Topic: Keihin PC 46A stock needle setting?

[cmyoch]

So far, everything I've read on slide needle settings state that the factory settings are dead center. When cleaning my carbs, I noticed that the needles are set to the second position from the top. I do not know the history of this bike but it still had the original exhaust and stock air box. I don't know if this was set from the factory or what any PO may have done in the past. The bike barely ran when my brother bought it but that was due to gummed up carbs.

Any thoughts?

[lucky]

So far, everything I've read on slide needle settings state that the factory settings are dead center. When cleaning my carbs, I noticed that the needles are set to the second position from the top. I do not know the history of this bike but it still had the original exhaust and stock air box. I don't know if this was set from the factory or what any PO may have done in the past. The bike barely ran when my brother bought it but that was due to gummed up carbs.

Any thoughts?

Something is wrong with your information.
What year is the motorcycle?

IS it a CB550 or CB750?
78   CB550K  had    PD46C  carbs. Those had non adjustable needles.
No PC46A's.

Have you actually seen the needles?
If they(slide needles) are adjustable with 5 grooves, then it could b a late 1977 CB550
 

[cmyoch]

Sorry, it's a 1977 cb550. I removed the needles for cleaning last night.

[lucky]

Sorry double post.

[lucky]

Sorry, it's a 1977 cb550. I removed the needles for cleaning last night.

There were two main differences between the 77 and 78 CB550.
The 1977 was
77 CB550K X46A   14.5 float height 90 main jet 38 idle jet    3 needle position
The 1978 was
78   CB550K   PD46C  12.5 float height   90 main   42 idle   NA(not adjustable)


Look at the numbers again. What are they,do you think?
Use a magnifying glass if needed.

[cmyoch]

I went ahead and took photos. Is this the stock needle position in your opinion?

[cmyoch]

...a shot of the clip position.

[lucky]

...a shot of the clip position.

No that needle clip position would not be right.
Since you have an adjustable needle it would be the 1977 version. 3rd groove down.
What size is your idle jet?
Do your carbs have the accelerator pump on carb #2?

Could you look on the ID plate of the frame headstock, Left and right side and see what it says as far as the year?

[TwoTired]

Do note that the carb spec apply to stock configured bikes.  The ones with the stock exhaust and induction.  If either of those have changed the stock carb specs won't be appropriate.

Below is the from the Honda service booklet.

[Deltarider]

Is there a stamped on number on the needle?
The Honda Shop Manual for the 500/550 mentions on p.178: needle E2349F for the CB550K3 and 3rd groove. It doesn't say the carb. number however. I don't know this is of any help because that same page denotes a Date of Issue: July 20, 1977.
Usually not many people ever changed needle positions and float heights. They left them alone, as they were always right. Main jets were changed more often when airfilters or exhausts were non stock. Members of this forum seem eager to experiment with every academic possibilty. But this is just my impression. On the other hand, I remember there were complaints about the 550K3's driveability (and the 550F2's for that matter) running a bit too lean.
Did you have the impression your carbs were opened before?
The 500K3 and the 550K3 certainly had superior silencers. They were amazingly quiet, produced a nice turbinelike sound and it's a shame you can't find them anymore. If you have them, my advice would be: no short rides. If you make long rides only, they go a loooong way. Enjoy!

[lucky]

The OP said he has the stock exhaust and the stock intake.

That means the bike probably has not been messed with.
cmyoch is doing the right things.

Still waiting to hear what size the idle jet is because that is a good clue to
nail down the year. But right now it does look like a 1977.

Almost no one changes needles.
They may raise the clip up or down, but they do not change needles.
Lets not get side tracked.

[Scott S]

Sorry, it's a 1977 cb550. I removed the needles for cleaning last night.

There were two main differences between the 77 and 78 CB550.
The 1977 was
77 CB550K X46A   14.5 float height 90 main jet 38 idle jet    3 needle position
The 1978 was
78   CB550K   PD46C  12.5 float height   90 main   42 idle   NA(not adjustable)


Look at the numbers again. What are they,do you think?
Use a magnifying glass if needed.

