Topic: '75 CB550 Roll-on delay

[sniper1]

I have noticed that when riding, particularly when engine gets hot, that when I roll on the throttle, there is a slight delay in response in acceleration. It is about 1-2 seconds. It is not smooth at all and when it "kicks in" it really kicks in. I notice it more when exiting a corner coming from rolling off the throttle to rolling on. It happens on straightaways also, so leaning the bike over has nothing to do with it. The throttle cables are tight, valves are adjusted properly and timing is good.  I synched the carbs a few months ago.

So, any ideas??

[Duanob]

Running rich? Lean? That makes a difference especially in these 550s. Clean the pilot jets lately?

[hereforever23]

When you say the throttle cables are tight, what do you mean?  There should a little bit of play such that you can roll the throttle slightly before you feel any friction.

Are the jets stock, floats set at the correct height, and air screws set at the correct setting?  What do your plugs look like?

[flybox1]

Running rich? Lean? That makes a difference especially in these 550s. Clean the pilot jets lately?

+1
Pilots, and emulsions.

are you 'rolling-on' from 3000rpm, or 6000rpm?

[gregripko]

I have this issue as well....when the engine is cold it rolls on smooth but when it warms up i notice a blubber if i crack the throttle too quickly....i have to give it like 1/2 throttle with careful clutch control to get it rolling without it sorta blubbering......smooth riding beyond that..... running air box (uni foam filter) with 100 mains and 40 slows....thinking if changing them out for the 38s i have to see if that helps....

[mono]

I have this issue as well....when the engine is cold it rolls on smooth but when it warms up i notice a blubber if i crack the throttle too quickly....i have to give it like 1/2 throttle with careful clutch control to get it rolling without it sorta blubbering..... running air box with 100 mains and 40 slows....thinking if changing them out for the 38s i have to see if that helps....

I've got 100s and 38s, and don't have that problem.  air screws are out a little extra (i forget how many turns total offhand).

if i really lay on it, there's always a hesitation, but 1-2 seconds seems realllllly long.  i would say +1 to cleaning.

sniper - how hard are you cranking the throttle when this happens?

[Bru-tom]

^^^^
id appreciate if you could check how many turns out yours is set to mate trying my luck here, hehe

[TwoTired]

It matters if the induction and exhaust are stock or modified.  Care to share that info?

Tell us where the pilot screws are set, and which model carbs are on the bike.

Mark your throttle and tell us what the throttle position is when the problem occurs.  RPM indication would be nice, too.

Are all the spark plugs showing the same deposit pattern?

What IS the deposit pattern?

Now many decades ago was the last complete 3000 miles tune up check list performed?

Do you know what the float height setting is?

[gregripko]

My exhaust is 4 into 1 Mac.... 3000 mile was done a couple months ago....put on about 1000 miles... occurs mainly at a dead stop to acceleration...1/8 of a throttle crack creates a blubber that clears with more throttle....a quick crack of throttle and it sounds like engine is going to die (but it doesnt)....ONLY occurs when warm....if it were a clogged jet or emulsion tube i would imagine that it would occur cold and warm....or any time for that matter...maybe i'm wrong

[TwoTired]

My exhaust is 4 into 1 Mac.... 3000 mile was done a couple months ago....put on about 1000 miles... occurs mainly at a dead stop to acceleration...1/8 of a throttle crack creates a blubber that clears with more throttle....a quick crack of throttle and it sounds like engine is going to die (but it doesnt)....

Did it behave the same immediately after the tune up?
Are the spark plugs sooty?  If so, it is too rich in the throttle position before you crack the throttle.  Everything beside exhaust stock?  Does the mac still have it's baffle?

Is your bike also a 75 CB550K with 022a carbs or a 75 CB550F with 069a carbs?  Not sure what the O.P. has.

[mono]

^^^^
id appreciate if you could check how many turns out yours is set to mate trying my luck here, hehe

i think i have them at 1/4 turn out from factory spec (Keihin 022A carbs) -- running a Mac 4-1 with stock airbox and un-oiled foam filter.  this makes it run better on the highway once warmed up, but seems to make it a little more cold-blooded.   if i'm going to be doing a bunch of city driving (short little "low speed" bar-hopping trips) i turn them back in 1/4 turn. 

i could use some larger slow jets (40s i think), but any throttling at speed is quite responsive.

