Topic: I think I'm running lean, 550f

[fastbroshi]

   Greetings everyone,

   I'm trying to get my carbs tuned just right on my '77 550F, 069A carbs.  Rebuild was done on them about 50 miles ago.  All the jets are stock, 38 pilots(idle)  and 98 mains.  I have yet to sync them with any type of guage, but it is pretty close as I can get it to idle pretty well at about 14-1600 RPM.   Making things more difficult, the temperature here in Texas dropped today and it's probably going to stay that way for a while.  Floats were set at around 22mm.
  I recently adjusted the valves and cam chain slack, checked the points' gap, timing (dynamic and static), changed the oil, recent plugs w/ correct gap. 
  I'm running a Uni filter, oiled well, and the stock 4-1 albeit with the baffle removed.  The header gaskets are new.  Carb boots are verified tight.  Also, when I had the carbs off to rebuild I smoothed out the intake runners a bit, careful to remove a minimum of material (new gaskets on these).
  What exactly is the correct number of turns out on the Idle Mixture Screws for these?  I thought it was 1 or 1 1/8.  I initially set it at this, but there was a little of popping out the exhaust at idle.  After adjusting to about 3 the popping has went away from the rev range.  This tells me turning these screws out enrichens the mixture correct?  When I did my initial IMS setting it was about 80-85F. 
  Until today, currently about 55 degrees F outside.  In first gear there seems to be a bit more hesitation/bogging right off idle under load low in the RPM range.  Note: before adjusting my timing (which was WAY advanced), this bog right off idle wasn't there.  And I'm not sure, but I think it may be popping a bit when rolling off the throttle quickly at speed.  Kinda hard to tell w/ the helmet is on.
  After my ride today, I put the kickstand down at took my helmet off to listen, and I can hear no popping, though it might be there, barely perceptible.  Maybe just the carb sync?
  And it's so recent after my rebuild that it hasn't had the chance to blue or yellow the pipes at all.
  Since I do have an idea what's going on and I think it's real close, I haven't done any plug chops. 
Also, choke at idle will kill it.  I have yet to observe any fuel mileage.
I'm thinking I need to go up a size or two on the idle jets.
  I want to take the easiest observations first.  I'm thinking:

1.  Do the with and w/o filter test.

  What next?  Input please.

[TwoTired]

You're trying to fine tune carbs without doing a carb sync?  Good luck with that!  (a phrase about cross purposes comes to mind.  )

With no baffle in the muffler, your back pressure is way lower than stock.
I wouldn't expect a 98 main to be large enough, as more oxygen should be available during each cycle. 
I'd probably guess that K model settings (main AND throttle valve) would be more appropriate.  But, I'd sure look at spark plug deposits before I made changes.  (and verify that all cylinders were operating with the same flavor deposits.)

As for popping in the exhaust...  Are you sure the exhaust gaskets aren't leaking?  Otherwise, I'd guess that your idle mixture (if you can call it that at 1400-1600, as your slides are open enough to start drawing from the throttle valves) is too lean.  A cylinder (or two) that doesn't fire or misses a cycle (because it was too lean) tosses the unburnt charge into the collector along with another and gets ignited there, from another cylinder's hot discharge)

If the popping is back through the carbs it's a lean mixture, leaking intake valves, or early ignition timing.

Backing the Air bleed screws out, makes the idle circuit leaner.  Since you have no accel pump for when you open the throttle, a lean idle circuit will make throttle response worse, maybe even dismal, especially from low throttle settings.  You should certainly be able to idle much closer to 1050 RPM.  With correctly balanced carbs and the lowered back pressure from the exhaust, I would expect to require a richer idle circuit setting, not leaner.  (Maybe 3/4 or 7/8 turn?)  After you get the main and throttle valve sorted, you adjust the air bleed for good response to 1/2 throttle travel changes under engine loaded conditions.

But, if your carbs aren't balanced, a cylinder with a slide more open or closed than the others will spit and or pop because that cylinder wants to run and a different speed than the others, but can't since it is tied to a common crankshaft.

This all assumes that the carbs are clean and in good working order from a fuel flow perspective.