 My '78 550K has the PD46C carbs and it has adjustable needles. I need to dig around and find it, but I have the needle and slide #'s somewhere.

[Scott S]

 And, BTW, that pic show the stock setting for the PD46C carbs.

[ANDY W]

My PD46C carbs also had adjustable needles and the clip was in the second position from the top when i took them apart. Its tough to find the correct info on PD46A and C carbs

[cmyoch]

Thanks for the input guys! I didn't get a chance to look at the jet sizes late last night. I'll get the numbers and report back this evening. I'll also get the number off of the needle for you. The more I look at the carbs the more I believe that these were untouched. Unfortunately, I only have the carbs. My brother has the rest of the bike so the specs off the tag on the neck is not readily available. I was only adjusting the clip position due to the fact his jet kit called for the adjustment due to his intake/exhaust modifications.

I started another thread last night stating that the screws holding the arm to the slide barrel on the #4 slide stripped which put this project at a stand still. I considered switching the #1-3 back to the original position (second from the top) and only replace with the jets provided and hope that adjustments to the air mixture screws would solve any lean/rich issues. The only way I can now adjust the #4 slide position is to either drill out the screw which scares the hell out of me or search for a replacement slide and arm set up.

[Deltarider]

My guess is differences in the 550K3-4 needle clip position correlate with the size of the slow jet and the float level used in that particular carbmodel.

[ANDY W]

If he changed the intake and exhaust the you'll definitely want to be able to move the needle position. An EZout would work but I don't think you'll have the room. The only way I can think of is to drill it out, if you get a left handed drill bit it might back out while you are drilling

[Scott S]

 FWIW, these carbs aren't as lean as everyone thinks.

 I went with a 1.00mm over bore, mild port and polish on the head, match ported manifolds, CB650 cam, UNI filter in stock air box and Jardine 4-1 exhaust.
 I started out raising the needles and going fat on the mains and the bike didn't like it. No top end, wouldn't reach redline.

 After going back and forth with needles and jets, timing, mixture screws, etc., I ended up at near stock settings, with only slightly richer on the idle mixture screws and a 95 (instead of 90) on the main. This is the best the bike has ran.  Try leaving the needles in the stock position if you have one screwed up.

 Exactly what changes has he made?

[cmyoch]

I wish I was home right now to report exactly what size jets I'm putting in. I'll definitely report what was originally in the carbs and what was given to me to install. I'm still leaning towards going back to stock needle heights and try to compensate with the mixture screws.  I don't know his riding style but I think this is going to be more of a cruiser than

I have a '78 Yamaha XS650 that at one time I planned on going all custom with. I did a complete 180 and stuck with the original air box/exhaust setup and only customized the bike with a flatter seat and new bars. Performance ended up being more to my liking than how bad ass I looked on the street. Plus, I didn't want to keep yanking my carb set to make adjustments to get her to run right. Just my two cents.

[Scott S]

 XS 650 carbs are much more forgiving.

 And FWIW, the mixture screws only come into play at idle and just above.

[lucky]

FWIW, these carbs aren't as lean as everyone thinks.

 I went with a 1.00mm over bore, mild port and polish on the head, match ported manifolds, CB650 cam, UNI filter in stock air box and Jardine 4-1 exhaust.
 I started out raising the needles and going fat on the mains and the bike didn't like it. No top end, wouldn't reach redline.

 After going back and forth with needles and jets, timing, mixture screws, etc., I ended up at near stock settings, with only slightly richer on the idle mixture screws and a 95 (instead of 90) on the main. This is the best the bike has ran.  Try leaving the needles in the stock position if you have one screwed up.

 Exactly what changes has he made?

Good info Scott.

The OP said in the first post on this thread "stock intake and exhaust."

Now he says, "I was only adjusting the clip position due to the fact his jet kit( from who), called for the adjustment due to his intake/exhaust modifications."


I believe Scott and Award 50 know what they have and they must be right about that clip position.

But we still do not know what carbs the OP has.
The information is still not solid cheeeessshhh!!!

I keep forgetting it is a CB550.  IT is isn't it?

Carb PC46A?
Now I want to see a photo of the bike and the carbs.