[Muckinfuss]

Generally speaking, a cold carburetor engine stumbles because it was taken off choke too soon and isn't warm enough to mix properly at the intake.  A hot carbed engine stumbles because it's leaned out at that point.  Coming off dead stop with a warm/hot engine with stumble would indicate to me your idle mix is off.    Above 1/4 throttle, then you may have an issue with needle wear, but all the parts really have to be working together, so as everyone else has said, float height, dirt, etc.... all can make you crazy.

[sniper1]

TT,

The plugs are a little sooty. I rebuilt the carbs last fall. I am running 38s and 100s. Screws are out 11/2 turns.
I do have about a 1/4 inch of throttle play, so the cables are adjusted properly. I notice the hesitation anywhere above 3500 rpm especially in 5th gear. Tune up was done when rebuild complete last fall (about 600+ miles ago). I rechecked valves and timing in February and all was good. Carbs have no markings other than Khein on them but assume they are 22a's. if I remember correctly, my 77 550 had the PD carbs. Float height set as per manual (22mm if I remember correctly).

Another thing now that I'm thinking about it, is that the choke doesn't seem to choke. It actually acts like its starving the carbs from fuel. There is no increase in rpm when the choke is on, it actually decreases. I simply hold the throttle so that it runs at about 2500 rpm until it warms up a bit.

Hope this provides some more info.

[sniper1]

Oh yeah, I am running a MAC 4 into 1 also. No other engine mods. Stock air box with new filter.

[TwoTired]

Ok sniper,
 Check this chart and relate what the plugs look like.  It depends on where the soot deposits are on the plug, as the outer ring should be black pretty much all the time.
http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

You might consider doing a plug chop on clean plugs after some operation in the RPM/throttle position where you notice the problem.

Do you recall where the slide needle is adjusted?  Which clip position?

Are you using ethanol blended gasoline?

Does the MAC have a baffle?

The choke on the 022A carb has no fast idle cam linked to it, like the PD carbs do.  Choke, therefore does not advance RPM for you.  You have to do that with the twist grip during warm up.  If you are using D7EA heat range plugs you do not need a stationary warm up.  You can drive with the choke partially on and gradually take it off during the warm up period.
The choke restricts incoming air and forces the jets to produce more fuel in ratio.  This tends to lower RPM from the natural free breathing state.

Take a look at the carb body mount flange, top right side.  That is where the set up number is stamped.

About the behavior.  After the delay occurs, does it burble back to life, or come back cleanly, resuming operation like nothing was ever wrong.  The former means it was too rich to fire, the latter means it was too lean to fire.

These carbs do not know about RPM.  They respond to throttle position.  And 3500 RPM can be many throttle positions as the RPM is dominated by load conditions.  If a carb mixture correction is going to attempted, one must know where the slides were placed before and during the problem.  Mark your throttle, so you can report this position along with RPM info.

[gregripko]

022a Carbs on a cb550K....plugs a bit sooty...i'll have to get back to you on the air screws....baffle still in the exhaust.....when its cold it goes from idle to rolling no problem....seems to make it worse when i open and close the throttle quickly...like a half second....it just stumbles a bit...but a half throttle roll with careful clutch release and it's off to a good rolling start....

[sniper1]

TT,

Based on the chart, plugs are definitely #3 just not quite as bad. Not oily, just sooty.

If my memory is correct the needle was in the stock position, which is #2 I think.

Yes, ethanol blended gas. Its the only thing we can get around here. Sucks!

Mac exhaust has baffle inserted but drilled out on the outer edges. 6  1/4" holes drilled in. (not by me, but from guy I bought system from). Sounds OK, but not sure if that effects anything.

After the delay occurs, it seems to come back cleanly, but rather suddenly, resuming operation like nothing was ever wrong.  It is really noticeable when I roll the throttle off for some reason like slowing down for a corner, then when I roll the throttle back on, the delay happens, and then it just takes off. If I'm just cruising at say 55 mph with steady throttle and then open her up, sometimes there is a delay before it accelerates and sometimes it just accelerates with no issue. Not sure what to make of it.

"These carbs do not know about RPM.  They respond to throttle position.  And 3500 RPM can be many throttle positions as the RPM is dominated by load conditions." - This makes complete sense to me. The variable obviously being the load condition which can include many factors (temp, humidity, uphill, downhill, etc.).

"If a carb mixture correction is going to attempted, one must know where the slides were placed before and during the problem.  Mark your throttle, so you can report this position along with RPM info." - How is this done? In order to make a correction, the carbs have to be off, so how would I be able to replicate this with the carbs off?


