I need a carb sync - Anyone in North London?

[michtag]

It'll be interesting to see if there's any improvements by changing the plugs,  but think there's potential circumstances under which that would indicate another error.

Well, there's only one way to find out 😁
Still, it would make sense to have the "correct" resistance all along the line. Some time ago I checked all my coils and leads and changed the caps as a consequence as they seemed to offer too much resistance (and they gave 4 different readings). Did I notice a change? Not really, but I think the problems I have been having are a sum of little "off" things, so I am trying to chip at them all, one by one. It's a process of elimination.
Once I get the timing sorted with a strobe light and the carbs synced I'll see if the idling gets consistent. If not, I'll keep poking around...

[michtag]

Michele, a long shot, but is the petcock gauze clear. I had erratic fuel flow and cleaned it in vinegar and very gentle brush with an old toothbrush. Then a column of water from a tap would pass freely through it uninterrupted.

I find even when all clean, fuel often only manages to flow through one pipe at a time, so eg from empty, carbs 1&2 and 3&4 don’t both get full flow at the same time, and maybe a slight restriction could cause flow to fluctuate.

As I say very much a long shot, but quick and easy to check, and always good to know it’s ok.

Hi Jeremy, that has been one of the many things I have tried in the past. I have a new petcock filter (the one inside the tank), but I must admit I have not opened the petcock as it's not one of those that can be opened via a couple of screws. Petrol flow seems fine and constant though (I have observed while filling a bottle straight from the petcock) and I have a new fuel line, with no kinks and no inline filter.
I have therefore eliminated this as a possible source of my problems.
Cheers
Michele

[JezzaPeach]

Ah ok, different to the 500/4 too.

[paulbaker1954]

Update of the day:
Just before thunderstorms hit (although it's still well sunny here) I decided to have a check at the timing.
-Points gaps were at 0.3mm and 0.35mm, so I made them both 0.3mm now.
-Static timing is spot-on for 1-4 and 2-3

I have tried using my strobe but the idling seems too unstable that I am not sure about anything, so I have not tried to adjust anything. I will try again just to see if I notice it being too far advanced at higher revs, but from first examination it does not look that way. It may be that it advances too soon though. I have tried in the past to use different spring combos in the advance mechanism but never really solved anything, so I reverted to the original setup (I was probably jumping the gun anyway).

Here's a video I shot today, just to give you an idea of what it sounds like when idling. Note that unless you see my hand on the throttle or idle screw, she's doing everything else by herself!

https://youtu.be/ESx_E8mv2vM

Carbs are standard PD46A with. standard jetting, This may not be ideal for the Delkevic 4 into 1 the PO put in, but it should not give problems when idling

As suggested above, I will try spraying carb cleaner on and around the inlet manifolds to check for air leaks there, but I have new manifods and o-rings so I doubt it will be that.

This def sounds like a fuelling issue not an electrical issue. As I said check for air leaks very carefully

[Bryanj]

PD46, just about guarantee the pilot jets or pathways are blocked

[michtag]

PD46, just about guarantee the pilot jets or pathways are blocked

Yes, I've known about the pitfalls of PD46s for a while now....but these have been gone through/into/over so many times that I feel confident they should be fine. Of course I could be wrong so if I find myself at a dead-end I will start from the carbs over again.
I will triple-check for air-leaks as soon as I have the chance
cheers guys, much appreciated!

[michtag]

Small update:

Bike runs fine from cold, for about 2-3 minutes. Then, once warmed up, the erratic idle starts showing. I have (abundantly) sprayed carb cleaner on intake manifolds with no change at all, so for now I tend to exclude an air leak as I could not find any evidence of it (and both rubber intakes and manifold o-rings are new).
I keep on thinking it could be something in the timing (or rather advance mechanism springs, maybe kicking in too soon) and/or unbalanced carbs (only bench synced visually, with a drill bit).

Maybe I'll start playing with the spring combination again, after all I am keeping the original ones as they are and just adding different ones, so anything I do can be undone quite easily.

Cheers

[paulbaker1954]

Small update:

Bike runs fine from cold, for about 2-3 minutes. Then, once warmed up, the erratic idle starts showing. I have (abundantly) sprayed carb cleaner on intake manifolds with no change at all, so for now I tend to exclude an air leak as I could not find any evidence of it (and both rubber intakes and manifold o-rings are new).
I keep on thinking it could be something in the timing (or rather advance mechanism springs, maybe kicking in too soon) and/or unbalanced carbs (only bench synced visually, with a drill bit).

Maybe I'll start playing with the spring combination again, after all I am keeping the original ones as they are and just adding different ones, so anything I do can be undone quite easily.

Cheers

This was exactly the same as mine, I sprayed carb cleaner all over and didn’t show a leak but there must have been one there. I replaced the clips with thin stainless jubilee clips. Word of warning is not to over tighten the clips or there is a danger of the clips splitting the rubber.

I am convinced you have an air leak. One thing you can try is when bike is running get hold of the carbs and pull/push them up and down. Give em a really good waggle around

[michtag]

This was exactly the same as mine, I sprayed carb cleaner all over and didn’t show a leak but there must have been one there. I replaced the clips with thin stainless jubilee clips. Word of warning is not to over tighten the clips or there is a danger of the clips splitting the rubber.

I am convinced you have an air leak. One thing you can try is when bike is running get hold of the carbs and pull/push them up and down. Give em a really good waggle around

OK, that is good info, thank you Paul, I will definitely give it a try. One more question, what do your Jubilee clips look like?
cheers

[michtag]

I have tried to wiggle (vigorously) the carbs when the engine was warm and indeed it did rev up when I pulled the left side up and rev down if I pulled it back down....4-5 times, so there seemed to be a connection there. Other than that it kept on being erratic by itself.
I will definitely have a look at the rubber manifolds and get some new jubilee clips: could I have put them on backwards (front to back)? They seem to be fitting snugly and properly, but hey, I am a novice what do i know? More stuff to re-check....again 

[paulbaker1954]

This was exactly the same as mine, I sprayed carb cleaner all over and didn’t show a leak but there must have been one there. I replaced the clips with thin stainless jubilee clips. Word of warning is not to over tighten the clips or there is a danger of the clips splitting the rubber.

I am convinced you have an air leak. One thing you can try is when bike is running get hold of the carbs and pull/push them up and down. Give em a really good waggle around

OK, that is good info, thank you Paul, I will definitely give it a try. One more question, what do your Jubilee clips look like?
cheers

You need 8mm narrow band stainless ones. I got mine from Inox Fasteners in Southampton

http://www.inoxbolt.co.uk/zen/index.php?main_page=index&cPath=475_498

http://

[michtag]

You need 8mm narrow band stainless ones. I got mine from Inox Fasteners in Southampton

http://www.inoxbolt.co.uk/zen/index.php?main_page=index&cPath=475_498

Thank you Paul, I have ordered mine! Keeping my fingers crossed it will be as simple as that.
Cheers
Michele

[paulbaker1954]

You need 8mm narrow band stainless ones. I got mine from Inox Fasteners in Southampton

http://www.inoxbolt.co.uk/zen/index.php?main_page=index&cPath=475_498

Thank you Paul, I have ordered mine! Keeping my fingers crossed it will be as simple as that.
Cheers
Michele

REMEMBER DONT OVERTIGHTEN THEM IN CASE YOU SPLIT THE RUBBERS

[michtag]

REMEMBER DONT OVERTIGHTEN THEM IN CASE YOU SPLIT THE RUBBERS

I'll be VERY careful

[michtag]

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?