Ide troubles with pd50 carbs

[Bongskit]

that's alright. so you will have more time to clean and recheck, and clean and recheck it more like what I did. carb that old and a pain to get in and out of the bike, should be done at least to a minimum if not, once. it took to me awhile to find 1 idle screw. I had to visit this old but trusted mechanic back at my hometown to get it. maybe this week I will have it all put back on the bike.

[my79650]

Got #4 left to clean; as long as you can see light thru those damn holes; you should be good to go. Yes they are an annoying part to install and remove. I have to stick my hand in the airbox so i can get the rubbers mounted on that side.

[my79650]

Reassembly is on hold for now; need to pickup JB Weld and silver solder; better to block off the air diaphram passages as 2 of them are not in the best shape. I scratched up my slow jets pulling them out with vise grips, tried the cloth idea on them but my wrench kept slipping off. I didn't go crazy with the pressure on them for removal; used emery cloth to smooth the burrs up. Camera is down or i would have had pictures. Float level was off on all 4 at least 1/4 inch. I measured them up with a tape. As long as you have everything sitting level on the bench this works as well. I also added a few drops of oil to the jets and any o rings to freshen everything up and to keep them clear til i do a leak test. Oil will wash out and freshen up any passages and rings. I didn't bother wasting my time dipping my carb rack.

[my79650]

got some photos of crappy cutoff valves and solder; i used silver solder for metal; was touch and go for awhile but i managed to get them; the trick is to fill the hole with lots of flux then apply heat.

[my79650]

Air cutoff valves; when they are working you can't complain. 2 were going bad so i sealed up the whole lot. As for the actual cleaning process; it went well. Wasn't as bad as i thought. Anyhow when i screw them to the mount plate; they bind up; back off the screws and they work properly at the throttle mechanism, snap right back, when tight i need to use pliers to close and open. Nothing looks bent to the eye but....any ideas?

[my79650]

Found the problem; choke rods are bent; i assembled them without those in place(no working choke for a few years) and they lined up with the front main plate; no binding of the throttle at all now. Going to try to get them straightened out to keep those holes filled.

[my79650]

After another hour i got everything lined up; on the bike now. It seem like my air box rubber are a little short, Can get the outside ones on with a little effort. My problem is the inners now. They barely reach, so i got an old radiator hose that's a little bigger round than the originals. I am going to split them and wrap them around both the rubbers and carb throats on that side, clamp and add a little sealer then it should be fine as the isolators on the head carry all the weight.

[Volker_P]

Possibly a misalignment problem?
The airbox rubbers may be turned in the plastic distibutor part to align with the carbs. There are marks that basically should point to the inside.

[my79650]

I had the airbox off and lined up the dots; still not any good; 33 year old rubber was starting to crack and shrink; didn't matter that i pushed the air box up to nearly falling off they still wouldn't reach. I took an old boot into the auto parts store and sized up a radiator hose. Cut to length and with a little bit of wd-40 and elbow grease they slid into the original holes on the airbox. be generous with lubricant to slide them from the air box to the carbs; use a small flat screwdriver and stick your hand into the air box to slide them up to clamp them down. Got to order a new accelerator pump diaphram; toasted after 33 yrs, might be original.

[my79650]

Will order new diaphram today; will add more pictures after i re-install the carburetors. I set the idle screws to the 1 5/8 turns as the cosky manual said to; just held up for accelerator pump.

[my79650]

Over 2 weeks and still waiting on a acc. pump! Why did they make that in these? Emission laws at that time? Next question: has anyone ever tried to block off the accelerator pump and still have functioning set of pd50 carbs?

[my79650]

Finally the acc. pump showed up. Ordered for a set of 78 750 pd carburetors. Don't know the exact carb number but the pump is the same including the length of the push rod on the plunger. Another note is the one i got does not have the little o ring so save yours if you can. Will post pictures later today.

[my79650]

Camera down again; but the bike runs, and it idles now at 1200. Even after a few minutes of warming up. blocking off those air cutoffs solved my idling issue. Set the air screw to 1 5/8 turns like factory, idles a little rough but as long as it don't quit every time i stop or let off the throttle it will do.

[my79650]

Now it acts like it has a flat spot when when driving round 50km/h in 4th round town. On the road in 5th when its pulling it seem to perform fine. Would readjusting the air mix screws clear this up? Set them to factory specs after cleaning.

[Volker_P]

Idle screws is only fine tuning for idle.
Rather a synchronization or an accelerator pump issue.
Or maybe weak ignition.
One may also check what happens without the air filter cover.