I need a carb sync - Anyone in North London?

[paulbaker1954]

Update:

So I have changed the boot clamps to very nice Jubilee clamps and tightened them carefully. They surely hold the rubber manifolds firmer, but I still have the same erratic behaviour, no noticeable change at all. As soon as the engine is warming up (1 or 2 minutes max) idle starts jumping a bit and then spikes to 3k...then down under 1k for no apparent reason. Throttle is responsive and there is no real hang if I blip it.

At this point I feel pretty confident it is not an air leak, so I will be tinkering with the advance mechanism springs, as an old post by Hondaman suggested weak springs (a common occurrence) could cause a similar behaviour.

At this point I would also be curious to swap my (original) coils with good working ones just to rule out they have anything to do with it, but I don't really want to buy new ones right now without the certainty I actually need them...
BTW I have tested mine with a voltmeter and they seem fine, but I wonder if they may start "acting up" once warm?

Having eliminated air leaks then it may we’ll be an issue with the advance mechanism, have you thought of hooking up a strobe timing light I think that would show if the timing was jumping around

[michtag]

Having eliminated air leaks then it may we’ll be an issue with the advance mechanism, have you thought of hooking up a strobe timing light I think that would show if the timing was jumping around

I have thought about it but if the idle revs erratically would that not show the advance mech moving anyway, whatever the reason for the jumping up and down?

One more thing: could the tappet covers o-rings not sealing perfectly cause this? I am asking because I have noticed a little bit of oil just around the rim on 5-6 of them. It's really little, I have to swipe my finger to actually see that there is oil there. Of course, there should not be oil, so I will eventually change them, but i wonder if it could suck in "unmetered air" and if it would end up in the combustion chamber.
Cheers

[Nurse Julie]

Nope.

[michtag]

Nope.

Thanks for confirming; I thought it would be highly unlikely (I guess I would also be burning all of my oil if there was a straight passage to the cylinder) but it's always good to have expert confirmation.
Cheers

[K2-K6]

As julie responded,  through the tappet caps is not possible.

"but i wonder if it could suck in "unmetered air" and if it would end up in the combustion chamber." But via worn, damaged, broken piston rings,  then potentially yes.

The crankcase is vented on most engines via a breather pipe , and usually on these ( I think) into the airbox or out behind the engine.  This is supposed to vent OUT with any oil fumes burnt through the intake to avoid smoke output to environment.

But if the rings are badly compromised it can also suck air in via this route. It would be interesting to investigate this route to see if this is sucking.
You could clamp the pipe to see if the idle speed improves,  or place the end of the pipe into a glass of oil to see if it sucks up the oil while running.

Worth having a look at Julie's 400 rebuild thread to appreciate how bad the rings can be with the bike running quite well.

[michtag]

Thank you K2-K6, just for the sake of elimination I will try that (the breather tube on my bike goes back to the bottom of the airbox) but I really hope it will make no difference!!
cheers

[paulbaker1954]

One thing I would like to add.....

I know how frustrating it can be chasing problems like this, I spent weeks chasing around with an issue that I thought was down to air leaks (but wasn’t in the end). My bike had never idled very well and was always quite and to start despite having rebuilt the carbs and changed the carb brassware.

In the end I got so fed up I bought a set of refurbished carbs from Gerben. Ok they cost 300 but I got 95 back in part ex for my old ones.

Result bike starts first kick, idles like a dream.

Sometimes it just pays to have a professional service the carbs that uses good quality brassware was my take home

Mine is a 500 by the way with 069A carbs not a 550.

[michtag]

One thing I would like to add.....

I know how frustrating it can be chasing problems like this, I spent weeks chasing around with an issue that I thought was down to air leaks (but wasn’t in the end). My bike had never idled very well and was always quite and to start despite having rebuilt the carbs and changed the carb brassware.

In the end I got so fed up I bought a set of refurbished carbs from Gerben. Ok they cost 300 but I got 95 back in part ex for my old ones.

Result bike starts first kick, idles like a dream.

