Topic: Mini project PD46C rebuild

[AlekStooge]

I asked my friend if he'll let me/teach me how to use his ultrasonic cleaner. He said yes, so I decided I'm going to rebuild my carbs. I thoroughly cleaned them and replaced components but not rebuilt.

Here is the back story. I ran my bike and it was running erratically at moments and stable at others. I thought it was burning oil after a engine rebuild per the plugs. I bought a Motion Pro compression guage, I wasn't able to make a leak down tester. No compressor.

Worst one of the 4. Wipes down easily though.



After about 20-25 kicks per cyclinder, these are the highest numbers I got. Wiseco 10:1, valve lash backed off, and no carbs.
1-195
2-194
3-196
4-195

I was certain it was oil burning from the plugs. I was afraid that oil was sealing the rings but Sean Barney said no way it's carburation.

I ordered from Jetsrus, Keihin mains 100-110, pilots 42 and 45 (their "quality" reproduction), Keihin float needle valves and a jet case to store them all! I wasn't able to find other genuine components but I have a full rebuild kit from 4into1 that I could make the best of. I think I have everything I need.


I'm gonna start disassembling the carbs tomorrow for the ultra sonic cleaner. It doesn't look too difficult except the throttle spring. I don't like to put springs back on. My plan is to bag everything up in 4 larger and 4 smaller bags for different size parts.

Up front I have a few questions:

Best way to handle disassembly of the spring?
How far disassembled do carbs need to be for ultra sonic cleaning?
Any parts that can't go into the cleaner, like rubber material obviously?
What is typically done for metal parts like the air tubes, connecting tubes, throttle, choke hinge and idle adjustment? There is rust. I'm thinking plating and painting.
Anything else I need to know about ultra sonic cleaning or restoring carbs?

I'll post pictures of the carbs tomorrow.

[FourUsTry]

I just finished a PD46C full teardown rebuild for a stock '78 550K. (Didn't test them yet but I'm hoping my starting woes are over.) Since my airbox/exhaust is stock I just cleaned up the existing jets and reused them, but otherwise I'm glad to help with questions. Mike Nixon helped me out generously with advice.


The throttle spring was no problem to rewind/reattach after getting the throttle shaft reinstalled.
The choke shaft springs/config took a few tries to get right so take careful pics of that before the teardown.
I was suspicious that the 12.5mm float height spec was a typo and should be 14.5mm like the '77 because others here said ~14.5mm was what they found in their carbs and because 12.5mm requires a noticeable slope to the float bottoms, but Mike Nixon confirmed that he has used 12.5mm (measured in the middle of the floats) and the carbs work that way so I went with that.
The o-rings on the fuel connectors are good to replace and they should be in your kits: you can probably do this without de-racking but you'll have to release the slide linkage from the throttle shaft and remove the choke plates to slide them apart enough to change the o-rings.
Doing a full teardown would let you replace any worn out felt washers but that job I found to be a b!tch so don't do it if your household doesn't like cussin'.
I put the rusty parts in EvapoRust and I put a high temp clear coat on some of them but obviously replating is better.
I found a source for the vacuum tube (skinny) connectors but the "OEM" replacements were just sections of tubing.


Let me know if I can help with other questions.

[AlekStooge]

Thanks, for lending a helping hand!

I believe I have to de-rack in order to get it in the ultra sonic cleaner. Yeah it's 12.5mm I had it set, but where did I put that float guage? Clear tube method seems popular on here so I'll have to learn that.

I have the slide linkages disconnected. Does 2 not have a spring tensioner because it is the master?



This fell out after I took a break. I don't know from where or what it is? Looks like a crushed o-ring.

Other than that I got things bagged up nicely.

Carb 3 is the only one that is problematic, I had to drill out the throttle shaft screw. Someone used a Philips, might have been me before I learned the dark art of using JIS screwdrivers. More on that later.

[Darren Jakal]

Thanks, for lending a helping hand!

