Author Topic: 78 550K Carb cleaning help needed  (Read 11462 times)

0 Members and 1 Guest are viewing this topic.

Offline bhkrause

  • Full Member
  • *
  • Posts: 65
Re: 78 550K Carb cleaning help needed
« Reply #25 on: May 05, 2008, 10:52:36 am »
Yuppers.  The trick is to have the valve seated with absolutely minimal pressure on the pin. 
Play with it a bit, you'll get the feel of it pretty quickly.  And I mean that in a strictly carburated way...   ;D

78 cb400TII
77 cb750Finabox
current sohc #346
original sohc #2663
01 zrx1200r

Offline jason teamshralp

  • Enthusiast
  • **
  • Posts: 204
Re: 78 550K Carb cleaning help needed
« Reply #26 on: May 06, 2008, 08:23:23 pm »
pulled my slow jets out today and blasted them with carb cleaner and ran a small wire through it. What difference that made! ;D I was scared to pull them out the previous time i went through the carbs because they were kind of stuck. but now that they are cleaned the first half of throtle is perfect. but now i have an issue WOT. it's like the throttle falls off after about 3/4 throttle.
 ???
any tips? is it main jet? I have pods, and 4-1 exhaust.

Offline BlindJoe

  • Expert
  • ****
  • Posts: 1,184
Re: 78 550K Carb cleaning help needed
« Reply #27 on: May 06, 2008, 08:31:31 pm »
pulled my slow jets out today and blasted them with carb cleaner and ran a small wire through it. What difference that made! ;D I was scared to pull them out the previous time i went through the carbs because they were kind of stuck. but now that they are cleaned the first half of throtle is perfect. but now i have an issue WOT. it's like the throttle falls off after about 3/4 throttle.
 ???
any tips? is it main jet? I have pods, and 4-1 exhaust.

Yep, get some 105 mains and you should be good

Offline jason teamshralp

  • Enthusiast
  • **
  • Posts: 204
Re: 78 550K Carb cleaning help needed
« Reply #28 on: May 06, 2008, 10:42:30 pm »
I heated mine up with a  propane torch until it glowed and the crud cooks out. Use a welding tip cleaner to clear it. I spent about an hour per jet to clean each. Make sure the little emulsion holes on the side are clear. I soaked mine in GM upper cylinder cleaner. I also used sea foam. I also found an easy way to install the carbs.  I used two long wood clamps to draw the carb bank back onto the engine. spray the inside of the rubber tubes with silicone and then put a clamp on each side of the carb rack. the clamp goes between the piece that joins the carbs and the exhaust flange. draw each side in a little at a time. mine went on in one minute.

should I be able to see light coming through the slow jets, the length of the tube and not just the emulsion holes???

Offline BlindJoe

  • Expert
  • ****
  • Posts: 1,184
Re: 78 550K Carb cleaning help needed
« Reply #29 on: May 06, 2008, 10:55:14 pm »
yes, the easiest way to tell if its clear is to turn off all the lights and hold a flashlight in front of it, you should see the light passing through the side and center holes

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: 78 550K Carb cleaning help needed
« Reply #30 on: May 06, 2008, 10:55:24 pm »
should I be able to see light coming through the slow jets, the length of the tube and not just the emulsion holes???

With the jet removed from the carb body, yes.  But, even fluid will block the light.  Blow dry first.

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline jason teamshralp

  • Enthusiast
  • **
  • Posts: 204
Re: 78 550K Carb cleaning help needed
« Reply #31 on: May 06, 2008, 11:24:42 pm »
should I be able to see light coming through the slow jets, the length of the tube and not just the emulsion holes???

With the jet removed from the carb body, yes.  But, even fluid will block the light.  Blow dry first.

Cheers,


Thanks TT, you have helped a lot. I'll clean them some more when i swap out the mains for 105.

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: 78 550K Carb cleaning help needed
« Reply #32 on: May 07, 2008, 12:21:13 am »
The standard main jet for the 78 PD carbs is a #90.  Jumping to #105 is a 16% leap.  Why do you think such a large jet will be required for WOT?  I would expect a 100 or a maybe a 102 to be a better first choice. That's still 10-13%.  If your midrange is still lean then raise the jet needle a notch.  But, then, I'm just speculating.

