Topic: Carb Wizards... I need your sacred wisdom

[Adam_F]

So I started asking about this shortly after I completed my recent top end rebuild.  You can check out that thread here if you're interested:

http://forums.sohc4.net/index.php?topic=137543.0

Immediately after the rebuild, the bike was running better than ever.  I didn't touch the carbs (069A), just reinstalled them.  A couple weeks later, I started having trouble at idle.  Bike ran GREAT, but it would die at idle unless I turned the idle screw up to 3k or stayed on the throttle.  So I decided to go into the carbs and clean them, check floats, etc.

The internals were mostly really clean, with the exception of the emulsion tubes.  I didn't remove the carbs from the rack, nor did I soak them.  I simply removed and cleaned all jets and passageways.  I also double checked the float heights and fuel lines.  Everything was set to stock specs for the 069A carbs.  After I reinstalled them, things were much better. 

The bike no longer dies at idle, but it is still having idling issues.  I would describe the idle as "occasionally or subtly erratic."  Basically, it will be purring away at about 1200 most of the time.  After longer rides when the bike is nice and warm, or a lot of stop and go riding... the idle will become more erratic and occasionally drop a few hundred rpms.  When it does this, it sounds really clanky, like the bike is going to die.  But since I cleaned everything, it never actually does.  The idle never raises, and it never hangs.  So here is what I've done to see if I can find the problem:

Readjusted valves and cam chain tension
New Air filter (uni foam, fits in stock box)
Vacuum Synch - Helped with overall engine noise, but didn't fix erratic idle
Check for air/vacuum leaks - Sprayed WD40 and didn't find anything (though Im still believe this could be the root of my problem)
Air Screw Adjustments - I originally had them set to 1 and 1/2 out.  Started leaning it out a bit more to see if that helped... no difference.  But speaking of air screws, are there supposed to be orings here?



After leaning out the bike a bit, I was having symptoms of running rich (bike running worse when hot and stumble off idle), so I pulled the plugs.  Here they are in order from left to right (1-4):



The plugs look lean as expected except for #1.  Looks like I need to check the float again on number one.  Smelled like gas as well    I readjusted the airscrews back to 1 and 1/2 and will plan to check them again tonight.

I've done some research on here for folks with similar idling issues and it turned out to be their coils.  From the look of things, my coils look relatively new.  I never experience any dropping of cylinders when riding, so I'm guessing that's not the problem (though I still need to look into them deeper).  As I mentioned above, the bike runs GREAT through all the gears!  I do get relatively poor fuel economy (around 30 mpgs unless I'm on the highway, its a bit better).  I'm sort of a perfectionist and the bike is very ride-able... But I won't rest until it idles smooth and steady once again 

Any help or suggestions would be greatly appreciated!

 

[Deltarider]

The internals were mostly really clean, with the exception of the emulsion tubes.  I didn't remove the carbs from the rack, nor did I soak them.  I simply removed and cleaned all jets and passageways.  I also double checked the float heights and fuel lines.  Everything was set to stock specs for the 069A carbs.  After I reinstalled them, things were much better.

Wise of you. This is all what it takes.
BTW airscrews on these oldstyle model carbs don't have O-rings, The later PD carbs on the 500/550K3 do.
Did you just check the float height or were you tempted to 'adjust'?

I'd start with the ignition. Is #1 sparking where it should or is spark maybe lost elsewhere?
How is #1 spark plug cap? Could be a rotten spark plug.
How is the ignition timing and advancer?
I wouldn't suspect the coil.
Is slow jet #1 carb still in it's place or did it drop in the bowl (I had this once). Does the O-ring around the #1 main jet still seal well?

[Adam_F]

The internals were mostly really clean, with the exception of the emulsion tubes.  I didn't remove the carbs from the rack, nor did I soak them.  I simply removed and cleaned all jets and passageways.  I also double checked the float heights and fuel lines.  Everything was set to stock specs for the 069A carbs.  After I reinstalled them, things were much better.

Wise of you. This is all what it takes.
BTW airscrews on these oldstyle model carbs don't have O-rings, The later PD carbs on the 500/550K3 do.
Did you just check the float height or were you tempted to 'adjust'?

