Topic: PD46C tuning

[AlekStooge]

Today I'm starting to set up my carbs. Here is what my set up is going to be and what information I gathered from the forum in doing this correctly. I know Honda engineers decided that the stock air box is truly best for these bikes and I'm going against what is recommended by the forum members. I've heard it before on here so I don't need to hear it again but clearly there is a way to correctly tune for individual filters (opposed to just throwing them on and expecting it to run smoothly) and I plan to do so with the information I've gathered. Please tell me if I'm on the right track and what I can do to make the process more through and results more accurate.

Here are the details of my setup:

PD46C carbs
MAC 4into1
Main jets 105s ( I have 108s in case)
Pilots stock 42s ( I was told not to up these to 45 as the aftermarkets don't live up to the originals quality and the IMS can be tweaked to compensate)
IMS one turn out left
Shimmy the needle to the third setting from the top.
Adjust the floats to about 12.5mm or at least have them close and all equal.
Chicagoland elevation no other adjustment needed. 600ft above sea level.

Yes the carbs have been cleaned. Carb cleaner was sprayed through both jets, needle jet holder, IMS, air Intake, and float bowls. After that I used a carb wire cleaner through the small openings. I not sure where the emulsion tubes are so I couldn't cleaned them, I thought they're in the needle jet. 

I don't have a carb synch yet but will get one when the bike starts.

I didn't adjust the points. I started to take it off one day and an old man behind me yelled no don't touch that! I put it back on and I'm not sure what to do here with the points.

I just got a new tang for my float bowl after loosing the little spring that is impossible to find if dropped! I am ready to adjust the floats but I'm not 100% sure how to adjust them? Once adjusted do you measure from the base of the float bowl to the upper end of the float?

What order do I make these changes. I have a pen and notebook ready to record results, I just don't know which one to start with? I don't want to do all of them at once, so I can avoid ambiguity. I plan on doing one modification at a time.

I did buy one 42 non Keihin pilot jet though because one of the originals looked dilled. (See photo)

I used this page on the forum http://forums.sohc4.net/index.php?topic=98867.0 as well as Denny Zanders jetting guide for my info.

(Won't allow me to attach pilot jet photo. This is a frequent problem I'm having it just takes me to a blank post a new topic screen. Sorry guys)

[harisuluv]

Looks pretty close.

105 main is good, sometimes people need 110.
PD46C should have the adjustable needles, so one step richer.  It's the 750 PD carbs in 78 that don't have the adjustment mostly.

No idea what little spring you're talking about.  The float setting has no measurement that involves the bowl at all.  Measurements are made from the carb body to the float.

I can tell you don't want to hear "did you clean x" but 9/10 of these threads that start off with 100% positive I cleaned such and such end several pages later with "works after I cleaned x."  So you're still going to hear it, especially if you don't know what an emulsion tube is.  Did you pull your slow jets and clean then with your special wire?

[eoddom]

I don't know if the PD46A and PD46C have much in common, but if they do, read this about 10 times.

https://s3.amazonaws.com/sohc4-tech/CB550/PD46A_rebuild.pdf

To measure your float height, you would push the float up to where the float needle is fully in, but the little knobby looking thing sticking out of the end of the float needle isn't being pressed in.  You measure from the bottom of the float, to the base of the carb.

The reason these guys suggest using the stock airbox and stock carb settings is so you can make sure the bike is running 100% and all other possible mechanical and electrical issues are resolved before you start trying to tune a carb for more airflow.

Also, as mentioned, make sure everything is clean.  If those carbs have been sitting for a long time with gas, there's gonna be varnish and nastiness everywhere.  I had though I did a good job cleaning my carbs just by spraying them out good with carb cleaner and WD40 and some wire to clear out the jets, but when I drained them the other day allllll sorts of black buildup came out of the bowls that had to have been stuck in different parts of the carb.

[AlekStooge]

Looks pretty close.

105 main is good, sometimes people need 110.
PD46C should have the adjustable needles, so one step richer.  It's the 750 PD carbs in 78 that don't have the adjustment mostly.

No idea what little spring you're talking about.  The float setting has no measurement that involves the bowl at all.  Measurements are made from the carb body to the float.

I can tell you don't want to hear "did you clean x" but 9/10 of these threads that start off with 100% positive I cleaned such and such end several pages later with "works after I cleaned x."  So you're still going to hear it, especially if you don't know what an emulsion tube is.  Did you pull your slow jets and clean then with your special wire?

The little spring is attached to the float valve needle to stop the float from dropping. Its not actually a spring, anyways I got a new one.

I cleaned the carburetors to the best of my knowledge. The slow jets were cleaned and my mysterious special wire is a wire cleaner set from K and L, which I got on 4into1.

