean.

[Pedrobabone]

The choke butterflies open and close as they should and even with the air filter out it runs rich.

I just switch back to 98 main with a different needle from one of the 3 kits I have and the bike seems much happier but, I am out of spark plugs to foul so, I will just ride it as it is and test with new plugs when they arrive.

[Deltarider]

Without having read all the above, are you sure the little O-rings around the main jets are OK and seal well?

[Pedrobabone]

I am not entirely sure on how to test if the O-rings on the main jets are sealing well but, I cant imagine that out of the 3 kits that I have tired that all O-rings are bad. All the kits that I have tried use 100 main jets.

When I use 100 main jets it sounds like a boat and billows out white smoke that smells like gasoline.

[Deltarider]

Are you sure about the gasoline? I mean: how old is it? Any water?

[Pedrobabone]

The oldest gas I have put in it is 2 weeks old and no water.

[Scott S]

 Did you check the needle clip positions?

 The O rings on the main jets should be fairly snug.

[Scott S]

 And I haven't seen any mention of the mixture screw setting.

[Pedrobabone]

I think I originally said the needle clip was on the 3rd notch but, its actually on the 2nd notch. Where the clip is supposed to be I have no idea and I have tried everything from the 4th notch to the 1st notch.

The main jets do not fall out and require a decent tug to pull them out.

Mixture screws are 1 full turn and 1 half turn out, I have tried these all the way in and all the way out to see how it would effect the mix but they did nothing.

[Stev-o]

Keihin 087A's on it...

PS.  Are they genuine Keihin jets?

Aftermarket jets cause tuning problems.

[Pedrobabone]

None of the jets have the Keihin "K" on them. Ordering genuine Keihin jets now. Does anyone know the needle that goes in these carbs? I don't think anything is stock in these carbs.

[Deltarider]

Does anyone know the needle that goes in these carbs?

Consult the overview I have composed years ago. OEM needles will have a 6 digit stamped in number. You cannot order them seperately;  they come as a 'jet needle set'. I don't know if they're still available. I strongly advise CB500/550 owners NOT to abandon their original brassware. I did not have to replace any of them.