Cheers,



Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline BlindJoe

  • Expert
  • ****
  • Posts: 1,184
Re: 78 550K Carb cleaning help needed
« Reply #33 on: May 07, 2008, 12:47:52 am »
The standard main jet for the 78 PD carbs is a #90.  Jumping to #105 is a 16% leap.  Why do you think such a large jet will be required for WOT?  I would expect a 100 or a maybe a 102 to be a better first choice. That's still 10-13%.  If your midrange is still lean then raise the jet needle a notch.  But, then, I'm just speculating.

Cheers,





Hey TT,

I suggested it to him having read this thread http://forums.sohc4.net/index.php?topic=22036.0 and specifically this post:"Thanks Mike!

Turns out my local shop didn't have Dynojet 104s in stock, but they had some Keihin 105 take-offs instead.  Probably came off a CB750!  I went with these.  I guess I'd rather be 1 size too rich than burn up my engine, plus I didn't want to wait another week for shipping.

She's just about perfect now.  She idles nice and smooth at 1000 if desired, no flat spots, no pinging on regular gas, pulls like a demon from a stop, pulls very strong right up to redline in any gear.  I even surprised the heck out of myself pulling out into highway traffic a few minutes ago at WOT.  There was definitely too much traffic today to do a top speed run, but she easily pulls up to 90mph and has LOTS of steam left.

Here's my setup for jetting my 1977 CB550K:

77 CB 550 K
26,468 miles
MAC 4-1
Emgo pods oiled with Uni filter oil
PD46C "lean burn" carbs
105 Keihin mains
stock E2349F needles in 2nd position from top (2nd leanest -- stock position!)
42 pilot jets (stock)
Idle Mixture Screws 2.5 turns out
float height ~14mm
67A Throttle valves (stock) [EDIT: added 8/16/07]
NGK D7EA spark plugs w/about 4,000 miles - stock gap.
Dyna S Ignition
Dyna 5 Ohm coils and wires (with non-resistor caps)
Timed statically to stock advance per Dyna S instructions
87 octane gasoline (with up to 10% ethanol warning on pump)
My elevation is about 200 ft. above sea level.

Temps after (slightly fun) run:  Right side bank #4 at base gasket 278F, at head gasket 303F, ambient ~85F.

Thanks to everybody!

Ed "

While there may be some other variables he'll have to account for it should get him in the ballpark, don't you think?

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: 78 550K Carb cleaning help needed
« Reply #34 on: May 07, 2008, 02:02:28 am »
As I said, I'm speculating/extrapolating.

Ed found a setting he is comfortable with.  My gut feeling is that he stopped experimenting at some point less than ideal.  (I've got no problem with this. Ideal jetting is quite time consuming)  Anyway, I base this on his reported fuel mileage.  Stock 77-78 550s get 50MPG or better.  His gets just under 40MPG.
http://forums.sohc4.net/index.php?topic=32596.msg345608#msg345608

This makes me think that he is probably still jetted too rich, since he's had no engine mechanical modifications, only inlet and exhaust changes.
I suppose he could be spending a lot of time in the lower gears.  But, his mileage is 20% worse than a "normal" 77-78 550.  Why is his so inefficient compared to stock, I question?  Could it be over jetted?

To my thinking and based on forum posts, the 105 is too big (for the PD carbs), and the main needle was left at the stock position as a way to compensate for the too large main.  I would expect to raise the needle a notch (as a midrange compensation for the external breathing changes) and then use a smaller main than was chosen.  But, I'm NOT removing my stock air box and pipes on my 78 to prove my speculation!  I like the way it runs now just fine!

These bikes do make the rider feel better when running too rich rather than too lean.  But, I'm not sure the rider can tell the difference between running just right and running a bit too rich.  The exhaust analyzer at the dyno shop can, though.  But, that usually costs money for those finite data points.

Feel free to consider my posts as "noise" to be ignored.  I just like to know why things work.  And, why they don't adhere to ideal theory when reported to the contrary.

Cheers,

Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline BlindJoe

  • Expert
  • ****
  • Posts: 1,184
Re: 78 550K Carb cleaning help needed
« Reply #35 on: May 07, 2008, 02:32:45 am »
Ok, thanks for the clarification.

Offline ugmold

  • Full Member
  • *
  • Posts: 70
Re: 78 550K Carb cleaning help needed
« Reply #36 on: May 07, 2008, 06:30:22 am »
Hi folks,
Finally got back to my carbs. I was able to set all the carbs floats to 12.5mm. All were close except #4, which was way off, I'll keep an eye on it.

