Topic: Help with PD46C setup

[Retroben]

Hi everyone,
Working on my 1978 CB550K(4). The bike hasn't run in many years but was stored in clean, dry temperature-controlled conditions, unfortunately with fuel in the tank and bowls. I have done a complete, thorough cleaning, and now reassembling the carbs.

The setup is a PD46C, with a Kerker 4-into-1 exhaust and K&N pods. I found a good stock airbox ($40) that I will install after much advice I've heard and read to lose the pods.

Now what I don't understand is what the PO (unfortunately deceased) was trying to accomplish with jetting and pilot screw settings.

Stock main jets: 90  My bike: 100
Stock slow jets: 42 My bike: 42
Stock jet needle setting: 3rd from top (from what I've read here) My bike: 2nd from top. I changed this to 3rd from top.
Stock float height: 12.5mm  or 14.5, I'm seeing both. My bike: 14.5 mm. I m not sure these float tangs could be bent enough to get 12.5.
Stock pilot screw setting: 1-1/2 turns out My bike: 3 full turns out (all four the same)

The exhaust pipes are very bluish grey, if this means anything.
The plugs were all four sooty, but I don't know when or how this thing ran last, so it doesn't really tell me anything.

I'm not after particularly sporty performance, just smooth operation.

Thanks

[lucky]

   

"Help with PD46C set up"

Some members may not know what you are talking about.
It is carbs on a 1978 CB550 people.

FACTS:
Stock main jets: 90  My bike: 100
Stock slow jets: 42 My bike: 42
Stock jet needle setting: 3rd from top (from what I've read here) My bike: 2nd from top. I changed this to 3rd from top.
Stock float height: 12.5mm  or 14.5, I'm seeing both. My bike: 14.5 mm. I m not sure these float tangs could be bent enough to get 12.5.
Stock pilot screw setting: 1-1/2 turns out My bike: 3 full turns out (all four the same)

LUCKY:   3 turns out on the mixture screw seems extreme.

First Please double check that carb number because in this case it is critical.
Big differences between X46A and PD46C.

Can you please double check?

Different jets.
Different float settings.

[Retroben]

Absolutely PD46C. See "before" pics

http://s1093.photobucket.com/albums/i422/bfranchi/1978%20CB550K/PD46C%20carbs%201978%20CB550K/

Having a hard time mating the pairs back together.

[lucky]

I have no reason to doubt you. I just wanted to make sure. Sometimes people are told something and they do not go check. Thanks for the quick reply.

In the photos it looks like the bottom of carb #2 has one extra hole and I assume that is because it has the accelerator pump feature?

You should expect sporty performance.LOL.lol

FACTS:
Stock main jets: 90  My bike: 100
Stock slow jets: 42 My bike: 42
Stock jet needle setting: 3rd from top (from what I've read here) My bike: 2nd from top. I changed this to 3rd from top.
Stock float height: 12.5mm  or 14.5, I'm seeing both. My bike: 14.5 mm. I m not sure these float tangs could be bent enough to get 12.5.
Stock pilot screw setting: 1-1/2 turns out My bike: 3 full turns out (all four the same)

The fact that the PO had pods and 4 into 1 exhaust the
100 main jets seems appropriate.
Slow jets were #42 stock and if it was running pods It seems it would need larger idle jets but since the slide needle IS adjustable it sort changes things.
Some of those 46C carbs had adjustable needles and some did not.
Some had push in idle jets and some did not. (Do not know on yours),  They look like push in jets,no screwdriver slot.

Since the original non adjustable needle would have been on the 1st groove I assume,
because if it was the 1977 46x carb, I cannot imagine a smooth needle with only the middle groove with a clip. Usually all of the non adjustable needles had one groove at the top of the needle.

So this is what I would do.
You are going to use the stock air box and the 4 into 1 exhausts.