I believe I have to de-rack in order to get it in the ultra sonic cleaner. Yeah it's 12.5mm I had it set, but where did I put that float guage? Clear tube method seems popular on here so I'll have to learn that.

I have the slide linkages disconnected. Does 2 not have a spring tensioner because it is the master?



This fell out after I took a break. I don't know from where or what it is? Looks like a crushed o-ring.

Other than that I got things bagged up nicely.

Carb 3 is the only one that is problematic, I had to drill out the throttle shaft screw. Someone used a Philips, might have been me before I learned the dark art of using JIS screwdrivers. More on that later.

I have disassembled and cleaned two sets of these carbs, but have not run either of them.

The second picture is probably the felt "O Rings" that are on both the choke linkage and throttle linkage. On mine the choke felts were toast, but the throttle felts were fine. I know that some have made new ones out of felt (they are pretty hard to find). I used some brass grommets and springs (see picture) on mine and seems to work (again I haven't run the bike with then on).

In your fist pick the flat connecter bar kind of looks bent.

Good luck with it, Darren

[FourUsTry]

Yes, number 2 is the master and has no adjuster. You bench and vacuum sync the others to match it.

The clear tube method is frowned upon by some carb experts. I think it is a good rough check while the carbs are on the bike but if you carefully set the float heights during a rebuild they say you don't need it. Still, it is a bit of physics fun.


That does look like a destroyed o-ring (not a felt). Not sure of the size but it doesn't look like the tiny one on the idle mixture screw so then it could be from a fuel connector tube (between the carbs) or from a drain screw (bottom side of float bowls). I hope it isn't one of the rubber throttle shaft seals on carbs 2 and 3 since they aren't available (but some claim you can use 2 o-rings to replace them).


If you don't want to make your own you can order new stock-sized felt seals from a few sources or thicker seals (have to invert the retainer cups) from Aaron at Dude's Garage   http://dudesgarage.com/4301.html
I did the thicker seals for the throttle shaft but the choke shaft retainers are hard to get out so I went with the stock thickness seals for them.
You have only 2 felt throttle shaft seals and 6 felt choke shaft seals.
I would get extras of the choke seals because they are easy to mess up as you develop the technique for getting the buggers in.


If your boots are original consider replacing them, esp. if you see cracks or have carb performance issues. You can get OEM ones for the engine side but only aftermarket for the airbox side as far as I know.


Don't rely on just ultrasonic for the jet and circuit cleaning: pull the jets and carefully clean any you aren't replacing.


Have fun!

[AlekStooge]

That definitely wasn't felt. Where are these felt o rings on the choke shaft? The chokes plates weren't off and the carbs were together when that fell out.

Clear tube method. People seem to think it's more accurate when tuning. I don't know and I don't agree it is but that's what I remember people doing.

I'm going to take a look all the o-rings and seals your reffering to later today. I have the carbs de-racked but don't see some of what your reffering to. Definitely don't see no felt.

Boots are new. I'm 99% certain OEM. I only ran them in the garage when I started the engine a handful of times.

Jets will be new and everything else wire cleaned.

Question: These are new Keihin jets I left in the bike when I stopped working on it for a long while. Is this jet discolored due to me leaving bad gas in the float bowls? I know shame on me 


What do I do about the air jets? Never worked on them. How about the bore that the needle valve blocks? You know the brass one.

That bar is bent. I was gonna ask.

I'm having fun!

[Darren Jakal]

FourUsTry is probably right about the idle mixture screw o-ring. I also found some pieces of these at the bottom of the pan when I did an initial soak of the carb bodies.

The felts are located where the choke shaft enters the carb body. I should pull out my extra set and look before I say any more.

Lots of good knowledge here!

dj

[FourUsTry]

If you don't see any fibers showing at the choke shaft holes the felts are probably all squished into their tiny groove. On the inner throttle shaft holes on carbs 1 and 4 you can probably see those larger felts: the choke ones are similar but smaller. You can get them out with a dental pick but don't expect to be able to get these old ones back in so don't fool with it unless you have new ones on order. They are only a dust (not vacuum) shield so not super critical but if you want to never de-rack these carbs again I'd suggest replacing them and all the other non-metallic bits.