I put all my images here, and hope to clean up my "Honda" website soon:

http://www.goomer.com/honda/cb550k.html

New Questions:

1. I found putting the choke plates back on to be a pia, and will save this for last in case I have to pull the carbs apart again.

2. Upon adding #2, I ignored the choke spring/coupling and I know its not right, anybody help here?



3. Carb 1 seems to have an open gas intake, like the connector (aluminum?) tubes with o-rings, am I missing something here? Also above it looks like another connector for the rubber hose? weird.


4. Next to where the gas line connects is another smaller connector, what happens with this?


Thanks so much...terrific thread for me!
ugmold



Offline jason teamshralp

  • Enthusiast
  • **
  • Posts: 204
Re: 78 550K Carb cleaning help needed
« Reply #37 on: May 07, 2008, 03:30:20 pm »
where is a good place to buy some slow jets anyways? I live in Portland, OR so there is probably something around here. Is there a place online?

Offline bhkrause

  • Full Member
  • *
  • Posts: 65
Re: 78 550K Carb cleaning help needed
« Reply #38 on: May 08, 2008, 07:39:04 pm »
Forrest - hate to tell you, but you may have to slightly separate the 2 and 3 carbs.  The linkage that the cable attaches to should be at the back end of the carbs, not the front.  This is probably why the "throttle wheel" is touching the choke linkage.  I remember going through the same thing, vaguely remember using a string somewhere to get the spring set properly...   ???

Edit - never mind, it's positioned right, but for some reason the choke linkage look like it is over too far under the throttle cable wheel.  If you flip the choke linkage piece up and pull it through to the back of the carb and pull it back, do you get clearance between the two pieces?

bk
« Last Edit: May 08, 2008, 07:46:06 pm by bhkrause »
78 cb400TII
77 cb750Finabox
current sohc #346
original sohc #2663
01 zrx1200r

Offline ugmold

  • Full Member
  • *
  • Posts: 70
Re: 78 550K Carb cleaning help needed
« Reply #39 on: May 10, 2008, 02:26:16 pm »
Success!
Thanks BK, TT and  others. I got the choke linkage fixed by looking at another similar thread here:  http://forums.sohc4.net/index.php?topic=30229.0

I put the carbs on the bike and it started on the 10th kick! Sounded pretty good.

However (of course)

Are the carb rubbers that are between the manifold and the carb suppose to sit flush against the 4 carb mounting plate, or is there a gap? I have about 1/3 of an inch gap and couldn't seem to push them on better.

Also #2 has no suction when I put my hand over it, although my hand gets wet from gas, other cylinders feel fine.

I went ultra slow around my block, got it into 2nd. The bike really feels impressive, smooth, quiet. But I was almost at an idle. When you crack the throttle at a standstill it rips, but seems to hesitate at getting back to idle rpm. The throttle was sticky at the carb mech end, a little lube loosened it up, but I think it may be something other than this.

Thanks, will be updating my website and including the other photos I mentioned, including BK's helpful photos and tips. (BTW BK, I re-exaimed the float valve and one spring was sticky...I would have never known they were spring loaded)

Ugmold

Offline BlindJoe

  • Expert
  • ****
  • Posts: 1,184
Re: 78 550K Carb cleaning help needed
« Reply #40 on: May 10, 2008, 02:33:42 pm »
Yes the rubbers should be flush with the carb plate, if the rubbers are hard it can take alot of force to get them on all the way, try wiggling the carb bank up and as you push as hard as you can and they should go in eventually. Putting some Vaseline on the rubber also makes it easier to get them in.

The slow return to idle is indicative of a carb sync being needed, or an air leak somewhere

For the throttle stickiness you could try unscrewing the throttle housing and spraying some wd-40 or the like down the throttle cables.

Offline bhkrause

  • Full Member
  • *
  • Posts: 65
Re: 78 550K Carb cleaning help needed
« Reply #41 on: May 10, 2008, 05:03:24 pm »
Ditto to the carb rubbers.  If they're like the 750, they are not totally interchangable.  They'll fit better on specific spigots, and should fit flush.  Best bet is to fit them loosely, and rotate them around till they look like they're in position. 

Also ditto on the slow return to idle - probably a vacuum leak because they rubbers aren't fitted properly.  Start the bike, spray each rubber with wd40.  If the bike stalls or the idle changes in any way, then the boot that you're spraying has a leak, either at the carbs or possibly cracked.