I would use the #100 main jet.
Stick with the #42 idle jet for now.
I would put the needle clip on the 2nd groove down from the top.
That should help with those sooty plugs.
Float height 12.5mm. (stock)
Mixture screw try 3/4 turn.

IF the throttle response from idle is not good ( immediate no stumble), then I would get larger idle jets,
if the mixture screw cannot bring it into good throttle response.


If other members of this form know more please jump in.
Remember 1978 only 46C carbs.

Very few members with 1978 46C carbs have reported about their carbs.
The CB550's have the most different carb styles from the factory.

[TwoTired]

The setup is a PD46C, with a Kerker 4-into-1 exhaust and K&N pods. I found a good stock airbox ($40) that I will install after much advice I've heard and read to lose the pods.

The jetting will change with the stock air box.  Are you prepared to rejet twice?  If not, put the stock air box on first.

Now what I don't understand is what the PO (unfortunately deceased) was trying to accomplish with jetting and pilot screw settings.

Stock main jets: 90  My bike: 100
Stock slow jets: 42 My bike: 42
Stock jet needle setting: 3rd from top (from what I've read here) My bike: 2nd from top. I changed this to 3rd from top.
Stock float height: 12.5mm  or 14.5, I'm seeing both. My bike: 14.5 mm. I m not sure these float tangs could be bent enough to get 12.5.
Stock pilot screw setting: 1-1/2 turns out My bike: 3 full turns out (all four the same)

Your bike has had the double whammy to destroy factory carb tuning.  Exhaust back pressure was reduced, changing engine fuel demands, and the pods have significantly altered the carb throat vacuum as compared to the excellent induction Honda put on the bike.  The carb throat vacuum is what pules fuel up from the bowls.  Less vacuum equates to less fuel being drawn through stock metering orifices.  To restore proper a/f mixtures all the orifices and adjustments have to allow passage of more fuel than the smaller orifices can provide with weak vacuum pressures.

Pods are not a specification, however.  They are a style.  Each manufacture's product creates a different vacuum profile which has no predictable parameters.

You may benefit from his post:
http://forums.sohc4.net/index.php?topic=20869.msg258435#msg258435

The exhaust pipes are very bluish grey, if this means anything.

Stock exhaust were headers were double wall to reduce/prevent bluing.  With single wall headers, you may not be able to avoid head pipe bluing.


Cheers,

[Retroben]

Thanks Lucky and Two Tired.

There are five grooves on my needles, yes.

I now get the jackass award for buying a stock airbox off a 1976 550K at a local boneyard. Looks like the filter element and even the mounting and the space for it are all different from my 1978. Plus the airbox I bought doesn't even have the cover or duct (or "duct and cover" for you combat arms types).

I do not plan on reinstalling the pods, even if I have to go through a little extra time and expense to find and install a stock airbox (or modify the one I bought so it will fit).

And yes, there is a hole for an accelerator pump shaft in carb #2, but no accelerator pump installed! Also, I noticed the bowls on carbs #1 and #2 have little ridges in the channel for the bowl gaskets (helps to hold the bowl gaskets in place during reassembly) and #3 and #4 do not. So looks like there might have been some bowl-swapping here?

[Goldbug]

I am also rejetting my PD46C carbs soon. I have a "custom" exhaust with no muffler (thanks, PO). I bought a muffler, I just need to have it installed. I'll be using the stock air plenum thingy (I forget what Honda calls it) with a K&N cone filter and no box (see my CB500 link in my sig for a similar setup). I'm going to try 110 mains with this setup. It's two full sizes bigger but the CB550 was originally jetted around a very restrictive exhaust system which is now gone.

[TwoTired]

I now get the jackass award for buying a stock airbox off a 1976 550K at a local boneyard. Looks like the filter element and even the mounting and the space for it are all different from my 1978. Plus the airbox I bought doesn't even have the cover or duct (or "duct and cover" for you combat arms types).