I'd start with the ignition. Is #1 sparking where it should or is spark maybe lost elsewhere?
How is #1 spark plug cap? Could be a rotten spark plug.
How is the ignition timing and advancer?
I wouldn't suspect the coil.
Is slow jet #1 carb still in it's place or did it drop in the bowl (I had this once). Does the O-ring around the #1 main jet still seal well?

Thanks for the response.  One thing I forgot to mention... I have a Dyna S ignition, so no points/timing.  The plug caps looks brand new (like whoever had the bike before me replaced them).  The slow jets in my carbs screw in (unless I have the jet confused), so its very doubtful that it fell out.  I did have to adjust the float height on carb 4 because it was off quite a bit.  But I was careful and triple checked everything.  Really scratching my head on this one....

[dave500]

check all the jet numbers are the same for all four carbs and that the slide needle clip is in the same position for all carbs.

[Adam_F]

check all the jet numbers are the same for all four carbs and that the slide needle clip is in the same position for all carbs.

Thanks Dave.  Definitely checked that and made sure everything was set to stock.  After my rebuild the bike ran great for a couple weeks (much thanks to you), and I never had any similar issues before removing the carbs.  Either way, it was good to clean them and learn my way around the internals.

[dave500]

check over your ignition again,check the plug caps resistance.

[TwoTired]

Your idle issues could easily be caused by that blackened sooty spark plug shunting spark at random.

Replace them or move it to another cylinder that can clean that soot off with a good run.

I would do this before mucking with anything else, or you can compound the problem with other changes.  If #1 repeatedly soots up, then fix the carb issue related to it; float height, dropped jet, emulsion tube, etc.

You simply can't fine tune carbs or ignition issues with dirty fouled plugs.

Do you have the stock muffler/exhaust matched for the 069A?

Also, it's better to state what you believe stock setting are.  That way, if there's a wrong assumption, we can catch that.

[BobbyR]

Dynas have been known to start acting up when warm. It happened to me and the idle gets clanky.

[Adam_F]

Dynas have been known to start acting up when warm. It happened to me and the idle gets clanky.

Oh yeah?  Did you end up replacing it?

[Adam_F]

Your idle issues could easily be caused by that blackened sooty spark plug shunting spark at random.

Replace them or move it to another cylinder that can clean that soot off with a good run.

I would do this before mucking with anything else, or you can compound the problem with other changes.  If #1 repeatedly soots up, then fix the carb issue related to it; float height, dropped jet, emulsion tube, etc.

You simply can't fine tune carbs or ignition issues with dirty fouled plugs.

Do you have the stock muffler/exhaust matched for the 069A?

Also, it's better to state what you believe stock setting are.  That way, if there's a wrong assumption, we can catch that.

Thanks TT.  I don't know stock setting off hand, but I get them off a chart you posted a while back.  I do have the original/stock muffler.  It has a couple small holes, but is in decent condition. 

[BobbyR]

Dynas have been known to start acting up when warm. It happened to me and the idle gets clanky.

Oh yeah?  Did you end up replacing it?

Yes I did. It got worse over time. I replaced it with a PAMCO. So far so good. You can also go back to points.

[Adam_F]

Dynas have been known to start acting up when warm. It happened to me and the idle gets clanky.

Oh yeah?  Did you end up replacing it?

Yes I did. It got worse over time. I replaced it with a PAMCO. So far so good. You can also go back to points.

Thanks!  Final ? for ya.  How did you ultimately diagnose that it was your dyna?

[BobbyR]

Dynas have been known to start acting up when warm. It happened to me and the idle gets clanky.

Oh yeah?  Did you end up replacing it?

Yes I did. It got worse over time. I replaced it with a PAMCO. So far so good. You can also go back to points.

Thanks!  Final ? for ya.  How did you ultimately diagnose that it was your dyna?

I was having an intermittent loss of power. Momentary at first and seemingly random. Climbing up a steep narrow mountain road I wound up on two cylinders. 20 mph at 7K steep.  Sat down shot the #$%* with some bikers for an hour and just coasted down to the bottom. She started and I got 1 mile from home when the idle went bad. I reached down and pulled off #3 wire and nothing changed.