If your throttle snaps shut, then fixing the vacuum leak will fix the slow return to idle.  If the throttle doesn't snap shut, then you may have some binding somewhere else.

bk

78 cb400TII
77 cb750Finabox
current sohc #346
original sohc #2663
01 zrx1200r

Offline ugmold

  • Full Member
  • *
  • Posts: 70
Re: 78 550K Carb cleaning help needed
« Reply #42 on: May 10, 2008, 07:00:30 pm »
Thanks,

I just came back from the maiden voyage. Drove to a friends house and they were having a party, thanks for calling me...so I left after 2 beers.

It starts on the first kick, but really boggs down around 4k, so quick shifts will get you around on the back roads. Would hear minor mis-fires, mostly when cold, but rev'n it up as well. I'll have to try to push the carbs in tighter, no leverage points to speak of, I guess this could make a big difference in performance. I also didn't hitch up the rubbers to the airbox, I'm sure that will be a joy.

Also 1st gear is mighty high, had to ride the clutch, felt like I was taking off in second gear.

Thanks for the help again, I really do appreciate it. Hopefully this post may help someone else.

ugmold

Offline ugmold

  • Full Member
  • *
  • Posts: 70
Re: 78 550K Carb cleaning help needed
« Reply #43 on: May 13, 2008, 11:40:12 am »
I took the carbs off and mounted the rubber to the carbs 1st. Some teflon grease and a tap with rubber hammer seemed to seat them. Was a little tougher to mount them on the manifold on the bike, but wigglin and cursin got them on. Went for a ride and it performed about the same. It idles like a new bike, but anything above 4k it bogs, the air-roar type of sound.

I have the bottom screws adjusted to 1 1/2 turns out, however they were all 2 1/2 to 3 turns before I took the carbs apart. Maybe I'll try 2 1/2 turns.

Suggestions?

Thanks for reading,
ugmold

Offline bhkrause

  • Full Member
  • *
  • Posts: 65
Re: 78 550K Carb cleaning help needed
« Reply #44 on: May 14, 2008, 09:11:49 pm »
Idle screws only affect the bike to about 3k or so, above that the mains are pretty much on their own.  If it's idling well and runs fine down low, leave them as is.

What do you mean by an air-roar sound?  Does the bike just about stall, or does it just bog down until it slows down? 

Does this bike have o-rings between the manifold and the head?  If it does and they're original, that would be another source for a vacuum leak. 

Can you get it to bog in neutral, then spray some wd40 at the boots between the carb and head while it's bogging?  What happens then? 

bk

78 cb400TII
77 cb750Finabox
current sohc #346
original sohc #2663
01 zrx1200r

Offline ugmold

  • Full Member
  • *
  • Posts: 70
Re: 78 550K Carb cleaning help needed
« Reply #45 on: May 15, 2008, 06:56:09 am »
Thanks Bk,

hmm the sound is I guess the sound of it bogging, after 4k. If you left the throttle say 3/4 open around 4k I would think it would eventually stall. In neutral it revs up usually very nice, sounds pretty impressive, no bog, but not when you are riding it.

There is no o-ring just the rubber connection, which looks good, but I will check with wd-40. It also dawned on me that when I pulled out the main jets, I didn't unscrew the jet from the tube because they were pretty much one and I didn't want to damage them, and they looked decent after I cleaned them up. I guess this might be worth looking at again as well.

Thanks again,
ugmold

kevio

  • Guest
Re: 78 550K Carb cleaning help needed
« Reply #46 on: May 15, 2008, 07:51:53 am »
I don't remember, are you still running the stock airbox?  I had a similar issue with my Ducati Monster after running an open airbox prior to rejetting.

Offline ugmold

  • Full Member
  • *
  • Posts: 70
Re: 78 550K Carb cleaning help needed
« Reply #47 on: May 15, 2008, 08:15:26 am »
Kevio,

At the moment the stock airbox is not connected. I thought of this as a factor, but it is a job to reconnect the rubber to the carbs and airbox housing if I have to pull the carbs off again. I wish it was easier. I would think it would make the bike run a little richer if it was connected.
Thanks,
ugmold

kevio

  • Guest
Re: 78 550K Carb cleaning help needed
« Reply #48 on: May 15, 2008, 08:19:20 am »
Yeah, my Duc was punchier until I hit the midrange.  Then it felt like I shifted into too high a gear.  (Bogged down) 

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: 78 550K Carb cleaning help needed
« Reply #49 on: May 15, 2008, 09:30:43 am »
hmm the sound is I guess the sound of it bogging, after 4k. If you left the throttle say 3/4 open around 4k I would think it would eventually stall. In neutral it revs up usually very nice, sounds pretty impressive, no bog, but not when you are riding it.

