Topic: 1976 550K + 087A carbs = trouble

[TwoTired]

I have all three US models of CB550F.  They all use the same engine (functionally), same exhaust, same carbs, and same induction pieces.

My F2 "feels" like it has more power than either the F0 or F1.  They are all very close in how they perform.

Perhaps the test model itself was changed between reporting cycles?

Cheers,

[Deltarider]

and same induction pieces.

Parts numbers tell they've been modified.
Could it be that the F2 had to comply with new emission rules? After all the F2 was launched in the same time the K3 came on the market.
Were the needles of the F2 in the same slot as the F/F1?

[TwoTired]

and same induction pieces.

Parts numbers tell they've been modified.

Or from a different vendor, or used a different mold material. Or...?
What specific part descriptors are you referring to?

Could it be that the F2 had to comply with new emission rules?

Can't deny a possibility.  I don't see what changed, though.

After all the F2 was launched in the same time the K3 came on the market.

True, I can't explain that with any facts.

Could be time line interactive.
The F exhaust is more restrictive than the early K models, and this allowed leaner settings for carb set ups.  I speculate that the emissions were lower for the F model vs, the K model until 77, when the exhaust and carbs changed for the K.

Working toward an emission limit, the bar war was progressively raised by the EPA.  The 77 K Model needed different exhaust and carbs, to get under the bar for 77 and 78, while the F2 squeaked under the bar for 77, and was discontinued before 78.

Were the needles of the F2 in the same slot as the F/F1?

Yes.  As far as I can recall.  If it used the stock exhaust and induction, the stock carb settings were the same among all the CB550Fs.

Cheers,

[gregk]

My most recent move has been to get 'professional help".  Not that there isn't quality help on the forum, but I wanted confirmation that the 3000 mile tune up settings that i was using were correct.  Took the bike to a Honda trained mechanic and he went thru the tune up procedure and confirmed that all were correct.  He also took the carbs apart and could not find anything wrong.  The compression test indicated two low cylinders and he also noted that the vaccuum was low. 
He suspect that the rings are stuck on the pistons.  I took the bike out last nite and gave it a run down the road.  After about 10 miles the plugs are fouled and I was barely able to make it back home. 
My next move is to take the head off and inspect the cylinders and rings.  This sounds like a winter project! 

[Nortstudio]

Bummer!  So sorry to hear about that Greg.  I am going to get back into my carb tests today - first day I have had a chance this week.  Hopefully I have better luck.  I'll be keeping an eye on your progress, and hope that comes as soon and painlessly as possible.

Scott

[Duanob]

My most recent move has been to get 'professional help".  Not that there isn't quality help on the forum, but I wanted confirmation that the 3000 mile tune up settings that i was using were correct.  Took the bike to a Honda trained mechanic and he went thru the tune up procedure and confirmed that all were correct.  He also took the carbs apart and could not find anything wrong.  The compression test indicated two low cylinders and he also noted that the vaccuum was low. 
He suspect that the rings are stuck on the pistons.  I took the bike out last nite and gave it a run down the road.  After about 10 miles the plugs are fouled and I was barely able to make it back home. 
My next move is to take the head off and inspect the cylinders and rings.  This sounds like a winter project!

How were they fouled? Oil? Gas? Carbon/Soot?

[gregk]

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How were they fouled? Oil? Gas? Carbon/Soot?

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The plugs get fouled with carbon/soot.  They are always dry to the touch.  It takes about 5 miles to foul them.  After that its a bit of a trial to get the bike home without pulling the plugs and cleaning them.

[Duanob]

How were they fouled? Oil? Gas? Carbon/Soot?


The plugs get fouled with carbon/soot.  They are always dry to the touch.  It takes about 5 miles to foul them.  After that its a bit of a trial to get the bike home without pulling the plugs and cleaning them.

then it's not oil bypassing the rings, it's still something to do with your carb set up. Have you checked your needles and jets? I had some crud on the needles about where they would seat into the jet. It was enough to keep the Needle jets from closing off the fuel getting into the carbs at idle. Driving around town it was enough to foul and carbon up the plugs in a short time. Even hiway driving the plugs were always black. I used a 0000 steel wool to clean them up and cleaned the jets as well with simple green. My plugs don't get carbon fouled anymore. The bike is a lot smoother through the entire RPM range.

If the needles are clean you can always drop them down into the seat one notch. According to the carb manual this may be necessary if the needles and jets get worn over time and they don't close off all the way. Don't forget to re-sync your carbs after messing with the needles.

[chrima]

I'll just throw this out there in case it might help. I am far from an expert, but I have the same year motor (in a 77 550k) with the same carbs.

After a full carb rebuild, I had it running, but very rough and the plugs would get very sooty like it was running real rich. I noticed alot of exaust leaks around where the pipes mount to the motor. I ordered new copper exhaust gaskets, synched the pipes down real good and now it runs really nice.

Anyway, hope you get this figured out.