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Black smoke and hanging idle after a full rebuild

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deltarider:

--- Quote from: thomaspigeon on June 21, 2021, 11:01:43 PM ---... I might have some DR8EA plugs kicking around but no R plug caps. @deltarider are you saying that I can run regular caps with R plugs? ...
--- End quote ---
Sure you can. So far I have seen no proof of a positive effect by adding more resistance than the 5kΩ that either a R plug or a resistor cap provides. The discussion pops up every now and then in the international forum, but I have yet to see a falsifiable result, meaning it can be reproduced. In my opinion the plug gap - more or less wide - is far more determining spark duration. 

--- Quote ---... Some people are doing the cam chain tensioning while the engine is running, is that a good idea?...
--- End quote ---
I have to do it like that, as my tensioner bolt is not properly functioning, but I can not recommend it, unless you have to. Do not expect to SEE the bolt turning when the lock nut is loosened. It moves just a fraction! Also do not expect too much result of adjusting the tensioner. Often the culprit is in the ignition or carbs that are not balanced well.
CB500/550 owners are advised to have a look at this video shot by René van Maanen of Honda4.nl. It gives you an idea how the tensioner works and why you will not even see the bolt turn when you loosen the locknut to let it adjust. It will move just a fraction. Also do not expect a wonderful humming engine after adjustment. You will always hear the camchain.
Mind you, the vid does NOT show how to perform the adjustment, it only demonstrates what goes on.To adjust, either do it by the book or like Bryan suggests.
I do NOT recommend to do it with a running engine like Honda's Owner's Manual CB500K3-CB550K3 suggests. I don't know why it is there. Could have been an error in editing by copy and paste.
https://www.youtube.com/watch?v=8qJc6e5pa8M
Courtesy Renë van Maanen - Honda4.nl

thomaspigeon:
Hello everyone,

After countless carbs disassembly and reassembly. I start to see the light at the end of the tunnel.

I'll try to get through the process briefly :

1) I first went for pilot #42, main #98, 3rd clip position
2) Soot and smoke was building up, idle was hanging when up in the revs
3) Changed the spark plugs for DR8EA but it wasn't firing properly and flooding so back to the D7EA
3) Went for new O-ring (thanks Nurse Julie and Fogrider) for the mains and put back OEM needles and emulsion tubes
4) Very little difference but slight improvement in the riding qualty though still soot and black smoke and hanging idle
5) I measured how much petrol were in the bowl, between 50ml and 60ml (is that too much?)
6) I went for pilot #38, main #110 (I don't have any #105), 3rd clip position
7) Somehow some carbs started to leak petrol from the overflow massively and flood the pods (and so the engine)... taken them out to fix this...
7) NO MORE SMOKE! NO MORE HANGING IDLE!  ;D

It really starts to run well BUT it's struggle to take off when hot and sometimes stalls, I really have to rev it to take off. Once rolling it's fine. Basically low revs are bogging. It's idling fine though. If I wait at a red light and try to go it's really boggy like it's building up. I tried to play with the mixing screw but very little difference on this problem. I struggle to put it in Neutral so I guess carburetion is not quite there, yet!

Now here are my different thoughts :
1) Some carbs are still leaking very slightly from the overflow (like a drop or so but only when riding) and I kind of find a bit of petrol under some pods, if the level is too high in the bowl, could it flood the carbs? I don't have any smoke though but I tested late this evening maybe I didn't see it.
2) Clip position is too high so it's running too rich when accelerating
3) I need to go for #40 pilot jet
4) Get the DR8EA back on to see if it helps to fix this

Let me know what your thoughts are on this one,
Thanks

Tom

fogrider:
Tom, I had confusing symptoms on mine, it always seemed really weak just off idle, gasping/bogging, but never any black smoke.  I finally found the idle circuit was over-feeding the full range, even though it ticked over OK. Idle jets measured as 41.
Long story short, it needed SMALLER idle jets, contrary to the symptoms. 35's have cured it , completely. Got 'em in a cheap aftermarket kit for a CB350.
It seems  illogical, but it worked (for me anyway).

I think it was the American side of these forums where I read two owners with EXACTLY the same issues. After trying everything, it looked like they finally gave up and flogged their bikes, I reckon the illogical step of smaller idles would have made them happy owners too.

Good to see you don't give up easily.

Trigger:
I have found over the years it is very hard to advise on carbs as, they all have different worn out parts. And all have different engine's in different states. You can be chasing a carb problem for years if one head valve is leaking  ;)

fogrider:
Quite right, the older the bike, the greater the mileage done, messed with by previous owners etc, plus going by previous experience can be misleading too. Until I put the Lambda sensor in I was convinced there was weakness causing the problem , the symptoms seemed pretty clear, I wasted a lot of time trying to resolve weakness.

The Lambda showed the reality, or I would be still chasing it now !

She was badly neglected so lots of things to resolve all at once which did'nt help.

Keep at it Tom, it's all part of the fun......

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