Topic: hesitancy at 3-5k RPM CB550

[knudsenuk]

Can anyone relate to this problem. The bike won't pull cleanly from 3-5k when warmed up. The problem is not noticable from cold, but becomes more and more obvious as the machine warms up. Culminates in stuttering, but still goes well above 5k. The bike also won't tick over on the same tick-over setting cold as when hot, i.e. I have to adjust the tick over up when cold and back down when hot. Also won't run on the choke for long (less than a minute from cold). Any help would be much appreciated.

Thanks

Richard

[Harry]

...and check the ignition and carb FAQs at the same time. Let us know how you get on...

[TwoTired]

Note that performance issues should only be addressed AFTER doing a complete and thorough major tuneup.
This means plugs (at least verify correct numbers, look at condition, and set proper gap)
Points gap or dwell adjust
Spark Timing  - static, and when on the advance
Cam chain tension
Tappet clearance adjust.
Air fliter - clean or replace.

Further, a compression check would determine if there are possible issues with engine cylinder mechanical integrity.

All of the above should be done before doing things to the carburetion, which some of your reported symptoms may point to.

Lastly, there are differences between models of the CB550.  Be sure to state what year and model you have.  And, tell us about changes made to it from stock form, I.E. exhaust system, air filter, etc.

Let's see, that should cover the first twenty questions...

We're here to help!

Cheers,

[knudsenuk]

Thanks for the advice so far. Here's what I've found. Plugs 2,3,4 furred up with black soot. number 1 about right. Noticed the choke linkage was slightl;y loose from number 2 carb onwards, corrected this - no fix. Gapped the plugs to 6mm. Points/contacts to .4mm.  Done valve clearances. Now its much worse!

[thomas evensen]

Did you adjust the ignition timing after adjusting the points?
The timing naturally gets screwed up when adjusting point gap.

I would recommend using a strope-light for ignition timing. Using
the static method gives no good results.

Thomas

[knudsenuk]

NB Won't start without the battery

[TwoTired]

I would recommend using a strope-light for ignition timing. Using
the static method gives no good results.

Thomas

Why would you say that?  It is a clearly described procedure in the Honda shop manual,  And, it's worked well for me in the 30 years I've employed it.

[knudsenuk]

Guys

I'm sure this bike should start without a battery, can you confirm. If so I'm guessing the generator is U/S, most likely a short. If the ignition coils are in series this would explain the soot deposits on no's 2,3,4 cyclinders as the spark gets weaker and weaker away from number 1 cylinder.

[thomas evensen]

I would recommend using a strope-light for ignition timing. Using
the static method gives no good results.

Thomas

Why would you say that?  It is a clearly described procedure in the Honda shop manual,  And, it's worked well for me in the 30 years I've employed it.

I used the static method first, after having rebuilt my engine, just to get it started. Using the strobe
afterwards showed that the timing was not perfect, even though I had used much effort to time it statically.
The strobe shows the exact timing when the engine is running - the static method does not. I do not know
the effect of the small difference in timing.

Thomas

[knudsenuk]

I dont think this is a timing issue, because its seems to be sporadic, it may help to get the timing spot on in time but right now the answer I need is will this bike run without a battery connected (ie. off the generator alone) if not maybe its the timing, if it should then the problem is due to a weak spark getting worse as the battery discharges...

[Gordon]

but right now the answer I need is will this bike run without a battery connected (ie. off the generator alone)

No, it will not run without the battery.

[Dennis]

No battery, NO SPARK!!
That simple.

[TwoTired]

This SOHC4 alternator needs a magnetic field, excited by the battery, to make any power.  Even then it needs 800 RPM, or so, to make enough power to run coils.  This assumes all other electrical loads are disengaged; like lighting.
No battery=no voltage=no spark.

[knudsenuk]

I can't see the point in the lick start then! Anyway, I have just stripped down the carbs and I think that there is no o ring between the main jets and the emulsion tubes, my wonderful (not) clymer manual shows an o ring. Otherwise I would assume that fuel would by-pass the jet altogether.......

[bryanj]

Yes there should be an "O" ring and as its a weird size you will probably have to get repair kits to get it. Also the kick start is there for cold weather and if the battery is down in voltage but the battery must have something or no spark

[knudsenuk]

Thanks for that.

This will most likely be the poblem I have then. Its clear that the jet is not sealing in the tube where it is located, so this has hopefully identified my problem, hence the very rich running and hesitancy....Thanks all for now - Rik

[TwoTired]

Looking back over the posts in this thread, I can't see any mention of what year this bike is.  If it's a 77 or 78 carb bank the main jet is screw in type and doesn't need o-rings.  The clymer doesn't cover this model.

[knudsenuk]

Its a 77. The jets are (I assume) supposed to be a push fit with a kind of leaf spring affair to hold them in place. What do you mean by a carb bank?....

[TwoTired]

A carb bank is the assembly of four carburetors.

The 77 and 78 CB550K carbs are quite different than those of previous models.  The main jet is a screw in type.  And, no o-ring in used.  The pilot or idle jet is pressed into the carb body as is the float valve seat.  The fine tune idle mixture screw appears to have a small o-ring under the washer a spring.  These carbs have a choke system operated by a cable and knob at the handle bars.  The clymer has no data for these carbs.

The 77 CB550F has a carb design similar to the years prior.  The main jet is held in by a spring clip and it DOES have an o-ring.  The idle or slow jet screws into the carb body.  The float valve seat also has an oring.  The choke is actuated by a lever at the left end of the carb bank.  The clymer illustrates these carbs.

In order to get meaningful information from us, you need to be specific about what model bike you have.  Otherwise, it is just flail for all of us.

Cheers,

[knudsenuk]

Its an F. The Clymer shows a main jet and an o-ring, its a low res drawing and I can't determine if the main jet has its own o-ring/seal and an additional o-ring that goes above the jet, you'll see what I mean if you look at the illustration. Ayway the o-rings around the main jets are perished and do not seal/seat tightly into the tube and if there is supposed to be an additional o-ring that goes above the jet - there sure as hell isn't on my bike!!

[TwoTired]

There is only one o-ring on the main jet to seal against the body.  The spring clip is the jet retainer.