Topic: PD46A Inspection and MAC 4 into 1 help

[ShovelHeadNed]

I dissembled my carbs (PD46A) tonight on my 77 550K and found that for the most part things were not too bad, but I do need to replace a few parts. Before I start purchasing parts I wanted to get a consensus on what jetting I would need for a MAC 4 into 1 exhaust which I have already ordered. I've been searching high and low for answers but not finding anything that pertains. Can anyone with this setup help?
Also is there anywhere that carries parts for the PD46A carbs.......These 77/78 models are a pain in the neck to find parts for.

[harisuluv]

Stock jetting is probably fine for a mac.

[ShovelHeadNed]

That would be excellent if that is the case because I am having a hard enough time finding stock parts for these carbs let alone anything else.

[kerryb]

I suggest you try Sirius for the carb parts.  just don't ask me how to use their website, I was a complete failure at that.  They did however have all the parts I needed for my '78 750k PD carbs.

just for fun...kb

[MiGhost]

Everything you need to rebuild your carbs will still be available through Honda. If you are having trouble sourcing parts through your local dealer. You can get them through an online source such as partzilla.

http://www.partzilla.com/parts/search/Honda/Motorcycle/1977/CB550K+A/CARBURETOR+COMPONENTS+77/parts.html

Replacement jets are available through jetsrus
http://jetsrus.com/a_jet_kit_street/honda_550_CB550_1977-1978.html

or Sirius Consolidated Inc.
http://www.siriusconinc.com/search_result.php?make=1&model=cb550&part=1&partno=&search=search&x=41&y=7

[ShovelHeadNed]

excellent thanks very much

[Stoli]

After I rebuilt my '78 CB750K, I ran a Mac 4-1 with the stock air box for a few hundred miles and it ran a little lean. After hours of reading threads on the subject, you will find that results will vary, so just throwing that out there. Your stock jetting may be fine.

If you are not changing the air box, then the slow jets should be fine (which is good because they are pricey). A less restrictive exhaust tends to affect 1/3 to wide open throttle, which requires an increased main jet and possible needle position adjustment. If you stick with the MAC baffle, I think the most you would have to do is up the mains one size. If you change to a less restrictive or no baffle then you will definitely need larger mains.

I found main and slow jets for the PDs at jetsrus.com.

[ShovelHeadNed]

Thanks...there is a chance I may want to remove the baffles so this is good information.

BTW does anyone know of a good method for doing an overall cleaning of the carbs, like a 24 hour soak of some kind. I'm thinking of trying the PineSol method, but just wondering what has worked well for others since the outsides of my carbs are pretty grimy

[Stoli]

Can't help you there. I had an old can of carb cleaner that I soaked mine in. If your carbs have been sitting for a while, consider pulling out the pressed in slow jets to clean them. You can't really clean them thoroughly unless you remove them.

[flybox1]

pine sol with fcuk them up. dont use it. use simple green or a carb chem dip, but a dip/soak will not clean them adequately.
without de-racking the carbs from each other, you'll need to take them apart and clean/clear all the passages, paying particular attention to the accel pump circuit, the tow one way valves (at the top of the #2 carb bowl and in the bottom of the accel pump bowl) and the pump jets (squirters) in the carb throats.  pull out the pilot jets for a cleaning, and remove the main jets and the emulsion tubes they are connected to.  get them spotless, inside and out.
replace the accel pump diaphragm if it is torn or cracked.  if it is good, clean its 'mickey mouse' ears.  Or, jsut replace it with a new one, they're cheap and are an integral part of your carbs and 'spirited' acceleration. 
one word of caution, the diaphragm will melt when in contact with carb cleaner.

My jetting is in my signature. I have a more restrictive exhaust than a baffled mac.  its slightly rich at all throttle positions, and it seems to like it that way.
Sirius has all the jets you'll need.

[TwoTired]

Stock jetting is probably fine for a mac.

Sorry, I'd have to disagree with that.  PD carbs were only used on machines with a high pressure exhaust system.  The MAC is in no way a high pressure exhaust.  So, the carb's main should be bumped up to #95 or even #100, and the slide needle raised a notch as well (just an educated guess).  Gonna be a test and try recursive operation.