I do not plan on reinstalling the pods, even if I have to go through a little extra time and expense to find and install a stock airbox (or modify the one I bought so it will fit).

Laudable goal.  But, the correct parts aren't likely to be easy to find.  The PD carbs were a different length, bore spacing, and different inlet flange size.
The rubber couplers fore and aft were a different length and/or diameter size to compensate.  The rubber bits are no longer available from Honda. (Though, I recall seeing a thread where someone was molding repros.)

Anyway, these parts were only used on the 77-78 K model, if you are looking in a local boneyard.  The plenum box may have been bored or the different spacing, but I haven't measured them side by side.

And yes, there is a hole for an accelerator pump shaft in carb #2, but no accelerator pump installed! Also, I noticed the bowls on carbs #1 and #2 have little ridges in the channel for the bowl gaskets (helps to hold the bowl gaskets in place during reassembly) and #3 and #4 do not. So looks like there might have been some bowl-swapping here?

The PD46 carbs never had an accelerator pump on factory models.  PD50, PD41, PD42 models did, though.  The latter also have larger venturis among other dimension changes.

Cheers,

[Goldbug]

I was able to get repros of the rubber velocity stacks from Paul Gabor for $30. They match the OEM stacks I have. They are longer than the ones for my 1973 CB500.

Paul's email is mybluebike2004@yahoo.com

[Retroben]

Sending these off to a shop. Just want to get them back to stock, which might require replacing bowls #1 and #2...where's the missing accel pump? Fingers crossed.

[brewsky]

Just beginning the same exercise with the 46c's on my 78 550k.).

P0 removed the back end plate of the stock muffller baffles, so the exhaust is slightly modified.
-
Added a uni filter in the stock airbox, upped the mains to 100, raised the needle to 4th notch from top, same 42 slow jet, screw 2 turns out...and the plugs still look lean (avg..not plug chops yet)  (D7's)....14.5mm float height

I also noticed the lack of dimples to hold the bowl gaskets in the grooves of the #3 and #4 bowls ......maybe it's a "feature "

[lucky]

Sending these off to a shop. Just want to get them back to stock, which might require replacing bowls #1 and #2...where's the missing accel pump? Fingers crossed.

That is a bad plan. Want to waste lots of $$$$ and get nowhere?
There may never have been a accelerator pump on that carb
It is just that the casting on #2 carb had a provision for a accelerator pump.
If you had posted a photo of the front and back of the carb I would not have mentioned it. Some F model DID have the pump.

Most motorcycle shops will know nothing about those carbs and many of the young guys are afraid of carbs. Believe it or not.

This forum will be your best source of information.

I have been working on Japanese motorcycles for over 40 years.My first job was in a Honda dealership.

[Retroben]

Lucky, the fellow I'm sending them off to has about the same history as you. He and his partner, both Honda mechanics since the 1970s, have a great inventory of spare parts for these and other Keihin carbs. He's charging me a ridiculous small price to re-clean the carbs (if necessary - I didn't remove the pressed-in slow jets), replace my mains, remove, clean and inspect the pressed-in slow jets, reset the float height, assemble and bench synch the set. I trust the guy, he's a respected fellow member of another forum (the CX500 forum).

Honestly, the thing that finally made me give up was the throttle shaft with the spiral spring. No pics or instructions anywhere on how to manipulate the actuator when re-joining the two halves of the set. The choke linkage seems to interfere. I guess I should have shot video when I took it apart, then I could just run it backwards for reassembly   

At least in the meantime I have not destroyed the small choke spring or stripped any threads anywhere, or otherwise harmed the carbs. I want to quit while I'm ahead. I've learned a lot on this bike, now it's time to let some pros help me finish getting it on the road.

