Topic: PD42a rebuild adventure!

[fayettebr]

I’ve had my bike now for 3 months. When I got it the #1 carb leaked out of the overflow if I left the petcock on and the bike was not running. I planned to do a rebuild when winter arrived and I had educated myself a bit, being this is my first bike with  (PD42A) carbs. I’ve read as much as I could find here on these carbs and downloaded  a Honda shop manual and studied it. I got a Keyster rebuild kit and got started.
This is what I found when I disassembled them and a few questions and concerns I have.
I checked the float bowl levels on the bench with clear tubes and supplying gas to the carbs. All looked fine. The carb was very clean, bowls, jets, everything was spotless. I assume it had been apart and at least cleaned just before I got it.

I found no o-rings or washers when I removed the pilot screws. I thought I might flush them out with carb cleaner spray, but I got nothing. I can’t see them inside but wonder if they might be stuck up in there.

My jet needles are shimmed with washers (0.60) which I read is not uncommon since the bike has headers and pods.  I found the springs on the #1 &4 carbs were bent over and not allowing the needle to move freely. I think the 2 screws were not tightened down evenly causing the spring to bind up. The needles appear to be undamaged, but I wonder about the jet  being damaged since the needles were rigid. How are the jets removed?

I don’t know how, but one of my pilot screw tips got bent a little after I took it out. I’m keeping all my parts separate  for each carb in their own container. I guess a throttle valve may have gotten on it.  I know now why the Keyster kit has the tip protected with a piece of tubing.

I going to try not to make anymore stupid mistakes like that one. I want to do a better job on this rebuild than the last guy did.

Oh yea, I also found an o-ring used in place of a retainer clip on the #1 carb  throttle valve link arm pins.

Thanks for any guidance for a rookie.

[mrrch]

Which jet exactly are you trying to remove? The needle jet (tube)?
I've used a small e-clip for the link arm clips (came from one of those cheap Harbour Freight assortment boxes).
Make sure you have the orings & washers on each pilot screw.
PD's are great carbs once dialed in.

[Kong]

On pre-77 carbs that "pilot screw" you are referring to adjusts air leaked into the carb but on 77 and 78 "PD" carbs it adjusts fuel flow in a binary (on/off) fashion.  If its bent you need a new one.  When you put them back in there are both a washer and a very small O-ring that go on it first, along with its tension spring.  By the way, that's one of the ways you can tell it adjusts fuel and not air flow, it has an O-ring on it.

Go back and look inside the screw-hole again looking for your O-ring and washer.  Because the O-ring goes down-hole first what you see is the backside of the thrust washer, which will look just like the bare aluminum of the carb body.  So the thing can be in there but look like its not.  The O-ring and washer will stick up inside the hole and stick well enough that cleaner and air (which you can't get to the backside of them anyway) will not budge them.  If you do not have a set of retrieving picks (you can get a set at Sears for about $5) you might be able to get them out using a hefty sewing needle. 

[Tugboat]

When you say it adjusts in an "on/off" fashion, do you mean that when it's backed out it's "on" and vice-versa when it's all the way in? ...as in, leaner when in, richer when out?

[mrrch]

Correct.

[Kong]

Not only correct but also because it is not a tapered needle (look closely, its got a block step, not a taper) it means that it is either turned on or it is turned off but there is nearly no adjustment capability in-between.

[bollingball]

I have had good luck with a foot ball needle to get those orings and washers out but I snip the ends off so the air comes out the end. If you stick it all the way in the oring and washer will fall down around the needle.

                                          Ken

[cookindaddy]

I used a small copper wire with a hook bent at the end and used that to hook the tiny o-rings and washers out of the holes.

[fayettebr]

Thanks guys I made good progress. I got the o-rings and washers out with a bent wire, thanks cook. The next time I take the link arms off will not be such a pita.  The first time is always the most difficult I guess. It was the needle jet tubes I had concerns about. There were two needles that were installed with the spring in a bind after the po put washers on the needles. This made the needles unable to "float" causing it to possibly rub the side of the jet. My concern was that there might be some damage in the jet. I only bought 1 kit, (1 jet)-- and since I had no visible ware on the 2 effected needles, I decided to take a chance that the jets are OK. I was unsure on how to remove the jet anyway.
I've not gotten in any hurry, I'll work on it bit every day, quit when I get aggravated.

[TwoTired]

Not only correct but also because it is not a tapered needle (look closely, its got a block step, not a taper) it means that it is either turned on or it is turned off but there is nearly no adjustment capability in-between.

This is false.

The pilot adjust needles reach all the way to the carb throat orifice and regulate on a per turns basis with it's tapered tip.   They are different from earlier style carb air bleed pilots, in that they adjust the combined air fuel mixture output from the pilot emulsion tubes rather than just the air being fed to the pilot emulsion tubes.  The taper of the PD pilot needle is wider than the exit orifice hole, making the "step" irrelevant for function unless the carb bodies have been damaged with gorrilla torque.

Further, they are solid tipped in construction, which provides the ability to shut them completely off at full closure.  Whereas, the earlier air bleed screws were hollow tipped and cross drilled, making it impossible to completely shut off the pilot circuit.  As far as I know, only the CB550 F's 069A cabs had solid tipped needles in the air bleed type carbs.  But, they could only shut off the air feed, not the pilot jet flow.  With PD carbs, you can regulate total volume.

You have to look at the carb body as well as the needle itself, as they function together as a unit.

[raymond10078]

I used a thin dowel to remove my "jets, or needle holders".  I recall buying a 1/4 dowel, then trimming down the end.  The "jets" are pushed out from the top to the bottom.  Seem to be a slight interference fit.  Mine came out, and back in with no problem.

[fayettebr]

Thanks kandrtech,
That's what I thought, but I was not willing to risk it. I'll keep my fingers crossed.
TT,
Thanks for the info. I have a good idea of the function of the pilot needle screw now. I just hope I get them adjusted correctly without to much fuss.
I only had 1 of the 4 that needed to be replaced. Got lucky because I only got 1 kit.

I put carbs back on the bike late this afternoon and only had time to fire it up. My bike is a sort of crossbreed. My motor is a '72, kick only. I was glad it fired 2nd kick.