Sometimes it just pays to have a professional service the carbs that uses good quality brassware was my take home

Mine is a 500 by the way with 069A carbs not a 550.

Hi Paul, yes, I have been tempted to go down that route myself, but if I spent that kind of money on my bike (again) I think my wife would show her disappointment by poisoning my coffee or reshaping my head with a blunt instrument.
So I will try to play with the advance springs and see if I can get it to stabilise somewhat enough to proceed with using a strobe light and then syncing properly.
Ideally I would like to try another set of PD carbs before committing to buy a refurbished set, so at least I can have a reasonable certainty that they are the problem.
Cheers

[deltarider]

Listening to that video, does that ultra short high chirping sound, every now and then, not indicate some electric shorting? Or is it just the keys vibrating on the handlebars? I suppose there's no harm in checking if there's any intermittent arcing going on between plugcaps (and/or HT leads) and the head. Best seen in the dark.   

[michtag]

Listening to that video, does that ultra short high chirping sound, every now and then, not indicate some electric shorting? Or is it just the keys vibrating on the handlebars? I suppose there's no harm in checking if there's any intermittent arcing going on between plugcaps (and/or HT leads) and the head. Best seen in the dark.

Hey Deltarider, thank you for your reply and apologies! I have noticed it only now, but I have put all this on the back burner since I was made redundant and completely stopped looking into it :/
Anyway, I had not noticed that chirping sound and it may just be the phone mic picking up or distorting something else (or maybe it's the keys) but I will try again in the dark to see if any sparks appear. having said that, I really doubt it as all plug caps are new....but who knows...coils and leads are still the original ones.
I have also managed to get new return springs for the advance mechanism, so I'll be able to test if those have any impact at all.
Failing all the above, I fear i will have to take the carbs down (again) and get them professionally cleaned to make sure everything is as clean and open as it should be.
many thanks

[JezzaPeach]

Did you ever manage to get the carbs synced using a set of four gauges?
I have a set but I’m in Cobham, Surrey.

[michtag]

Did you ever manage to get the carbs synced using a set of four gauges?
I have a set but I’m in Cobham, Surrey.

Nah... I haven't really even tried yet, but thank you for asking. I actually have my set of gauges, I just needed someone to guide me through the process as I am getting tired of trial and error, despite the tons of good videos available and good posts...
Anyway, with all that's been going on and especially after losing my job, this has gone on the back burner (in fact, the back of the back burner). Last week I tried to check for arcing in the HT leads or plug caps (although these are new), but the battery was dead, so I took it off and charged it.
Then it started raining and I have not been able to manage my time to make it coincide with a dry spell. Then another small DIY emergency had to take precedence, so at the moment I have a charged battery at home and a sleeping Honda under a tarp downstairs...
I need to "pull my finger out" and just take these last steps, but I must admit my motivation is not running very high at the moment...
Like everything, this will pass and I'll get there, but until then I'll just be a bit more grumpy than usual.... :/

[JezzaPeach]

Sure it will pass, and been there more than once. Constantly damp roads don’t help either.
My idle was hanging until I adjusted the carbs.
Just some tips from my limited experience. 
I’d do the carbs first.
I put the tank on the platform of an old step ladder and ran clear plastic hoses to the carb hoses.
My gauges came with little plastic damping screws which they may not all have, but help a lot.
Warm first and don’t use choke with the gauges as mine says it can damage them.
The Honda workshop manual seems to say balance at tickover 1050 rpm or something, which makes sense as that will be at low slide position and give the smoothest tickover. (Like the drill bit tip)

[McCabe-Thiele (Ted)]

Did you ever manage to get the carbs synced using a set of four gauges?
I have a set but I’m in Cobham, Surrey.

My late father used a listening tube to synchronise multiple carburetted engines, he used to great effect on twin SU's & Strombergs on my early cars. I've never tried it with 4 Carbs - sadly my hearing aids are not really up to the job! 

[JezzaPeach]

Amazing skill!