Cheers,

[fastbroshi]

I wouldn't expect a 98 main to be large enough, as more oxygen should be available during each cycle. 
I'd probably guess that K model settings (main AND throttle valve) would be more appropriate.  But, I'd sure look at spark plug deposits before I made changes.  (and verify that all cylinders were operating with the same flavor deposits.)

  I thought that the IMS would compensate if I adjusted it out but I guess I got that backwards.  I have 100 and 105s ready to install.  What would you recommend?

As for popping in the exhaust...  Are you sure the exhaust gaskets aren't leaking?

90% sure, as they were brand new and at part throttle I hear no popping.  If they were leaking wouldn't they pop regardless of throttle twist position?

  I'm thinking I should:

1. Pull the plugs and note condition.

2. Recheck exhaust gaskets - with a candle or lighter to see if the flame wavers (dangerous?)

3. Install bigger mains.

4. Try to sync the carbs with the stock IMS setting.

Install bigger idle jets? Is this necessary?  Kinda hard to find, though I think these are it.

   http://www.motorcyclecarbs.com/Keihin_Pilot_Jet_N424-22_C82.cfm

If so, what size would you recommend?

[TwoTired]

  I thought that the IMS would compensate if I adjusted it out but I guess I got that backwards.  I have 100 and 105s ready to install.  What would you recommend?

069A carbs don't actually have an IMS (Idle mixture Screw) they have an Idle air bleed screw.  The later PD carbs have the IMS.
I'd go with #100s (assuming the spark plugs show lean).  I'd also change the Throttle valve jet needles from the #2 position to the #4 position like the K models have.  (assuming you are keeping the no baffle open exhaust, which I wouldn't.)
The alternative is to start with richer mains, do the WOT plug chops and see if they are right for your set up.  If not then go smaller.  But, maybe the #100s are enough?  I just don't have any combustion deposit information to make a solid recommendation.

90% sure, as they were brand new and at part throttle I hear no popping.  If they were leaking wouldn't they pop regardless of throttle twist position?

Usually the popping is more pronounced upon deceleration.

  I'm thinking I should:

1. Pull the plugs and note condition.

Good idea!  Especially if you can do a WOT plug chop!

2. Recheck exhaust gaskets - with a candle or lighter to see if the flame wavers (dangerous?)

I don't have much faith in that approach.  I would use aquarium tubing, about two feet, one end in the ear canal and the other as a probe.  You'll hear exhaust "pips" where it leaks.
I once ruined 4 brand new exhaust seals by allowing the muffler to rest unsupported during assembly.  The top part of the seals all compressed more than the bottom and they would never seal.  I had to replace them and use the proper procedure for exhaust system installation (blocking up the mufflers to near correct final position).

3. Install bigger mains.

 
If you are keeping the no baffle low restriction exhaust, then you likely have no other choice.  But, plug deposit information would be a better guide than a simple guess.

4. Try to sync the carbs with the stock IMS setting.

 
Stunning idea!   
The Idle air screws are the last thing to fine tune.  Set them to stock until it is time to do so.

Install bigger idle jets? Is this necessary?  Kinda hard to find, though I think these are it.

I'd be surprised if this is necessary.  But, the most open exhaust I've used is a MAC system.
I'd worry about the idle system last and get the top and midrange mixtures for the carbs right first.

You need to get the idle down to a more reasonable level so adjustments there can truly dominate without interference from the throttle valve fuel supply, and all the carbs are working at the same level after carb sync.

Cheers,

[fastbroshi]

  Okay, much warmer today as of about 4 pm.  Went for a ride (to go get spark plugs, of course) and much if not all of the bog on idle is gone.   I reset the air bleed screws to one turn out.  Couldn't quite get the idle down to 1050 w/o a little racket.  Turned an 1/8 of a turn in and it smoothed quite a bit, but the tach dances a little still.  But it will go down that low. 
  Just thought I'd mention, I'm running 93 octane fuel with a couple or three tblsp. of Marvel Mystery Oil.
  I'll pull the plugs and take some pics. 
  Very little to no popping observed while on the ride.  While in 2nd gear I was caught behind a vehicle going about 20 mph, not accelerating just holding speed, and to my ear the motor sounded off.  Not quite right.  But keep in mind I'm still new to this bike and I'm a pretty green rider.  Off to the garage.