The jet discoloration looks like brass oxidation but may have been accelerated by leaving fuel in them. Best carb advice is to NEVER leave fuel in your carbs for more than a couple of weeks.


Since float height doesn't directly translate into fuel level I kind of agree that the clear tube is a more direct measurement of what you are trying to set. But you can do it wrong (e.g., move the tube upward after letting it fill and thus overfilling the bowl). And if Honda raised the fuel level in the '78 model to address a lean/starting problem then the normal SOHC4.net recommendation of 2-3mm (or 3-4mm!) below the gasket line may be wrong. Best approach might be to set the float height very carefully/accurately (even out the floats and check both sides, etc.) and then do a proper clear tube test to check that they are all within a half mm of each other. But unless you have a bad/leaky float (PD46C has solid plastic floats so this isn't an issue) or a defective float needle or seat, the float height should give you very even fuel levels. The fuel level isn't super critical anyway.


For the air jets just blast carb cleaner through them a few times and make sure it comes out somewhere with a good flow. That after an ultrasonic bath should suffice unless you have major blockages, in which case you might need a stronger soak like ChemDip. I don't know if/how you can mechanically snake these circuits but a pro might be able to do it.


DJ's been at this a lot longer than me so I'm sure he has lots of good tips (too late for my PD46C rebuild!). This was my first carb rebuild and I don't know yet if was a success -- doing some other steps before I put the carbs on in the next few days.

[AlekStooge]

DJ- I see the IMS o-ring on the fiche but I don't see them on my screws or down in the bore.



I believe I found the felts. 8 total? Two on the outer throttle shaft carbs and six on the choke shaft?

I see what you mean about it being a drag to replace them. I want to leave it alone but I would have to only partially dip the carbs in the cleaner. I looked at carb 3 felt. It is partially rotted. Hard to take pictures (let me know if you want to see more).

What am I going to do, if they don't exist?

I'll handle float setting later. Good read though. So how are air jets adjusted is that done when vacuum synching? I have Bikemaster guages but never have done it.


I think I'll leave the choke assembly alone and just put it in the cleaner. That outer spring seems super fragile.

What about this varnish; does the cleaner typically get it? I have media blasting capability available to me if needed.

[FourUsTry]

There should be a spring, washer, and then o-ring on each IMS. My carbs were missing the washers so I ordered a pack of them. My o-rings were stuck down in the hole and I had to fish them out with a dental pick so look and poke around carefully down there to see if yours are hiding.


Yes, there are 8 felt seals: 2 x 11mm on carbs 1 and 4 throttle shaft holes and 6 x 6mm on the choke shaft holes.


As far as syncing, after you rebuild them do a bench sync by setting the slides to the same height as carb 2 using the adjuster screws/nuts on 1, 3, and 4. You can use the big idle screw to set carb 2 to a known size, like the width of a drill bit. Be careful with the drill bit not to damage the slide or carb bodies: just get a slight drag fit on each slide. The bench sync gets you close but for best results once they are installed you remove the silver sync screws and attach your carb sync tool to them and follow the normal vacuum sync procedures.


That doesn't look very varnished to me. If the ultrasonic doesn't do the trick you can always do the media blast but you have to be careful to get any media out of all circuits. Or you can just polish the bowls with a dremel polishing wheel or Q-tips in a drill with a SMALL amount of compound.

[Darren Jakal]

As I recall I did need to get into the IMS holes with a pick to get the old remains of the o-rings out.

As for float height I did find conflicting numbers, and after doing both sets of carbs I just went with what they were set at ( don’t remember the actual number) as they were almost all the exact same with no evidence of tampering except for one. This one had a leaking float valve and the PO tried to fix the problem by bending the float tab and did a bad job of it. I bent it back to the original shape and left the rest alone and found a replacement valve that fixed the problem. For the life of me I don’t really understand how these float tabs could be off in the first place.