[lucky]

Lucky, the fellow I'm sending them off to has about the same history as you. He and his partner, both Honda mechanics since the 1970s, have a great inventory of spare parts for these and other Keihin carbs. He's charging me a ridiculous small price to re-clean the carbs (if necessary - I didn't remove the pressed-in slow jets), replace my mains, remove, clean and inspect the pressed-in slow jets, reset the float height, assemble and bench synch the set. I trust the guy, he's a respected fellow member of another forum (the CX500 forum).

Honestly, the thing that finally made me give up was the throttle shaft with the spiral spring. No pics or instructions anywhere on how to manipulate the actuator when re-joining the two halves of the set. The choke linkage seems to interfere. I guess I should have shot video when I took it apart, then I could just run it backwards for reassembly   

At least in the meantime I have not destroyed the small choke spring or stripped any threads anywhere, or otherwise harmed the carbs. I want to quit while I'm ahead. I've learned a lot on this bike, now it's time to let some pros help me finish getting it on the road.

Seems like you made very smart choices about the people you are choosing to help you.

[Retroben]

I'm not sending these off. I'm going to be patient and finish what I started. I want to learn to do this.
I was afraid of the pressed-in slow jets. I wrapped one in 1200 grit wet/dry sandpaper, grabbed around the sandpaper with a pair of parallel-jaw pliers, squeezed and pulled, the jet popped out without damage. Emulsion holes clean. I'm going to replace them anyway just because I want to.

As a baseline starting point, I'm going to install stock #90 jets, replace the current #42 stock jets with new ones (just in case), set the float height to 12.5, and have the needle on the third (middle 3/5) groove, and pilot screws 1-1/2 turns out. That seems all stock, although I still can't verify the needle setting - don't yet have the K4 addendum to the FSM.

Already test fitted the airbox I got off a '76 CB550K2. The body does fit in the space next to the battery box. Once I get the carb pairs back together I can figure out if the connectors line up, but they sure look like they're pointing straight at the carb insulators mounted on the cylinder intakes. We'll see. I'd hate to go back to the pods but the stock 1978 CB550K4 airboxes are not plentiful or cheap! The element numbers are different between '76 and '78, so I'm not yet sure where I stand on this one.

I think I figured out how to get the pairs back together. With the throttle shaft installed in #3 and #4, I think I need to release the actuator set screw (I had installed the actuator already following instructions for the PD46A, which has the tension-type return spring  - mine has the torsion type that's wrapped around the throttle shaft itself).

Sure wish there was a video.

[lucky]

I'm not sending these off. I'm going to be patient and finish what I started. I want to learn to do this.
I was afraid of the pressed-in slow jets. I wrapped one in 1200 grit wet/dry sandpaper, grabbed around the sandpaper with a pair of parallel-jaw pliers, squeezed and pulled, the jet popped out without damage. Emulsion holes clean. I'm going to replace them anyway just because I want to.

As a baseline starting point, I'm going to install stock #90 jets, replace the current #42 stock jets with new ones (just in case), set the float height to 12.5, and have the needle on the third (middle 3/5) groove, and pilot screws 1-1/2 turns out. That seems all stock, although I still can't verify the needle setting - don't yet have the K4 addendum to the FSM.

Already test fitted the airbox I got off a '76 CB550K2. The body does fit in the space next to the battery box. Once I get the carb pairs back together I can figure out if the connectors line up, but they sure look like they're pointing straight at the carb insulators mounted on the cylinder intakes. We'll see. I'd hate to go back to the pods but the stock 1978 CB550K4 airboxes are not plentiful or cheap! The element numbers are different between '76 and '78, so I'm not yet sure where I stand on this one.

I think I figured out how to get the pairs back together. With the throttle shaft installed in #3 and #4, I think I need to release the actuator set screw (I had installed the actuator already following instructions for the PD46A, which has the tension-type return spring  - mine has the torsion type that's wrapped around the throttle shaft itself).

Sure wish there was a video.

So glad you decided to stick with your project. You were right at the point you are about to learn something and now YOU can make your own video.
Now you are believing in your self.