However, without carb enrichment, the engine will run lean and hotter than is recommended.  Baffle removed will make matters worse.  Induction changes even moreso.

The slow jet size will likely be ok, though I prefer the #42 from the C model, but you will certainly need to find a new pilot screw setting.  Exhaust (and induction) changes are not just cosmetic or "style" choices, as these parts have a functional contribution to engine operation.

Dumb to use pine sol on carbs, imo.  Acids AND bases dissolve metal, as well as dirt and grime.  I prefer to preserve the metal.  Carb cleaners are ph neutral, so they attack bits that aren't metal (rubber and plastic included).

I don't believe in dipping the carbs either, as this in no way ensures that small passages and orifices are properly cleaned.  Attention here is key to success.

[mono]

I've soaked a set of "hopeless" carbs in 50/50 PineSol/water, and it's really good at cleaning out the old gas varnish and any grease/dirt that's on them.  Smells spring fresh too.  That said, I would not soak them for more than overnight -- as the other guys said, it's slightly acidic and could screw stuff up over long exposure, especially with differing metals in the carbs.

I did not notice any damage to mine, and I had soaked them for 3 separate overnights, rinsing/scrubbing/washing between each soak.  your results may vary.

unless they're really really gross, stick with carb cleaner and elbow grease.

[ShovelHeadNed]

Stock jetting is probably fine for a mac.

Sorry, I'd have to disagree with that.  PD carbs were only used on machines with a high pressure exhaust system.  The MAC is in no way a high pressure exhaust.  So, the carb's main should be bumped up to #95 or even #100, and the slide needle raised a notch as well (just an educated guess).  Gonna be a test and try recursive operation.

However, without carb enrichment, the engine will run lean and hotter than is recommended.  Baffle removed will make matters worse.  Induction changes even moreso.

The slow jet size will likely be ok, though I prefer the #42 from the C model, but you will certainly need to find a new pilot screw setting.  Exhaust (and induction) changes are not just cosmetic or "style" choices, as these parts have a functional contribution to engine operation.

Dumb to use pine sol on carbs, imo.  Acids AND bases dissolve metal, as well as dirt and grime.  I prefer to preserve the metal.  Carb cleaners are ph neutral, so they attack bits that aren't metal (rubber and plastic included).

I don't believe in dipping the carbs either, as this in no way ensures that small passages and orifices are properly cleaned.  Attention here is key to success.

Just purchased some #98 Mains as a good safe number in between. I throw those in and see how things go.

[motosan]

No doubt, you will definitely need to put a bigger jets for both.

I have almost the same setup, PD46A and MAC 4-into-1, but with fiberglass exhaust wrapping on it, and everything else stock.

Even without the fiberglass wraps, I had to bump both jets up.  With exhaust wraps , 40 was a-ok, but RPM was often very slow returning to idle speed when the engine has warmed up fully....which I think is a sign of lean...so I'm changing them to 42.  So.....with your setup, I think 40 should be ok but I'd actually recommend 42.   

For main jets....you might want them bigger than 98....possibly 102.  With exhaust wraps I'm using 105 main and needle clip at the lowest position.   

One last think I want to mention is....it's an old engine, i think it's better to be little rich and lean.    Good luck!

[Scott S]

 I found that the PD46C carbs on my '78 (very similar to what you have) didn't need NEARLY as much jetting as you would think.
 My engine has a 1.00mm over bore, ported/polished head (mild), match ported manifolds, UNI filter in stock air box and a Jardine 4-1 with baffle.
 
 I started very rich since these are the "lean burn carbs"; 110 mains, raised the needles one clip, mixture screws, etc.
 After a lot of fiddling and tuning, I ended up back at ALL STOCK settings except for a 95 main (vs. 90 stock) and slightly richer on the idle mixture screws.

 I'd say give the stock jetting a try with the MAC exhaust. The MAC seems to be very forgiving as far as jetting is concerned.

[brewsky]

Thanks...there is a chance I may want to remove the baffles so this is good information.

A MAC with the baffle removed is unbearably loud, and will screw with the jetting.....if you just want some more noise, might try their "performance baffle"
Or, you could mod (open) the stock baffle with little noise increase
http://forums.sohc4.net/index.php?topic=106651.0