Got home checked the coils, ignition wires and wires coming out of the Dyna. Rode the next day and when she got hot, dropped two. Put the points back in, and ran it for 3 hrs.

That may not be your problem, but keep it in mind for the future.

[goldarrow]

Dynas have been known to start acting up when warm. It happened to me and the idle gets clanky.

Oh yeah?  Did you end up replacing it?

Yes I did. It got worse over time. I replaced it with a PAMCO. So far so good. You can also go back to points.

Thanks!  Final ? for ya.  How did you ultimately diagnose that it was your dyna?

I was having an intermittent loss of power. Momentary at first and seemingly random. Climbing up a steep narrow mountain road I wound up on two cylinders. 20 mph at 7K steep.  Sat down shot the #$%* with some bikers for an hour and just coasted down to the bottom. She started and I got 1 mile from home when the idle went bad. I reached down and pulled off #3 wire and nothing changed.

Got home checked the coils, ignition wires and wires coming out of the Dyna. Rode the next day and when she got hot, dropped two. Put the points back in, and ran it for 3 hrs.

That may not be your problem, but keep it in mind for the future.

I had same issues same symptom 2 and 3 went bad

[Deltarider]

Your idle issues could easily be caused by that blackened sooty spark plug shunting spark at random.

Replace them or move it to another cylinder that can clean that soot off with a good run.

I would do this before mucking with anything else, or you can compound the problem with other changes.  If #1 repeatedly soots up, then fix the carb issue related to it; float height, dropped jet, emulsion tube, etc.

You simply can't fine tune carbs or ignition issues with dirty fouled plugs.

Start with what TT suggests.
I once had a slow jet dropped in the bowl, simply because I hadn't fastened it enough. Ofcourse you are careful not to fasten it too much.

[Adam_F]

Dynas have been known to start acting up when warm. It happened to me and the idle gets clanky.

Oh yeah?  Did you end up replacing it?

Yes I did. It got worse over time. I replaced it with a PAMCO. So far so good. You can also go back to points.

Thanks!  Final ? for ya.  How did you ultimately diagnose that it was your dyna?

I was having an intermittent loss of power. Momentary at first and seemingly random. Climbing up a steep narrow mountain road I wound up on two cylinders. 20 mph at 7K steep.  Sat down shot the #$%* with some bikers for an hour and just coasted down to the bottom. She started and I got 1 mile from home when the idle went bad. I reached down and pulled off #3 wire and nothing changed.

Got home checked the coils, ignition wires and wires coming out of the Dyna. Rode the next day and when she got hot, dropped two. Put the points back in, and ran it for 3 hrs.

That may not be your problem, but keep it in mind for the future.

I had same issues same symptom 2 and 3 went bad

Thanks to you both!  As of now, my problems only surface at idle... which leads me to believe its carb related...  After I cleaned all the carbs the bike ran really really well for the first few runs.  I switched around the plugs and number 1 is still black and sooty.  So I'm going to remove them again and dive back into number one.  Maybe something came loose or was plugged up in there.  Last night after riding a bit to test the plugs, the bike was barely holding its idle at all (conditions worsening).  I'm leaving for a week long camping trip tomorrow, but will plan on diving into them next week.  I'll take some pics and keep ya all posted.  Thanks so much for the suggestions.

A

[Adam_F]

A little update.  I just got back from a backpacking trip and came down with strep  ....  Started feeling better today so I figured I'd come back to my bike and try to get to the bottom of my recent issue(s).

As I mentioned in previous posts, I was having trouble holding idle.  I then took the carbs off for a cleaning.  Seemed to help a lot and I thought I was good to go.  But the issue slowly returned.  I pulled the plugs and all of them looked great (toasty brown) with the exception of cylinder 1 (black, but not terribly sooty... though it did smell like gas). 