[TwoTired]

I'm not sending these off. I'm going to be patient and finish what I started. I want to learn to do this.
I was afraid of the pressed-in slow jets. I wrapped one in 1200 grit wet/dry sandpaper, grabbed around the sandpaper with a pair of parallel-jaw pliers, squeezed and pulled, the jet popped out without damage. Emulsion holes clean. I'm going to replace them anyway just because I want to.

I don't know where you got the replacement jets.  But, if determined to replace, then measure the holes on the replacement to see if it is the same as the originals.  Hole size makes a difference, and will particularly effect the idle mixture screw setting. 

As a baseline starting point, I'm going to install stock #90 jets, replace the current #42 stock jets with new ones (just in case), set the float height to 12.5, and have the needle on the third (middle 3/5) groove, and pilot screws 1-1/2 turns out. That seems all stock, although I still can't verify the needle setting - don't yet have the K4 addendum to the FSM.

There is no K4 addendum that I have ever seen or heard off.  Only the K3.

With Kerker, the main will certainly be too lean.  There is some risk of overheating and possibly detonation.  (Are you using ethanol fuel?  That will make it worse)   Do your mixture testing very quickly, or start with #95 mains and the needles clipped in the 4th groove from top.  Start with pilot screws set to 2-3 turns out.  You set these to just rich enough to eliminate stumble with up to 1/2 throttle twist under load, from idle RPM.

Already test fitted the airbox I got off a '76 CB550K2. The body does fit in the space next to the battery box. Once I get the carb pairs back together I can figure out if the connectors line up, but they sure look like they're pointing straight at the carb insulators mounted on the cylinder intakes. We'll see.

You *could* measure the bore centers of the carbs and then do the same with the plenum chamber.

I'd hate to go back to the pods but the stock 1978 CB550K4 airboxes are not plentiful or cheap! The element numbers are different between '76 and '78, so I'm not yet sure where I stand on this one.

Since you are going to do rejet tuning anyway, fit a Uni Nu-4055, in there from the get go.  And then, tune the carbs to the induction and exhaust you are determined to use.

Only "K4" specs I've ever seen ...attached.

[Retroben]

Thanks TwoTired. I'm getting the jets from Sirius Consolidated in Canada. 2-day delivery on everything so far, and they sell the right stuff.

I already ordered the Honda air filter element for $26. Now that I know the Uni filter number, maybe next time. Should I worry that there's no cover on the airbox? Should I try to fabricate one if I can't find one? Is the Uni designed to operate without the airbox cover?

Again, any advice about the order of reassembly for the carbs? I have two sets of two each nice clean carbs. It's the sequence for getting the throttle shaft back in that I'm guessing on, and I don't want to screw anything up.

Thanks
Ben

[TwoTired]

Thanks TwoTired. I'm getting the jets from Sirius Consolidated in Canada. 2-day delivery on everything so far, and they sell the right stuff.

Nice you trust them.  I'll just mention other post threads where non Honda internal carb parts, didn't work out correctly and some have noticed differences in dimensions of aftermarket parts.

I already ordered the Honda air filter element for $26. Now that I know the Uni filter number, maybe next time. Should I worry that there's no cover on the airbox? Should I try to fabricate one if I can't find one? Is the Uni designed to operate without the airbox cover?

The uni is a foam replacement module for direct substitution of the stock filter element.  It has slightly less "restriction" than stock, and tends to lean mixtures a tad, as it presents less pressure drop across the membrane (if not over oiled).  You'll need the leaf spring for both.

The filter doesn't care about the airbox cover.  But, the cover does effect carb jetting to a degree.  Depends on how many times you want to go through the jetting procedure.  Every change you make in configuration has an effect, and requires an adjustment in the carbs, which are too dumb to adapt automatically.

Again, any advice about the order of reassembly for the carbs? I have two sets of two each nice clean carbs. It's the sequence for getting the throttle shaft back in that I'm guessing on, and I don't want to screw anything up.