[lucky]

I wish I was home right now to report exactly what size jets I'm putting in. I'll definitely report what was originally in the carbs and what was given to me to install. I'm still leaning towards going back to stock needle heights and try to compensate with the mixture screws.  I don't know his riding style but I think this is going to be more of a cruiser than

I have a '78 Yamaha XS650 that at one time I planned on going all custom with. I did a complete 180 and stuck with the original air box/exhaust setup and only customized the bike with a flatter seat and new bars. Performance ended up being more to my liking than how bad ass I looked on the street. Plus, I didn't want to keep yanking my carb set to make adjustments to get her to run right. Just my two cents.

"I wish I was home right now to report exactly what size jets I'm putting in."

Seems like a strange statement that you do not know what size jets you are putting in.

I wish you would tell us the whole story from the beginning.

Are you in the military?
Are you overseas?
Wish we could help more.

[cmyoch]

Lucky, I plan on posting as much information as I can to help answer my questions. I'm at work right now and I'll post info on the stock jet sizes, jet sizes that were in the kit, and the origin of the kit. I'll look back at my original post to see if I stated the origin of this project.

My brother acquired a 77 CB550, bone stock, barely running. He is doing some sort of custom project with it cosmetically along with pod filters and 4 into 2 exhaust which I believe are straight pipes. Given I resurrected and restored my '78 Yamaha XS650 and most recently a '76 GL1000, he asked that I help him with the carbs. He ordered the jet kit and handed me that kit and the carbs and that was it. I'm not in possession of the entire bike, just the carbs, kit, and instructions on the kit. I understand your frustration that I didn't post every bit of information early on and I apologize for that. Please don't convey to the entire board here that there's something fishy going on or that I'm somehow incompetent. I never paid attention to jet sizes because they were already ordered, it's not my bike, I really didn't have any reason to open the package until I'm ready for assembly.

I'll take photos of what I have to help you guys to help me out. I did take a pic of the carb body number and posted earlier in this post. I just looked and I whole heartedly apologize that I posted the wrong info. It's a "PD", not a "PC". In my haste to type up the post, I misspelled. Based on what has been given to me so far, I believe that the second to last clip position is the factory setting here. Unfortunately since the last slide I worked on stripped out, I'll have to figure out how to extract those screws if you guys think that a needle adjustment is necessary based on the jet sizes that I'll post later on today.

Again, I appreciate all the help I'm getting here. If it wasn't for the XS650 forums and the GL1000 forums, I wouldn't be where I am today with my bikes. There's more value in all of these groups than one can ever imagine!

[cmyoch]

Okay, I'm home from work and the information I neglected to post earlier.

Jets I removed were all 90's
Jet kit comes from 6 Sigma Racing
Jets in the kit are 105s for the two outer cylinders and 107.5 for the inner two cylinders
There are also 2 102.5s and 2 110s which I assume are included in case it still runs too lean?
The kit called for the slide needle clips be moved one position down to heighten the needle.
The needle number is E23501 (Barely legible even with a bright flashlight and a magnifying glass) The E could very well be a B. 

Anything else I may be missing to help troubleshoot this?

[Scott S]

 Why all these big changes?


 What intake, exhaust, etc., are you running? What makes you think that you need to make BIG changes on the jetting?

[cmyoch]

If it were my bike, I'd leave everything stock, restore to her original glory, and ride! My brother ordered the kit based on (what I assume) is a suggestion by who knows where or who knows who that if he's going to run pod filters and 4 into 2 straight pipes that this is what mods were needed.

Maybe I'll just leave everything stock, finish my clean up for him and install. If he runs into problems we can slowly work on what mods would be necessary. I thought the jets were quite different based on the sizes that I gathered up today. I've never customized my bikes to this extent by removing air boxes and changing up the stock exhaust. So I'm not very knowledgable when it comes to carb mods. I think these bikes run fine in their stock configurations.

Anyway, do you think I should stick with the stock jets and settings? I can gather detailed information on the brands of pod filters and the exhaust if it helps?

[TwoTired]

If the commitment is firm to alter the induction (shortening and adding more filter membrane area), as well an reducing exhaust back pressure), it is almost certain that stock jetting will change from those effects to be too lean for a proper running.