[fastbroshi]

Pics of the plugs, pre plug chop:

http://s412.photobucket.com/albums/pp204/fastbroshi/Plugs/?action=view&current=IM000297.jpg

I'll see if I can get a better camera.

[ieism]

Sync the carbs first.. You're close. The no2 plug looks kinda ok.

Clean the plugs and recheck them with 100 mains in them. see if it improves running.
How did you check the timing? Static?
What clip did you set the needle ? 2nd from top?
What plugs are you using?

The idle jets are usually not the problem. I run pods and aftermarket exhausts without changing them.

[fastbroshi]

  Checked the timing statically then w/ a light.  Looked great after I adjusted it.  It was heinously out of whack.  Really far advanced.  Clip is the 2nd notch from the top.  Plugs are NGK D7EAs. 
  I think TT agreed w/ you about the idle jets.  I think I'll leave them alone and adjust the needle clip and mains. 
  Unfortunately the fellow that lives right by me has some sync guages and has done this before is going to Luckenbach this weekend and wants me to call him Monday  .  It's just as well, gives me time to change the jets.  I can't wait.

[fastbroshi]

  Pulled the carbs today, installed 100 mains, set the clip on the jet needle to the 4th place from the top and rechecked the floats.  Three of them were off by 2 mm.  I took my time and was very precise this time, I know they're right now. 
  To those of you complaining about this process, get new rubbers on the carb and airbox side.  It's a breeze then.  The part that took me the longest was remembering the right way things should come apart just to get after the needles, as last time I separated the rack for cleaning and it was just different in my mind approaching it this way.  Bad news is I disturbed the semblance of a carb sync that was there.
  Got everything all buttoned back up, making sure my boots were tight and my airbox was together.  Went to fire it up and boy is it off.  It will hold a very rough 1500-1600 RPM idlem, and if I give it a little throttle it will kick up to 4k and stay there.  She doesn't sound very happy at all. 
  I hope it's just the sync making it run so rough.  I'll find out hopefully Monday when an acquaintance can hopefully come over w/ his mercury guages.

[HavocTurbo]

After you did all that to the carbs (re jet/ needle adjust/ etc) you didn't put the original plugs back in did you?

Even if you did, you cleaned them? Sometimes even before carb synch the plugs can effect running in a huge way.

After your first run of synching the carbs you'll see how it sounds harder to do than it actually is.

[fastbroshi]

  No actually I didn't.  Did someone mention that here?  I was going over things in my mind and that did kinda flash in there as a possibility, but the pistons are fighting themselves pretty good.  Oh well, one more thing to check off the list.
 

[fastbroshi]

  I thrashed a little bit this evening and put the 98's back in, left the needle at the 4th position down from the top.  Put everything back together and, lo and behold, the bike holds a good idle.  I think those 100s were just too rich.  I can't explain it any other way.  I don't know how this could be given my missing baffle and foam filter, but it seems to be the case.  I went for a test ride, and the idle could sure use a sync, but above that it seems fine and from over 1/4 to full throttle feels much crisper and powerful. 
  Maybe it was just the needle that needed to be affected, I don't know.  Anyhoo, will sync tomorrow and report back.

[HavocTurbo]

If they are way out of synch.....

The difference should be extremely noticeable!!!

I tried reading everything again and you did check your carb boots for leaking right? I guess the screen is getting to me.

Hope everything works!!!

[fastbroshi]

I tend to ramble a bit but it's just in the name of giving other forum members details, I promise.  I checked just by making sure the boots' clamps were all nice and tight and that they were all as flush as they could be.  They're all brand new by the way, intake to carb and carb to airbox.

[fastbroshi]

  Well after pulling my hair out trying to sync the carbs, I took it to a guy close to me and we had it in about 40 minutes or so.  The burble and hesitating I was getting while rolling on the throttle from a stand still under load is still there, but much less pronounced.  This happens in all gears, especially if I crack it open quick.  It gargles for a bit and then goes.  The bike will hold an idle at 1100 or so, but the tach is still jumpy that far down. 
  It was definitely running VERY rich before the sync, and still is.  I took the plugs out and they were very dark all over.  I haven't double checked my uni filter, so I took that out and washed it, but left some oil in it.  It was a soppy mess, I put too much in last time.
    I think when I last took them off the bowls might have been fine before I reset them.  I'm pretty sure I set them to spec - 22mm. 
   Now if my carbs truly needed bigger mains, would they have been acting like it regardless of the bowls' float height setting?

