Ongoing PD46 carburettor woes (possibly)

[JezzaPeach]

Actually just checked a despite the pic 2&3 are well clear, but the long straight ones were the original format (?) so good to keep original look (apart from the pressed metal caps maybe!)

[keithtraffic]

Hi All,

So......

I have replaced the coils (with aftermarket ones for DS) as well as the plug caps (just for good measure as the ones fitted actually look pretty good) and unfortunately things have not improved - same poor low revs performance from cylinder 1 and the slight 'sputting' backfire ae low revs is still noticeable.

It's looking like I am going to have to remove the carbs again to make absolutely sure everything is totally clear and clean - but does anyone have any final last thoughts where else to look before I do down this route - it seems most other things have been tried!

Also does anyone have a decent rubber connector between Carb 1 and the air box - I have noticed mine is beginning to split and an not sure it will survive another carb change (but its not the source of any problems as I have made sure its not leaking when testing the tickover!)

[Bryanj]

I think that is the especially unique one due to length and shape, it was discussed on the forum elswhere about a member on US site hand making them

[OZZYSBIKES]

Re the carb to inlet box rubbers, I managed to get in touch via the us forum and email with the man who is manufacturing replacements, he is very helpful, I got mine delivered in about a week and less than $50 including postage, I'll get his email when I finish work,

PS I am having very similar problems with my bike, I am about to clean the pilot jets for the fourth time which does get the bike running ok for a while, I am on the lookout for a set of alternative carbs as these PD carbs seem prone to issues (odd as they are not particularly complex carbs)

[Bryanj]

Problem was then were designed to run as lean as possible for california so any blockage at all makes them impossible

[OZZYSBIKES]

Let me know if or when they are for sale, if I can have first refusal it will be appreciated

[OZZYSBIKES]

The email address for Paul Gabor is mybluebike2004@yahoo.com

He responds quickly and is a pleasure to deal with, the rubbers that you will receive are not quite as good looking as genuine ones but not noticeable when fitted, not much choice anyway, the ones from Germany on Ebay are twice the cost and I believe are from Paul

[Bryanj]

Ken i will go seconds on the carbs as i dont think i have enough for the engines/frames i have

[Bryanj]

I will be honest and say i dont know for certain exactly how many frame/engine combos i have and what bits i am missing

[keithtraffic]

So, finally bit the bullet and removed the carbs yet again and went through the cleaning process (again) on carb 1, making absolutely sure that that the pilot jet and the passage ways serving it and the mixture screw were definitely clear.

good news! Having now reassembled everything the bike started with the smallest blip on the starter and after a minute or so to warm up was ticking over smoothly, albeit still a little high at 1400 - 1600 revs. But most importantly cylinder 1 was working properly!

I will take the bike out for a run in the next few days to see if everything else is OK, but I guess I still need to set up the idle adjustment properly (at the moment all four screws are just out by 1 1/2 turns).

I am sure I have seen some guidance on the forum for how to do that properly but can't find it now - does anyone have a link to the relevant thread?

[Bryanj]

Use it regularly or those carbs will be off again

[deltarider]

... albeit still a little high at 1400 - 1600 revs... but I guess I still need to set up the idle adjustment properly ...

Verify the RPM with a true tacho. I once worked on a K3 and couldn't achieve a nice idle. Then I connected my automotive DMM. Guess what... a true 1000 RPM showed 1400 on the ND tacho. No wonder that when I tried to dial the RPM down to a 1000 on the onboard tacho, it didn't run well. Not saying it is also with yours, but I'd check it.

[JezzaPeach]

That’s very interesting about tacho accuracy, it would explain a lot. 
PS re jet etc cleaning I found these pretty good, and used a mini bit holder in situ on the bowls, with some contorting (mini rachet on order)

[Bryanj]

Carefull with the wire thingies the pilot jets have a sort of cast in spider for some reason, maybe to atomise better?

[K2-K6]

"I am sure I have seen some guidance on the forum for how to do that properly but can't find it now - does anyone have a link to the relevant thread?"

From a Honda manual,  set the adjustment screws at recommendation for turns,  warm bike to stable tickover off choke, then turn screw on one carb anti clock* and observe engine revs rise (this is where the accurate tachometer comes in) you should reach a peak revs after which the combustion will start to get worse if you keep going. Turn screw back to "peak" revs and then keep going until you see a 100rpm drop ( because you've made it richer) and that's the final calibrated position for that carburettor and jet.  ie. You are getting it set to juuust slightly rich of the leanest burn position.

Now adjust the overall tickover with the manual single screw if the revs are too low or high,  then work individually through the remaining carbs one at a time.

This routine gives ultimate parity of tick over setup as you'll have just created the same combustion level bespoke to each single cylinder and it's associated carb.  The number of turns out should now be recorded as a baseline setup for your bike.

* some carbs are opposite depending if the idle mixture screw is located on engine side of throttle slide or airbox side.