Gregripko,

Sounds like we have similar issues with our '75's.

TT is the without a doubt the expert on these things, and as always, I will certainly follow his advice, he has helped me out before.

[TwoTired]

022a Carbs on a cb550K....plugs a bit sooty...i'll have to get back to you on the air screws....baffle still in the exhaust.....when its cold it goes from idle to rolling no problem....seems to make it worse when i open and close the throttle quickly...like a half second....it just stumbles a bit...but a half throttle roll with careful clutch release and it's off to a good rolling start....

It's important to know where they are sooty.  Can you make a comparison to the spark plug chart I posted?  Also, state if the deposits are from general running, or a plug chop from a known, consistent throttle position.
Please state if all 4 plugs show the exact same deposit pattern.

I'll ask the same about how the bike recovers from stumble.

About the behavior.  After the delay occurs, does it burble back to life, or come back cleanly, resuming operation like nothing was ever wrong.  The former means it was too rich to fire, the latter means it was too lean to fire.

If it runs ok cold, then it is likely that the mixtures are too rich, at least at some throttle position.  However, you must realize that you determine which metering device in the carb is dominant, with your twist grip setting.  This is information that must be weighed for a diagnosis.

Your last statement makes me wonder if you are expecting more torque from the engine than it has to give.
Are you slipping the clutch during take off,  or engaging and twisting the throttle?  They don't have much torque from down low in the RPM band.  But from idle and gear engaged the bike should respond willingly if a bit lethargic, with up to 1/2 remaining throttle twist.

Diagnosing two bikes in the same thread is rather confusing.  And I am having a hard time keeping bike configuration details straight.  Might be best to state configuration and bike model details with your response.

[TwoTired]

Based on the chart, plugs are definitely #3 just not quite as bad. Not oily, just sooty.

Is this from general, all-throttle position operation or from a set throttle position?

If my memory is correct the needle was in the stock position, which is #2 I think.

I'd expect that to be too lean for a stock Cb550 with 022a carbs.  Stock needle position is 4th groove from top, (which pulls the needle out of the jet allowing more fuel to pass).  Did I already ask if these are the stock slide needles, or aftermarket?

Mac exhaust has baffle inserted but drilled out on the outer edges. 6  1/4" holes drilled in. (not by me, but from guy I bought system from). Sounds OK, but not sure if that effects anything.

Probably does some. Open exhaust generally demands a bit richer fuel mixtures.

After the delay occurs, it seems to come back cleanly, but rather suddenly, resuming operation like nothing was ever wrong.  It is really noticeable when I roll the throttle off for some reason like slowing down for a corner, then when I roll the throttle back on, the delay happens, and then it just takes off. If I'm just cruising at say 55 mph with steady throttle and then open her up, sometimes there is a delay before it accelerates and sometimes it just accelerates with no issue. Not sure what to make of it.

It likely means that the fuel mixtures among the three metering devices are not well balanced.
  The delay you are experiencing reveals the mixture was too lean for the previous throttle position and doesn't blend well with the too rich throttle position you  selected for acceleration and perhaps cruise.

"If a carb mixture correction is going to attempted, one must know where the slides were placed before and during the problem.  Mark your throttle, so you can report this position along with RPM info." - How is this done? In order to make a correction, the carbs have to be off, so how would I be able to replicate this with the carbs off?

You are reporting only throttle change information, rather than from what position to what position, (perhaps 1/3 to 3/4?).  Changing the mixture inside the carbs is a corrective action.  But, before doing that we must know, which direction to change which metering device.  And that prior to action information is gleaned from knowing what the throttle positions were before during and after the problem to be addressed.  Marking the throttle is done for the testing and problem statement phase of the repair process.

Given the rich spark plug condition and your reported sooty plugs (Are all showing the same deposits?), I'll ask if both the emulsion tubes in each carb are clean and clear and that the air jets and their passageways are unrestricted?

[sniper1]

Is this from general, all-throttle position operation or from a set throttle position?

All throttle position.


I'd expect that to be too lean for a stock Cb550 with 022a carbs.  Stock needle position is 4th groove from top, (which pulls the needle out of the jet allowing more fuel to pass).  Did I already ask if these are the stock slide needles, or aftermarket?

Stock slide needles.


Probably does some. Open exhaust generally demands a bit richer fuel mixtures.

That's what i thought also.