[HavocTurbo]

I would think, since you are really running rich, that needing bigger mains would not be your problem.... regardless of float height.
I could be way off here but just to reiterate, you have pod filters and an open exhaust yes? Sadly I cannot remember.
My experience with pods and such has led me to try to tune each carb individually and while that takes FOREVER... it works.

For you my suggestion would be to try to check needle height along with maybe some smaller mains given that it's extremely rich at idle.
Again I'm no carb expert, far from it actually, but my problems are usually waaaaay too much gas as I like to fling myself down the road. 

[fastbroshi]

  I am running the stock airbox. Stock exhaust, baffle removed, and a uni filter.  I explained I had some popping in the exhaust that I concluded and others agreed that I might be running slightly lean upon deceleration.  The spark splugs shown in a link above were very close to being tuned well.  But maybe they were just a bit off becuase of a lack of a good carb sync? 
  I noticed as we worked, if it got a bit more out of kilter, the popping would become worse, and eventually went away as the sync got better.  There's no popping anywhere now, but my plugs weren't friggin black before. 
  Needle jet clip is in the 4th position from the top.
  My observations were done on the ride home after we synced it.  Would this time sitting idling and periodically revving have fouled the plugs so much?  I'm thinking I need to go to the 3rd needle jet position.  Not sure if I need to move mains yet.  Oh yeah I almost forgot, I'm getting lousy mileage.

[mlinder]

Your main jets arent doing anything at idle.

Do this:

Get new plugs.

Let the bike idle with the new plugs. Do not open up the throttle.

Use a fan to keep the engine cool.

Pull plugs and look at them.

Rich? Then adjust air screws.
Lean? Adjust airscrews the other way.

Get another set of new plugs.

Get on a long straight away. Open throttle to about 2/3rds, hold it there.
Use the kill switch to kill the engine. Check plugs.

Rich? let the needle down onbe notch (move circlip one up)
Lean, do opposite.

ANOTHER new set of plugs.

Same long straight away.

Hold at WOT for as long as possible.
Use kill switch to kill engine.

Look at plugs.

Rich? Go down one size on main jets
Lean? Go up one size.

Remember to pull in clutch when you hit the kill switch.

Anyway, this will help you determine WHERE your bike is runnign rich.

[TwoTired]

The 550 WILL run rich at idle.  It has to, in order for the throttle response to be usable.  When you open mechanical slides, the carb throat vacuum is significantly changed and little is drawn from the fuel jets until the engine RPMs pick up, carb air speed increases, and venturi effect deepens the vacuum drawn on the fuel jets.

I've tried to describe this before, and few seem to understand.
In gear, near idle RPM, open the throttle about 1/2 of total travel.  There are three possible engine responses.
1. The engine picks up smoothly, indicating correct idle mixture.
2. The engine does a wheeze, almost like the spark quit.  Coming back on the the throttle the engine immediately gets power and behaves "cleanly" as it should for that throttle setting.  This is "Too lean" an idle setting.
3. The engine stumbles, burbles but still fires once in a while. Coming back on the throttle the engine still burbles until the excess fuel clears enough for the engine to run on every spark cycle.  This is "Too rich" an idle setting.

These throttle response symptoms assume the main and throttle valve are set correctly as they do contribute a small amount at idle setting and certainly contribute when the slides are raised and vacuum is present in the carb throats.  The throttle valve does not completely close off the when the slides are at idle.  And, they certainly are allowed to flow when the slides are raised.

Does the engine run better with the air filter removed?
Does the engine run better with a bit choke applied?
Do all the spark plugs show the same pattern of deposits?
Besides "lousy" what exacly is your fuel mileage?

[fastbroshi]

The engine stumbles, burbles but still fires once in a while. Coming back on the throttle the engine still burbles until the excess fuel clears enough for the engine to run on every spark cycle.  This is "Too rich" an idle setting.

