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Messages - keithtraffic
1
« on: September 20, 2021, 07:38:04 PM »
So, I have PD carbs on my 1979 550K3 and they have caused a lot of heartache over the last couple of years, but gave then a long ultrasonic clean (no 2 needed two cleans!) AND replaced all the jets etc AND took great care to set them up properly. With a static balancing the bike seemed to go OK but would not really tick over at anything less than about 1800 revs, but I also went to the trouble of doing a proper balancing job across all 4 carbs with the requisite vacuum gauges - although this resulted in what seemed only very minor changes to the setup, the difference in performance was quite noticeable and the bike also now ticks over evenly at between 1200 and 1400 revs. I am just hoping that after the winter (when the bike wont be used much) I don't find myself back at square 1!
2
« on: August 01, 2020, 09:10:00 PM »
Thanks Ash - this description confirms what I had deduced and found from testing the regulator with an accurate power supply and is definitely different from what is described in the Workshop Manual . The really subtle point is that in Mode 2 the relay armature is in the middle of the two contacts and it is that which selects the higher resistance to the Field coil - this is completely missed in the manual!
But I still can't see the logic, in Mode 3, of the regulator sticking the 10ohm resistor straight across the battery - apart from being rather wasteful the resistor gets incredibly hot as its dissipating nearly 20W - and there's plenty of other load to discharge the battery to bring its voltage back down a bit.
From a purely Engineering standpoint the design does seem rather flaky - simply relying on the regulator armature just sitting in the middle position to optimally regulate the battery charging but I guess its relatively simple and low cost.
Has anyone come up with an electronic version that mimics the regulator operation, giving proper control of the Field current - it seems to be a simple thing to do with a couple of FETs and a dual op-amp and it would be highly accurate!
3
« on: July 30, 2020, 09:27:21 PM »
I have had some charging problems (which I won't go into here) but was reading the Workshop Manual about the charging system and specifically how the regulator works. However, given the circuit diagram I cannot see how it can possibly work as described.
I felt sure I had seem a full description of the operation on the forum somewhere (and it was slightly different to the workshop manual), but despite several searches I can't seem to locate it now.
Does anyone know if there is one and could they point me at it please.
4
« on: July 04, 2020, 05:50:14 PM »
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?
5
« on: June 27, 2020, 05:33:26 PM »
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!)
6
« on: June 15, 2020, 07:04:02 PM »
Thanks - did you replace the plug caps as well - the DSS ones don't come with those?
7
« on: June 14, 2020, 02:41:21 PM »
Thanks for all the help - took the bike out today and generally ok, but did again develop a little chuffing and reluctant No1 after stopping for a while.
I agree tick over at 1800 is definitely too high. I thought the proper figure was about 1000 according to the shop manual?
I have looked at replacement coils and plug caps and they are pretty expensive for original types - over £100 each with VAT for the coils and the plug caps are another £25 each.
David Silver has repro ones at a more palatable £30 + VAT for the coils although they don't seem to be handed (same one for both the left and the right side as far as I can see) - has anyone had experience of these?
8
« on: June 13, 2020, 06:09:50 PM »
Well its all a bit bizarre!
I played around with trying to get the coils off and turning them round but that seemed to be bit difficult in practice and as the no-4 cylinder lead almost reached the no-1 spark plug in any case, I carefully put the coils back in place and fashioned a small 'bare wire' extension, just long enough so it would reach the spark plug from the plug cap, taking care to make sure it could touch any of the cylinder metal work.
But before trying this out I though I would put everything back properly, just to re-check the baseline - and lo and behold the engine fire up and after about a minute was ticking over fairly smoothly - a touch fast at 1600 revs but with no indication of the backfire - and cylinder 1 was definitely working as it got as hot as the others very quickly.
Nevertheless did then swap round the plug leads but this made no difference that I could perceive - so put them back properly again and the engine fired up easily on the starter button with no throttle - and then just sat comfortably at 1600 revs.
So - either disturbing the coils and plug leads has done something or perhaps what ever blockage there might have been in the No1 carb has moved - but I really have no idea which it is!