There is no o-ring just the rubber connection, which looks good, but I will check with wd-40. It also dawned on me that when I pulled out the main jets, I didn't unscrew the jet from the tube because they were pretty much one and I didn't want to damage them, and they looked decent after I cleaned them up. I guess this might be worth looking at again as well.

Thanks again,
ugmold

Definition:
v. bogged, bogĀ·ging, bogs
v.tr.
To cause to sink in or as if in a bog: We worried that the heavy rain across the prairie would soon bog our car. Don't bog me down in this mass of detail.
v.intr.
To be hindered and slowed.
[end def.]

Is this what you mean?
The engine will slow down when the mixture is not correct for combustion.  Either too lean or too rich may cause the engine to not pick up as requested.

If the engine burbles/stumbles when the throttle is opened and then sputters back to life, this is usually a sign of too rich.
If the engine abruptly drops power, and won't pick up until the throttle is once again reduced, it is probably too lean.

The 78 550K has lean burn carbs.  In order to appease the EPA, the carbs were set for as lean an idle mixture as they could get away with.
When the throttle slides are suddenly opened, the vacuum depth in the carb throat reduces.  It is the vacuum that draws fuel through the carburetor jets.  Therefore, whacking open the throttle makes the mixture lean and the engine reduces power.
The 750 actually added an accelerator pump to the carbs during this era, that actually shoot raw gas into the carb throats when the the throttle is opened.
The 550 didn't get this accelerator pump for some reason.  Apparently they could leave the idle mix just over-rich enough to allow the throttle to open a "reasonable" amount and still get pickup within expectations.
The earlier 550 carbs were all set very rich at idle, and thus, have more tolerable behavior to throttle opening aggressiveness.

As you might guess, the Idle Mixture Screws (IMS) can have a large impact on sudden throttle opening engine response.  Setting them too lean will exacerbate, the "Throttle Whack Wheeze".
These IMS adjustments also have a much more limited effective range than prior model carbs (also to placate the EPA and limit user tempering with emission limits.  Also why the the idle jets are not field replaceable).  So, there is only so much you can do with the screws to improve "Throttle Whack Wheeze".

The air filter restriction has a direct influence on the vacuum level in the carb throat  (remember vacuum is what pulls the fuel through the metering jets?) removing the air filter or changing the type (such as pods) again makes the idle mixture lean, and induces more severe "Throttle Whack Wheeze".

Other considerations, bits of info:
The 550 uses rubber couplers to attach the carbs to the intake manifold.  And, there are orings that seal the join between intake manifold and cylinder head.  These can both leak, particularly if disturbed after a 30 year residence.

So, assuming the carbs are clean, the exhaust still has the same back pressure as when delivered by Honda, the air filter has the same restriction as was delivered by Honda, the IMS screws are not turned in too far, the throttle response from idle setting should induce reliable engine pickup when open by up to one half total throttle travel.  If it does not, then something in that previous sentence needs to be addressed.

Midrange throttle response has similar factors, accept that the mixture is dominated by the slide needles. (The slow system in the carb is still providing some fuel, though).  So, assuming the carbs are clean, the exhaust still has the same back pressure as when delivered by Honda, the air filter has the same restriction as was delivered by Honda, the IMS screws are not turned in too far, AND the slide needles are in the proper adjustment position, the throttle response from midrange setting should induce reliable engine pickup when open by up to one half total throttle travel.  If it does not, then something in that previous sentence needs to be addressed.

The main jet dominates the fuel mixture at throttle setting of 3/4 to WOT.  There shouldn't be much "Throttle Whack Wheeze" there.  But, if the engine isn't making expected power at those settings, then the main jet size needs to be addressed.

Finally, all the fuel metering systems in the carbs have an effect on operation in throttle positions other than where they dominate.  So, changing fuel delivery in any one of these may induce a required change in another.  If your bike is stock and still has all the stock components, then reassemble it to the way it was delivered adjusted by Honda, and it will run pretty darned well.


Cheers,

Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.