I don't know if the PD46A and PD46C have much in common, but if they do, read this about 10 times.

https://s3.amazonaws.com/sohc4-tech/CB550/PD46A_rebuild.pdf

To measure your float height, you would push the float up to where the float needle is fully in, but the little knobby looking thing sticking out of the end of the float needle isn't being pressed in.  You measure from the bottom of the float, to the base of the carb.

The reason these guys suggest using the stock airbox and stock carb settings is so you can make sure the bike is running 100% and all other possible mechanical and electrical issues are resolved before you start trying to tune a carb for more airflow.

Also, as mentioned, make sure everything is clean.  If those carbs have been sitting for a long time with gas, there's gonna be varnish and nastiness everywhere.  I had though I did a good job cleaning my carbs just by spraying them out good with carb cleaner and WD40 and some wire to clear out the jets, but when I drained them the other day allllll sorts of black buildup came out of the bowls that had to have been stuck in different parts of the carb.

So you don't measure the floats when they are hanging? How do you actually adjust them? I messed around with it before but don't remember how it was done.

Can someone please tell how to remove the emulsion tubes so they can also be cleaned. Thank you.

[eoddom]

Take a picture of where your jet screws in and post it please.  If it's anything like the PD46A, the emulsion tube is what the main jet screws into.  It should screw right out of the carb body.

[AlekStooge]

Take a picture of where your jet screws in and post it please.  If it's anything like the PD46A, the emulsion tube is what the main jet screws into.  It should screw right out of the carb body.

I thought this was the needle jet holder.

[eoddom]

That little brass tube with the holes in it is your emulsion tube.

[Bailgang]

That little brass tube with the holes in it is your emulsion tube.

Many refer to it as the jet holder as well, even on carbs where the jet is held in place by an o-ring and a piece of spring steel in the bowl as in cb500/550 or my cb350 twin it's still many times referred to as the jet holder. Go figure.

[AlekStooge]

Ok good I cleaned those. Two questions I had in the originally post were.

1. How do you adjust the floats?
2. Is there an order in which I should do the changes? I don't want to them all at once then be guessing. I plan on doing one at a time and logging results.

Thanks

[AlekStooge]

Oh ok you put pressure on the tang to bend it.

[DaveBarbier]

Before messing with the carbs you need to learn to adjust the point gap and timing. It's in your service manual.

The carbs can't just be cleaned to the "best of your ability", they need to be spotless. If not and you have running issues, you'll be chasing your tail. Remove all jets...that includes the pressed in pilots. Use your special wire and carb cleaner and make sure all galleries are clear.

I have PD46C carbs on my '78 550 with 4-1 and velocity stacks. Very similar to your setup. Actually, you know this because we've spoken about it. When I was setting mine up Harisuluv gave me some great starting points. Here is where I ended up:

IMS-1 turn out
Main Jet-110
Slow Jet-45 (I had to use Keyster slow jets because OEM aren't available anymore as mine were all massively drilled out by the PO)
Float Height-varied (All fuel levels 4mm from bowl seam checked by the clear tube method)
Needle Setting-3rd from top

This should get you running pretty good. Or good enough to do plug chops.

As far as an order for all the things, I would do the complete 3k mile service first, then just change all the carb settings to what I listed above and then sync them with the carb sync tool you're going to get.

[AlekStooge]

@Dave

I got an moldy Clymer's manual. I'm just going to download one and starting figuring out the points. Your right that should be taken of first.

In regards to cleaning I sprayed carb cleaner in every orifice and scrubbed wire through them. The only place I didn't do was open up the top cover and spray the slide, its clean very clean there. The only other thing I can do is media blast the carbs like I've heard of people do that here but I don't know if that's necessary.

I don't have mains as big as 110s. Hopefully the 105s or 108s will do, but then again these carbs are lean to begin with. I thought you said in the past it isn't necessary to raise the pilots to 45?

[DaveBarbier]

@Dave

I got an moldy Clymer's manual. I'm just going to download one and starting figuring out the points. Your right that should be taken of first.

In regards to cleaning I sprayed carb cleaner in every orifice and scrubbed wire through them. The only place I didn't do was open up the top cover and spray the slide, its clean very clean there. The only other thing I can do is media blast the carbs like I've heard of people do that here but I don't know if that's necessary.

I don't have mains as big as 110s. Hopefully the 105s or 108s will do, but then again these carbs are lean to begin with. I thought you said in the past it isn't necessary to raise the pilots to 45?

I can't tell if you're saying you haven't pulled the pilot jets or not. You did say you unscrewed the emulsion tubes, right? Both of these have the obvious holes but they also both have tinier holes drilled latterly through them. There's no way you can clean all these holes while it's still in the carb. Pilots must be pulled to be sure they're clean.

Yeah, you're right. Usually you don't need to change the pilots for these mods. That's probably why my IMS is turned out only 1 rotation (to compensate for the increase). I bet it's better to use the stock size with a couple turns out of the IMS. But I'll defer to Harisuluv on that one.