I found lots of info on float height, but not one instance of how to actually bend the tab correctly. The one that was altered in my carbs was badly twisted, but all others were straight and the same so I went with that.

Hope this helps, dj

[AlekStooge]

My washers aren't there either. I think they'll be in my rebuilt kit. I'll look.

At least now I have the sizes for the felt seals. I'm taking my carbs over to beer Friday, same place as the ultra sonic cleaner. Lot of knowledge there, I'll ask about the felt washers. I think they are doing a /2 sidecar conversion.

For adjusting the float down. I remember doing that with a precision screwdriver wedged between the float towers that the shaft slides into. Of course these are set pretty high so if anything they are adjusted up.

Speaking of that shaft and POs

When I replaced one of my floats with an aftermarket float. The bowl wouldn't meet the surface. It turned out to be the shaft that came with the float was a hair longer and it was blocking the bowl from being installed. I just swapped it out with the old one. Here is a thread I did on that, page 2.
http://forums.sohc4.net/index.php/topic,152729.msg1745448.html#msg1745448

As for the PO brace yourself. I'm warning you...










Looks they tried to drill them or just made a slot to take it out. At least be consistent and do it to all of them

[Darren Jakal]

Yea that’s not pretty. The first set of carbs I did I don’t think anyone was inside messing with it so I just went with the float height as they seemed unmolested. The second set had the one float tab that was twisted but it was also the one with the leaking float valve. All others looked identical to the first set.

Good luck with all that, dj

[AlekStooge]

Turned out nice. Ultra sonic clean then vapor blast. I expressed my concern about the felt seals. I asked about the felt seals, he said they'll dry up? They did. Except the one that was already tarnished, that fell apart. They said not to worry about it and replace it with O-rings or find a source that makes felt seals.



I bent that bracket back in place with MAPP gas. Well it's straighter.

I have to find someone that does plating.

[FourUsTry]

Wow, that looks great.


I gave you links to 2 sources for felt seals above. I don't suggest o-rings on the choke shaft: the experts say it can create too much drag for the choke to operate properly but with some silicone oil on them I think it would probably work. The biggest problem is that the groove is too narrow for typical o-rings of that diameter so you probably have to pry out the retainers and flip them over. You'd probably have to flip the retainers on the throttle shaft for o-rings also -- if I did mine again I might try o-rings there myself in the hopes of a better vacuum seal.


I'm hoping to try to fire mine up this weekend and see if the rebuild fixed my starting problems.

[AlekStooge]

Wow, that looks great.


I gave you links to 2 sources for felt seals above. I don't suggest o-rings on the choke shaft: the experts say it can create too much drag for the choke to operate properly but with some silicone oil on them I think it would probably work. The biggest problem is that the groove is too narrow for typical o-rings of that diameter so you probably have to pry out the retainers and flip them over. You'd probably have to flip the retainers on the throttle shaft for o-rings also -- if I did mine again I might try o-rings there myself in the hopes of a better vacuum seal.


I'm hoping to try to fire mine up this weekend and see if the rebuild fixed my starting problems.

Thanks!

Too much drag on the throttle shaft? I see you've been in contact with Mike Nixon (you did mention it). I'm talking to him right now. I can't find the 4 o-rings on the throttle shaft; on his site. I did find the felt.

You know they are just dust seals right? According to Mike nothing to do with performance or vacuum.

Now I'm looking into plating. Hopefully somewhere local. Also I want to fix one of my float bowl threads. My machinest buddy is going to bring several rethreaders or taps next Friday.

[FourUsTry]

I was saying too much drag on the choke shaft -- the throttle shaft springs seem pretty strong -- but, yes, I got some info from Mike Nixon. He says he has a resource for the "rubber" throttle shaft seals on carbs 2 & 3 but he didn't give that to me (if you find it please share here).


Yes, I get that even the throttle shaft seals aren't really for vacuum but since I'm having lean running issues reducing that (unfiltered) air intrusion doesn't seem like a bad thing even though Honda accounted for that.