I've never found the need to dismantle the bank.  If you need pics of the assembly, I have a spare set.  It's not useable but should correctly show assembly orientation.

Here's one with choke linkage I've posted before for another.

[Retroben]

Thanks for the help!

I do have the leaf spring fortunately. I'm going to have to use a zip tie to secure the top rear of the airbox, where I'm missing a bracket. Hey, plastic to plastic, perfect materials mating, and under the seat where nobody should care.

I finally got the carb bank back together. I separated the carbs for several reasons: 1) I have a tiny ultrasonic cleaner that only fits one carb at a time; and 2) there was aerosol white grease sprayed heavily on the linkages, and it was in all the nooks and crannies on the adjacent carb bodies; 3) I wanted to check the condition of the fuel rail o-rings and replace the vent tubes between the carbs.

New (for me) wisdom: If it doesn't feel like it's going together right, it's probably not. Remember, this is a Honda.

[Retroben]

Airbox update: $40 spent for the airbox off the '76 was not entirely wasted. Of course the plenum does not fit.  Found a plenum for a 1978 on ebay $56 incl. shipping, but no boots. Ordered boots from http://www.classicmotorcyclesolution.com/ for another $35 shipped. Honda air filter element $31 from FLIBS. So total cost so far of restoring air intake to stock: $162. Ouch.

[Goldbug]

Bummer. But you'll be rewarded with a good running bike which is somewhat priceless.

[Retroben]

Finally got all my parts and started the bike today. As expected, big leaks out of the header pipes (new crush gaskets on order), but she started immediately and sounded smooth.

Until I hit the kill switch because there was fuel pouring out of all four carb overflows.

On advice from members here, I changed the float height from 14.5 to 12.5. Float needles are brand new from a reputable supplier, the seats are clean, and I do think I have the floats in right side up. So if I change back to 14.5, should that fix it?

[TwoTired]

Did you put the floats in flat side toward earth?

Side stand parked or center stand?

Tapping on the bowls didn't help?

New seats and metal needles need some time to "marry" and seal together, (unless you lapped them in during installation).  Some run vibration (wear) may be necessary to make them get a reliable seal.

My 78 Cb550K  PD46c carbs had the floats at 14.5mm when I opened them up.  I left them at that setting as it worked well that way before, and surprise, it worked well after the cleaning and reassembly.

I have no explanation why the Honda set up guide states 12.5mm, except to guess it was an attempt the richen up the entire operating range as it ought to do with a higher fuel level.

Cheers,

[Retroben]

Did you put the floats in flat side toward earth?

Side stand parked or center stand?

Tapping on the bowls didn't help?

New seats and metal needles need some time to "marry" and seal together, (unless you lapped them in during installation).  Some run vibration (wear) may be necessary to make them get a reliable seal.

My 78 Cb550K  PD46c carbs had the floats at 14.5mm when I opened them up.  I left them at that setting as it worked well that way before, and surprise, it worked well after the cleaning and reassembly.

I have no explanation why the Honda set up guide states 12.5mm, except to guess it was an attempt the richen up the entire operating range as it ought to do with a higher fuel level.

Cheers,

Thanks, TwoTired.
Yep, flat side toward earth. 
Center stand, tank mounted on stepladder next to the bike, about a foot higher than the installed position.
Tapping on the bowls - All four? Would all four floats hang up at once? They all seem nice and free.
I didn't lap in the new float needles. But this is a flood, not a trickle. And my float needle seats look nice and clean and smooth.
My floats were set at 14.5 when I opened the carbs up, but I have no idea how or even when this bike ran last. I'm changing back to 14.5 - seems to me like a sensible first step. I just hate taking these carbs off and on - and I worry that the insulators are going to give up on me from too much in and out. And I don't know how to set float height with the carbs on the bike.
I'm not going to start the bike again until I get the exhaust gaskets installed anyway.