But I did read that you have 3 Keihin pilots and 1 Keyster pilot. This can screw things up. I am 99.9% sure the Keihin's aren't available anymore so I would go with all 4 Keysters. Maybe I'll be scolded by the forums but in my mind that's better than mixing.

No need to spray under the top cap. If the slides move freely then they're good. I wouldn't media blast inside the carbs.

Makes sense?

[eoddom]

It seems your best option for cleaning would be to pull the carbs completely apart and find someone with an ultrasonic cleaner.

[AlekStooge]

I did pull out the emulsion tubes out. The confusion was I thought it was the jet holder which it is. I didn't understand there were two names for the same thing. I did pull out the pilots, mains, emulsions, needle valves, filled the bowls with carb cleaner, sprayed through the air intake...I even sprayed the IMSs. I did sprayed everything individually and wired it. Then sprayed the opening the components came out of and wired as well. As I'm writing this the only thing I sprayed carb cleaner through is the air jets but I didn't wire clean them.

Yes you understood correctly about the 3 Keihins and 1 Keyster pilot. I've never seen Keihin pilots available so they don't make them any more for our bike.

The pilot looked different from the other three. It doesn't let me post a picture of that photo, it just takes me to a blank start new topic screen.

[DaveBarbier]

That's pretty much how I cleaned my carbs and they're functioning very well. So unless someone has a better idea, I'd get all the same pilot jets...even if they're Keyster.

And don't let that old man tell you not to touch the points, haha! Besides, if you partly removed them then they have to be reset anyway. It's pretty easy if you read the manual. But I'm sure there are more step by step instructions on the forum somewhere.

Good luck

You can use a third party image uploading site like photobucket (which I hate, don't use that one) or IMGUR.com (that's a good one) and then just paste in the link for the picture.

[AlekStooge]

Thanks for all your help Dave and everyone else too.

I froze when the old man said don't touch that and laughed my ass off afterwards!

I tried using a flathead to adjust the tangs but doesn't seem to work very well is there a better tool or way to do this?

I'll keep posting to this topic when I have some results.

[DaveBarbier]

I use a small flat head. In case you missed it, use IMGUR.com to upload your pictures then just paste the link.

[AlekStooge]

[Lostboy Steve]

Anyone on here use a Wide Band to tune their jets or do we all do it with plug chops and seat of our pants? I've been wanting to buy an Innovate LM2 for years. Maybe its time. Also, has anyone tried to weaken the throttle return spring at all to ease up the throttle pull?

[AlekStooge]

Can someone double check my work. 2,3 and 4 are adjusted to 12.5 mm. 1 appears to be bent. I already tried to bend it straight with a hammer. I don't want to wait for a new float to come in because I want to move forward tomorrow. Any suggestions?

[harisuluv]

It looks like you are setting the floats backwards.  In other words, you are setting the droop of the float to 12.5mm or the float setting.  This isn't really what you need to do.  The last picture is the measurement you want to take, except you have them totally upside down.  You want them oriented so the float just rests or touches the tip of the spring plunger.  Normally new float valve springs are pretty stiff, but ideally you don't want the entire weight of the float resting on it like that when you measure. 

There are two tangs on each float.  The same tang that the float needle wire clip attaches to is what you need to adjust.  The other tang that makes direct contact with the float post only acts as a stop to limit them from hanging too far, i.e. excessive drop where the float valve can actually come out of the seat.

[DaveBarbier]

I already tried to bend it straight with a hammer.

Haha! That's really funny.

You should verify the fuel level with the clear tube method. On the PD46C's it's crazy easy. It's impossible for anyone to see if they're adjusted properly with a picture.

I forget, are you using aftermarket float needles? If so, the 12.5mm kinda goes out the window. I have a mix of aftermarket and stock and all my float heights are varied, but all fuel levels are dead on at 4mm from the bowl seam.

[AlekStooge]

I measured the floats with the carbs sideways (first 3 pictures). I got them so the float valve isen't being pressed in or the floats are hanging. There was no weight being put on the valve plunger. I thought this was the way to do it. So I should have the floats hanging like in picture 4? At what point of the float would I meassure then? One of the float valve plunger and spring is new because I Iost the spring in the past rest are stock.

[DaveBarbier]

The way you're doing is right. Float tangs just barely touching the plungers while the carbs are on it's side. Harisuluv can verify but I think with the flat floats like we have you measure from the highest part (furthest away from the bowl seam).

I would set them to where you're satisfied and then check with the clear tube method. If they're off, then adjust again. I think people rig up a little stand so they can add fuel while the carbs are off the bike. I do it while it's on the bike because I do things the hard way and I don't care and then I drink after to forget.

This is what my fuel levels look like, yours should be the same. 4mm.