  This is exactly what mine is doing.  Even before I synced the carbs.  It's worse now w/ the needle jet clip on the 4 position down. 

Does the engine run better with the air filter removed? Will test and respond later.
Does the engine run better with a bit choke applied?  No, it will almost immediately die.
Do all the spark plugs show the same pattern of deposits? Will test and respond later.
Besides "lousy" what exacly is your fuel mileage? Not sure if I want to ride enough today to test this as it's a bit cold and really windy.  Up until today,  I could top up and the bike would need to be on reserve when fuel got slightly below the rivets for the Honda badge, as seen from the inside of the tank.

[mlinder]

The 550 WILL run rich at idle.  It has to, in order for the throttle response to be usable.  When you open mechanical slides, the carb throat vacuum is significantly changed and little is drawn from the fuel jets until the engine RPMs pick up, carb air speed increases, and venturi effect deepens the vacuum drawn on the fuel jets.

Right, but not so rich that it loads up your plugs to the point that it starts missing.

[mrbreeze]

My bike's a 750 but the carbs on a 550 should act the same way. I think the problem is your needle setting.If your clip is at 4th from top....you are running it in the almost richest position.Mine is at the 2nd from top(almost leanest position). I started out in the middle and went to where you are now(4th from top).It ran worse.I went to 2nd from top and that was the best.After your needles are set,you don't have to pull the carbs anymore(at least on the 750).You can experiment with different mains but I would do the carb synch first.Then when you get the mains where you want em....go back and synch again.
I think you had your needles set right to start with but didn't synch the carbs until you put the needles too rich!!!!

[TwoTired]

The 550 WILL run rich at idle.  It has to, in order for the throttle response to be usable.  When you open mechanical slides, the carb throat vacuum is significantly changed and little is drawn from the fuel jets until the engine RPMs pick up, carb air speed increases, and venturi effect deepens the vacuum drawn on the fuel jets.

Right, but not so rich that it loads up your plugs to the point that it starts missing.

Agreed.

Glad you're feeling better, M.

Cheers,

[mlinder]

The 550 WILL run rich at idle.  It has to, in order for the throttle response to be usable.  When you open mechanical slides, the carb throat vacuum is significantly changed and little is drawn from the fuel jets until the engine RPMs pick up, carb air speed increases, and venturi effect deepens the vacuum drawn on the fuel jets.

Right, but not so rich that it loads up your plugs to the point that it starts missing.

Agreed.

Glad you're feeling better, M.

Cheers,

Sorry, sometimes I assume that people have basic understanding of how aircooled carbed engines without accelerator pumps work :/ . So I assume they already know that idle mixture needs to be on the rich side for throttle response. I need to remember that they wouldn't be asking these questions if they did.

Anyway, thanks, I am feeling better, and I'm glad you are feeling better too, Lloyd.

[fastbroshi]

  I put new plugs in and let it warm up for about 10 minutes in front of a fan.  Checked all 4 plugs, 1 and 4 looked like that chocolate milk color.  Three and two looked clean as a whistle.  Removing the airbox lid and air filter made it run a little better, not very much.  Someone unfamiliar w/ these bikes probably wouldn't have noticed.  So I put my hand in front of the inlet and it started to choke.
  Took it out for a spin, and there the slightest little burble getting moving in 1st.  I got on a good stretch of asphalt and quickly went from 1/8th to 3/4 throttle and it surprised me the difference was so distinct.  So that was good.  Next I tried snapping the throttle open to see if I would get any hesitation.  None.
  Again, my air bleed screws are 1.5 turns out.  When first starting, the choke helped, but the revs soon started dropping. 
  So could it be that I had my sync off long enough that it fouled my plugs to the point I was experiencing the aformentioned symptoms?
  If it's warm enough tomorrow I'll do some plug chops from 1/2 and WOT. What speed and gear would you all recommend?

You can experiment with different mains but I would do the carb synch first.Then when you get the mains where you want em....go back and synch again.
I think you had your needles set right to start with but didn't synch the carbs until you put the needles too rich!!!!

  I'm thinking you may be right.  After the plugs were really close.  Should I be able to get away without a baffle in the exhaust and a foam filter and making no changes in the carbs besides the air bleeds?