I am no expert on carbs so I'm trying to guess at the best approach in the face of conflicting info.


I'd like to hear about the replating and see some pics. I considered trying some DIY zinc plating after doing some successful electrolysis for rust removal, but I wanted to get the carbs done so I can ride this summer.

[AlekStooge]

I stand corrected. You did say choke.

I have the opposite issue. Rich, I hope because if not that means I am chugging oil.

I have a friend that does DIY Zinc but I kinda want some Nickel for aesthetics. I'm looking at some sources. Anyways I ordered the felt seals.

[RAFster122s]

The small tubes in the intake side of the carbs if not totally clear can cause running issues. Carefully check them with some carb cleaner sprayed into those ports, ensure you don't catch it in the face if it is clogged and sprays back out of the tube towards you.  EBadly clogged tube will send everything you spray back out. You should be able to spray into those small ports and nothing kick back unless the spray tube is much smaller than the port.

[AlekStooge]

The small tubes in the intake side of the carbs if not totally clear can cause running issues. Carefully check them with some carb cleaner sprayed into those ports, ensure you don't catch it in the face if it is clogged and sprays back out of the tube towards you.  EBadly clogged tube will send everything you spray back out. You should be able to spray into those small ports and nothing kick back unless the spray tube is much smaller than the port.

This is where my inexperience and ignorance begins to show.

Are these the tubes you're reffering to? I thought these were air jets when people were telling me to adjust (which I don't know how). Where are those then?

Also in regards to vapor blasting. How does it hold up aesthetically?

[Darren Jakal]

Hey Alek,

I just did a quick google search and I see that some one has made a new page about these carbs. Here:

http://www.vintagebikebuilder.com/cb550k-carb-rebuild-demonstration.html

i didn't study it so I can't say how good it is but might be useful. There are threads on this site that go into some detail on these carbs also.

Those tubes are connected to the jets. Now that you have the carb body in your hand you can figure a lot out by looking closely at it. Follow the casting features and see how they had to drill out the body (and then plug some of the holes after) to connect up all the air features. These things really are works of art.

I will look for those other threads and edit them into here.

Take care, Darren

edit to add:

http://forums.sohc4.net/index.php/topic,146893.0.html

This is for PD42A but close enough.

When I did my second set of carbs I found out that they originally had an iridescent finish and I really tried to preserve it on this set.

[AlekStooge]

Read the disassembly portion. All good except:
Philip's screwdriver! That's terrible. The choke screws were easy to remove with a JIS.
Pine sol? No that's terrible it could eat the carb body up.
Choke shaft bushing? I don't see it on my choke shaft nor either the fiche for 77 or 78?

One of my slide screws is bent. I'll have to stop by a specialty fastener place.

So if those lead to the air jets where are the actual air jets and how do you adjust?

Yeah they are little works of art aren't they?

[Darren Jakal]

The jets themselves are in your hand in the previous pictures. The main jet screws into the top of the emulsion tube and that is screwed into the carb body. The other jet (pilot) is pressed into the carb body.

To adjust you 1) buy new jets that have a larger or smaller hole or 2) you drill them out to make them bigger (prolly not recommended).

Lots of pretty good material on the web about carb function.

later, dj

[AlekStooge]

No no no, what I'm asking about is air jets or air screws. I keep hearing people mention those on here but I don't know what they are? Could they mean the IMS or vacuum screws?

Mentioned here by Jerry Griffin
http://forums.sohc4.net/index.php/topic,183361.msg2122865.html#msg2122865

[Darren Jakal]

As far as I know the “air screws” are just another name for the Idle Mixture Screws (IMS). And yes you adjust them by screwing them out from fully seated.

Those brass tubes on the front of the carbs allow air to get back to the pilot jets and the IMSs to make the air/fuel mixture when the piston creates a vacuum on the intake stroke. So these passages need to be clear but there is no adjustment except for the jet hole size and the IMS setting (how many turns out from seated).

Hope this helps, dj

edit:in this picture he calls it the "mixture screw"