Assuming the weather here tomorrow is OK I will the bike out again and see how it goes - but any thoughts on the above?
9
« on: June 12, 2020, 07:04:54 PM »
I will give that a go tomorrow - although I am not sure that would explain the situation where I can spray carb cleaner into the vacuum tube screw hole and the cylinder picks up and runs pretty cleanly (for a second or two).
10
« on: June 12, 2020, 05:56:00 PM »
I did think about that but I can't make the No4 lead reach to the No 1 cylinder - is there a quick way round this?
11
« on: June 12, 2020, 04:54:54 PM »
Have now checked the compression after warming up the engine and with the throttle open...
Cylinder 1 165psi
Cylinder 2 155psi
Cylinder 3 165psi
Cylinder 4 160psi
(With the throttle closed all cylinders are the same at roughly 90psi)
So all a fraction low compared to the manual figure of 170psi but I wouldn't have thought the numbers are anything to worry about - and cylinder 1 definitely does not have low compression compared to the rest. I did try squirting in a little oil into the cylinders and that did raise the readings across the board by 20-30 psi.
Another symptom I have just noted is that at tick-over and at speeds up to 2000-3000 revs No1 cylinder is softly backfiring / emitting a sort of sputting sound.
I also tried the trick of blowing into the overflow tube and its definitely clear.
So not sure if this sheds any more light or if really the next stage is to (reluctantly) remove the carbs again and have another close look - is there a diagram or anything of the PD carbs showing all the airways etc and where it should be possible to blow / direct cleaner through to ensure all the fine passageways are definitely clear.
12
« on: June 10, 2020, 08:20:31 PM »
Thanks - I should have access to a compression tester at the weekend so will check that out (as you say it will help to eliminate one possible area of concern).
I did take great trouble to check that the overflows were working and clear before I reassembled the carbs and great care in ensuring that the floats were set to the right height, but will go round the loop again as you suggest just to make doubly sure.
Does using a clear tube connected to the overflow and holding it up to see what level the fuel comes up to give a proper indication of fuel level on the carbs?
13
« on: June 09, 2020, 05:33:42 PM »
Hi All,
Will need to think about the compression tester, but took the bike out yesterday to see how it performed.
Despite previously reporting that things had settled down and I could achieve a smooth tick over, albeit a bit fast, went out to the bike and started it up and again No1 cylinder was not really firing. Nevertheless decided to give it a run to see if things improved.
The throttle response was initially was pretty sluggish until about 3000 to 3500 revs and then things picked up and the bike really accelerated - like a bat out of hell - actually much better than I remember it (which could be the result of the carb rebuild and also getting the timing correct?).
After a good blast it did seem that No1 cylinder was running OK but then I stopped for a while and when restarted No1 cylinder was again not really running properly.
I am getting the feeling that this is still something to do with carburation but as mentioned before I really don't want to take the carbs off again if I can avoid it. So apart from compression is there anything else I can do as a diagnostic before committing to removing the carbs again?
14
« on: June 07, 2020, 07:24:58 PM »
I don't have a compression tester (yet!).
Is there a good one that comes 'recommended' Having watched a couple of videos on this it seems that the 'best ones' have their pressure valve close to the cylinder?
The actron cp7828 which was recommended in the video I saw seems pretty expensive from Amazon - nearly £80!
15
« on: June 05, 2020, 05:56:23 PM »
Thanks everyone for the feedback.
Have been 'playing' a bit today to see what happens. I adjusted the idle screw all the way in and then unscrewed it (as suggested by K2-K6). All the way in and No 1 cylinder pretty much stalled but it did pick up as I unwound it (which I think is as expected). I did find that unwinding it too far also seemed to cause the cylinder to get very erratic. I am not sure if I expected that to happen - is that how its supposed to work? Anyway I returned it to 1.5 turns out.
However things do seem to have 'calmed down a bit and I can get the engine to run with all cylinders seeming to be working - at least they are all getting hot! The tick-over is a bit high - 1800 rmp and the engine still doesn't seem particularly happy at a lower tick-over.
I am inclined to take it out for a run and see how things go.
What are the options for changing the carbs to non PD types - is that a viable option?
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