The main should increased in size and the slide needle raised to restore fuel mixtures to pre-mod levels.  You will also likely need to find a new idle mixture screw setting (more turns from stock).

Since "Pods" is a style rather than a specification, and there are many brands a manufacturing examples, no data for their operation exists or is published.  The exact degree of change will therefore be unique for the particular combination of parts that were chosen.  he engine will need to be tested, either by dyno and a fuel map readout, or test track, and spark plug deposit reads, to determine what the resultant mixtures are and then recursively changed and checked until something approaching the correct is found.

[lucky]

Lucky, I plan on posting as much information as I can to help answer my questions. I'm at work right now and I'll post info on the stock jet sizes, jet sizes that were in the kit, and the origin of the kit. I'll look back at my original post to see if I stated the origin of this project.

My brother acquired a 77 CB550, bone stock, barely running. He is doing some sort of custom project with it cosmetically along with pod filters and 4 into 2 exhaust which I believe are straight pipes. Given I resurrected and restored my '78 Yamaha XS650 and most recently a '76 GL1000, he asked that I help him with the carbs. He ordered the jet kit and handed me that kit and the carbs and that was it. I'm not in possession of the entire bike, just the carbs, kit, and instructions on the kit. I understand your frustration that I didn't post every bit of information early on and I apologize for that. Please don't convey to the entire board here that there's something fishy going on or that I'm somehow incompetent. I never paid attention to jet sizes because they were already ordered, it's not my bike, I really didn't have any reason to open the package until I'm ready for assembly.

I'll take photos of what I have to help you guys to help me out. I did take a pic of the carb body number and posted earlier in this post. I just looked and I whole heartedly apologize that I posted the wrong info. It's a "PD", not a "PC". In my haste to type up the post, I misspelled. Based on what has been given to me so far, I believe that the second to last clip position is the factory setting here. Unfortunately since the last slide I worked on stripped out, I'll have to figure out how to extract those screws if you guys think that a needle adjustment is necessary based on the jet sizes that I'll post later on today.

Again, I appreciate all the help I'm getting here. If it wasn't for the XS650 forums and the GL1000 forums, I wouldn't be where I am today with my bikes. There's more value in all of these groups than one can ever imagine!

Thanks for that information. Now I have a clear picture in my mind about what is going on. Thanks. I never thought anything fishy was going on.

[Deltarider]

The needle number is E23501 (Barely legible even with a bright flashlight and a magnifying glass) The E could very well be a B.

Just my curiosity: it couldn't be  E2350F, could it?

[cmyoch]

TwoTired-very good information, I seriously doubt that he is going to go through the trouble of putting the bike on a dyno and go through all the motions to properly tune this bike to optimum performance. My read on this (this is totally a guess based on how well I know him) is that he is going to cruise on it, take a day trip every now and then, and not take it to a track. I assume he's looking to ensure that the bike is going to perform well with the mods and not run and sound like crap on the road (popping on decel, etc.)

Lucky-I apologize, I responded while at work, under stress, etc. I'm also frustrated that I took on what I thought was going to be a quick and dirty clean, set everything to factory spec, and hand it back kind of job. I have a hard time handing over a set of carbs tuned for factory spec knowing good and well it's not going to be right then being called later on because the bike ran like crap. I messaged him yesterday asking more specifics about the intake and exhaust. All I got was the pods were foam no name brand off the shelf at a local bike shop and the pipes were cb drag pipes he bought off the local Craigslist. So basically, there's nothing to really work with.

Deltarider- It could very well be E2350F. I had a very difficult time reading the numbers, even with a bright flashlight and a magnifying glass. Maybe half of the "F" was worn off?  I can pull a needle out of a different slide and see if I can read it easier.