It had been suggested here that I take another look into carb 1 to see if any of the jets had dropped.  So I took the carbs off again today and everything in number 1 looked great.  No sign that I could see of anything that would cause that cylinder to run richer than the others.  I reinstalled the carbs and went for a ride the afternoon.  As soon as I fired up the bike I noticed that it sounded off.  The exhaust note was lower and more "grumbly" than normal.  After the warm up period I was getting major stumble off idle and a serious grumble sound.  When I got home and felt the pipes (spit on finger test), number 1 was warm, but not sizzling hot like the other three.  The plus side is that it seemed to idle okay (thought I wasn't doing too much stop and go or waiting at lights).

So, my only conclusion at this point is that there isn't enough (or any?) spark on cylinder 1.  I've tried swapping out plugs, and the issue still remains w #1.  Could this be an electrical issue!?  Problem with a coil or spark plug cap?

Any suggestions are greatly appreciated.

Thanks!

A

[TwoTired]

Unlikely spark or #4 would be affected, too.

Anyway, spark doesn't control how much fuel get to cylinder 1.

Did you..
... vacuum sync the carbs at idle?

...clean the emulsion tubes?

...mess with the float height?

..try new spark plugs?

[Adam_F]

Unlikely spark or #4 would be affected, too.

Anyway, spark doesn't control how much fuel get to cylinder 1.

Did you..
... vacuum sync the carbs at idle?

...clean the emulsion tubes?

...mess with the float height?

..try new spark plugs?

Thanks TT.  I did all of those things, with the exception of messing with the float height as it sat 22mm just at the point before it compressed the spring.  Swapped around plugs and still had the issue with cylinder #1.  I understand that the spark isn't controlling the amount of fuel entering the cylinder, but it does serve to ignite it correct?  So if it wasn't sparking properly, that could account for the smell of fuel on the plug.  I'm gonna look into the spark plug caps/connections/etc.  Totally open to other ideas too!

[goldarrow]

Check condition of the plug wire.  On my bike, core wire broke internally so I cut off that section, reconnect with ngk plug wire splicer, and that fixed intermittent firing issues. 

[Adam_F]

Check condition of the plug wire.  On my bike, core wire broke internally so I cut off that section, reconnect with ngk plug wire splicer, and that fixed intermittent firing issues.

Thanks GA.  How could you tell that the core wire had broken internally?  Probably an obvious answer, but I'm picturing x ray vision 

[trueblue]

An ohm meter will tell you if you have a broken wire

Another thing to check is that the tang on the float doesn't have a little dimple where the fuel needle sits on it.  It can cause it to catch randomly and flood one cylinder.  Normally a gentle tap on the float bowl will free it up.  If it has a dimple a little fine sandpaper will cure the problem, just blend the divit into the rest of the float tang .

[lucky]

Did you remove the idle jets and look through them as you held them up to the light?

[Adam_F]

Did you remove the idle jets and look through them as you held them up to the light?

Sure did.  I also carefully ran a high e guitar string through all the tiny holes to make sure they were not blocked.  All of the jets from each carb are stock and appear original.  Float heights are all properly set at the point just before they compress the spring/needle. 

Somehow either too much fuel is still getting in, or there's just not enough spark to ignite it.  I just ordered new spark plug caps and plan on trimming the wires back 1/4 inch.  If that doesn't make a difference, I can test the ohm of the coils and potentially replace them.  If THAT still doesn't work... then.... well, no idea

Thanks for the suggestions though!

[billingstitan]

Man - I am no carb wizard for sure - but I just went through almost the exact same thing on my CB550 - #1 was running cool; plug would get wet and black; would sputter and spit until higher revs.

Thought for sure it was ignition or coils or something as I had just gone through the carbs. Checked plug wires, got new caps, etc. etc etc.

What it finally ended up fixing it was raising the needles by one notch. I thought they were in stock - and technically they were - only 77 CB550 came w both 42 and 38 slow jets, and mine happened to have 42 slows, which meant that stock was actually not center notch, but 2nd from the top.

Anyway - point being - I don't know why #1 really seemed to be the only cylinder affected when all the needles were out, but just throwing that experience at you in case it gives you any clues.

Like you, I cleaned by GD slow jet on #1 about a million times, checked my floats, float valves - changed the points, checked the coils, etc. etc. etc. and was about to pull my hair out - then just tried the needles for a WTF sort of thing - and presto - bike fired on all four and has run perfect ever since.