It likely means that the fuel mixtures among the three metering devices are not well balanced.
  The delay you are experiencing reveals the mixture was too lean for the previous throttle position and doesn't blend well with the too rich throttle position you  selected for acceleration and perhaps cruise.

OK, makes sense. How does that happen?


You are reporting only throttle change information, rather than from what position to what position, (perhaps 1/3 to 3/4?).  Changing the mixture inside the carbs is a corrective action.  But, before doing that we must know, which direction to change which metering device.  And that prior to action information is gleaned from knowing what the throttle positions were before during and after the problem to be addressed.  Marking the throttle is done for the testing and problem statement phase of the repair process.

I'm not sure how I would mark the throttle while riding. I guess I can make a mental note.

Given the rich spark plug condition and your reported sooty plugs (Are all showing the same deposits?), I'll ask if both the emulsion tubes in each carb are clean and clear and that the air jets and their passageways are unrestricted?

They were when I rebuilt them last fall.

[sniper1]

Here is a pic of the plugs.

[TwoTired]

Is this from general, all-throttle position operation or from a set throttle position?

All throttle position.

Then the deposits show and average of all the throttle positions you used.

It likely means that the fuel mixtures among the three metering devices are not well balanced.
  The delay you are experiencing reveals the mixture was too lean for the previous throttle position and doesn't blend well with the too rich throttle position you  selected for acceleration and perhaps cruise.

OK, makes sense. How does that happen?

Either a fault in the carbs, or an incorrect fuel or air metering adjustment.

I'm not sure how I would mark the throttle while riding. I guess I can make a mental note.

You might try masking tape and a magic marker.

Given the rich spark plug condition and your reported sooty plugs (Are all showing the same deposits?), I'll ask if both the emulsion tubes in each carb are clean and clear and that the air jets and their passageways are unrestricted?

They were when I rebuilt them last fall.

Was the bike running better last fall?

I looked at your plug pictures.  Did you notice they don't all have the same deposit patterns?  I think you need to track down why.  I'd probably start with the 3k tune up verification, and then check vacuum sync.  You don't want to fine tune carbs to ill set tune up specs.

Could the bike have intake runner leaks?

[hereforever23]

I'd expect that to be too lean for a stock Cb550 with 022a carbs.  Stock needle position is 4th groove from top, (which pulls the needle out of the jet allowing more fuel to pass).  Did I already ask if these are the stock slide needles, or aftermarket?

Stock slide needles.

So are you confirming needle is in the stock position? 4th groove from top?

I'm not sure how I would mark the throttle while riding. I guess I can make a mental note.

Take a piece of masking or blue painter's tip and wrap it around the throttle grip.  Then take a sharpie and mark lines at closed throttle and wide open.  Then make marks at 1/2, 1/4, 3/4, 1/8, 5/8 etc.  These can be referenced against the crack in the switch assembly or use another piece of tape with a line on it

Given the rich spark plug condition and your reported sooty plugs (Are all showing the same deposits?), I'll ask if both the emulsion tubes in each carb are clean and clear and that the air jets and their passageways are unrestricted?

They were when I rebuilt them last fall.

You are using a stock filter, right? Not a UNI filter in a stock airbox?
Have you checked your petcock filter?  You might verify that one is in there...I was surprised to find the screen missing in mine when I looked.
What is your idle set at?

Your plugs have different deposits.  1 and 4 look good and maybe even 2 as well- its hard to see. 3 looks rich.  It would be easier to see them if you took a profile shot.

[sniper1]

Yup, stock needle setting #4 position.

Petcock filter in place. I put a new one on when I rebuilt it and checked it just about a month ago.

Idle set at 1200 rpm.

Stock air box and filter.

You really think those plugs look OK? They all seem pretty sooty to me. I'll pull 'me again this weekend and take some profile shots.

[new2bikes-again]

Sniper, I've got the same issue. 74 550K. Runs awesome cold. Have to know how to ride it hot . Don't worry TT, you don't have to help all three of us at once! I'll wait my turn .

Sniper, I've got 38 pilots. 100 mains. Stock needle setting. Carbs synced. Emulsifiers cleaned. Floats 22mm. Timing set. Stock air box with a foam 'some brand' air cleaner. Buying a stock one in the next few days. Pilot screws 1 1/2 out. New NGKs fixed it my first couple rides last week, but it's back. I've got tape on the grip right now, and I'm going to get OCD with my statistics before I hit TT and Lucky!

Please keep us posted. There's 3 of us on this page alone! Imagine how many we could help!