[ANDY W]

Like TT said no two pods or exhaust are the same. I don't know why the kit would haveyou install different size jets on the two center carbs, the intakes are the same length, so there would be no need. I think I would start with the 105 mains, 2nd clip position from the bottom on the needles and maybe 4 turns out on the idle screws. Better to be fat then to lean. Spark plugs are easy to change. Popping on decel may sound cool but its not good

[cmyoch]

Thanks for the suggestion. The clip was originally in the second position from the top and I moved them one position down to the center. I can easily move them one more position. That is, until I free up the fasteners on the #4 slide. Those screws stripped and I have to figure out how the heck I'm going to free them. I'm a little scared to drill them for fear I'll screw things up. Hopefully I can find a replacement slide assembly soon.

[ANDY W]

Your more likely to find an intire carb then just a slide. The PD46 carbs were only used on 77 and 78 model years and I'm pretty sure the slides are the same in the A and C carbs. Once u drill the head off the screw the rest of it should just twist right out. just take your time when drilling. Remember slower is better when drilling metal

[Bankerdanny]

Like TT said no two pods or exhaust are the same. I don't know why the kit would haveyou install different size jets on the two center carbs, the intakes are the same length, so there would be no need. I think I would start with the 105 mains, 2nd clip position from the bottom on the needles and maybe 4 turns out on the idle screws. Better to be fat then to lean. Spark plugs are easy to change. Popping on decel may sound cool but its not good

Glad to see someone else comment on this. I suppose that during the tuning process it may turn out that one carb may need slightly different jetting than another, but I cannot imagine why you would start out that way. The presence of pairs of jets makes it seems more likely to me that your jet kit is for a twin and not a 4 cyl.

[Deltarider]

I know, these little screws are a pain. Years ago I almost stripped one myself. What is the recommended type of screwdriver for those screws?

[Bankerdanny]

Technically I believe they are JIS style, which looks like Philips, but is shallower and has squarer shoulders than a philips.

Just search JIS in eBay and you will find several options. I picked up a 3 screwdriver set earlier this year for about $20. If you have an old Jap bike it's a worthwhile add to your tool chest.

[cmyoch]

I used a JIS driver on them but it was the worst carb out of the set so they must be corroded in there. I'm on the search for a left handed drill bit to try to back them out if I'm so lucky.

In the instructions in this kit, there was a summary of the questions I guess were asked when ordering. It was noted that the bike was a CB550 with 4 carbs. It specifically stated in the instructions that there were different jets for the outer 2 carbs and inner two. Maybe air flow due to pods on the inner two play some sort of role in that??

BTW, I was at a local Rural King and looked through the clearance tool bin and got my set of JIS drivers for $10. Couldn't resist. Before these, I had a driver bit that came in a socket set I had. It had a blunt tip and fit the heads on both my bikes perfectly. A lot of us probably have a JIS bit somewhere and don't even know it.

[lucky]

I know, these little screws are a pain. Years ago I almost stripped one myself. What is the recommended type of screwdriver for those screws?

A #2 phillips will work perfect.

Use a long screw driver.
Make sure you have the screwdriver lined up,not on an angle.


If you use a #1 phillips it WILL strip the screw.

[TwoTired]

TwoTired-very good information, I seriously doubt that he is going to go through the trouble of putting the bike on a dyno and go through all the motions to properly tune this bike to optimum performance. My read on this (this is totally a guess based on how well I know him) is that he is going to cruise on it, take a day trip every now and then, and not take it to a track. I assume he's looking to ensure that the bike is going to perform well with the mods and not run and sound like crap on the road (popping on decel, etc.)

The bike is doomed to be a status statement only, imo.  The test tack (rented or chosen from street availability) is just to dial in the carbs for the mods.  Similar to what Honda did to choose the original carb set up.  Yes, it is a pain to re-jet properly, but it is an artifact of the choice regarding pods and exhaust changes from stock.

Anything you do to the carbs will be based on hope and luck toward getting correct mixtures.  Without testing and adjusting, the best you can hope for is lack of rider complaint.

In the very old days when people were finely tuning the carbs for max power, the inner cylinder often ran hotter than the outer cylinders.  Since some of the cooling of an air cooled engine comes from the fuel entering the cylinders, a richer mixture would help cool the inner cylinders.  So, larger jets were used for inner cylinder carbs.  Honda never expected the engine to be run flat out for long durations.  So, all the jets are the same size the cooling fins are relied upon to keep all the cylinder at even heat levels.