Carb Balancing

[RED BARON]

I want to check and adjust the Carb Balancing on my 1990se. Dellorto DHLA 45M As I have noticed that since the MOT last week, the CO and HC figures have risen some since the one last year. Also the Exhaust looks very Sooted up and I seem to be using a lot of Petrol now.
The figures for last year 2023 are :-
CO 0.480 HC 630
The figures for this year 2024 are :-
CO 1.120 HC 716

I will be checking the CO reading before and after just to see the difference.

I have bought a 4 Carb Vacuum Synchronizer Balancer set complete with the 4 Brass Tubes and Rubber Tubing.
But it didn't come with any Instructions on how to fit and use them.
All the information I have found and Video's talk for a 4 Cylinder Motor Bike.

Is there any Videos that would help to make it a little clearer, how to set up and do the adjustment on the Dellorto's?
I do have some Written Instruction but isn't clear as to if you have to take out the 4 small Vacuum Hole parts and replace them with the 4 Brass Tubes supplied, then put the Rubber Tubes from the Gauges onto them.

[John]

I got one a few years back from Eurocarb, the Dellorto parts supplier. You're right, you have to remove the vacuum port plugs, then fit the threaded brass tubes so you can connect the rubber pipes. I balanced a length of timber from the roof to the bonnet and hanged the device from that so I could see it while adjusting the carbs. It made a difference to how mine ran, better pick up and steadier, less lumpy idle.

Before balancing I made sure the throttles were synchronized - the throttle cable arm has an adjuster on it, worth checking before doing the vacuum gauge job. I also checked the timing with a strobe before looking at the carbs.

Good luck

John

[RED BARON]

Thanks John.
That does make it a little clearer. That I do have to use all four of the Brass Tubes.
I have now checked the Throttle Linkage between the two, and they both move together. So that bit is ok.
I will be checking the Timing as well.
Also the CO reading before and after, just to see if it has come down.
That is a good idea to mount the Gauges and hang them down to make it easier to read them, also keeps the Rubber Tubes clear.
I think I will do the other one as well if this one is a success later in the Summer.

[John]

Hope it makes a difference. One other thing, if you find that you can't get all 4 reading the same no matter how much you adjust them, there may be a vacuum leak. Most likely a split vacuum hose or the carb to inlet manifold.

Cheers

John

[Alan_M]

Tim Engel (Esprit2) has written a very good guide to balancing carbs.
It’s in the files section of our Facebook group
- https://m.facebook.com/groups/174212968 ... 586587390/

Also, you should find it on here with a quick search.

[Esprit2]

Thanks, Alan. I was trying to figure out how to post it here. Apparently I can't, so that link you posted is very helpful. This shorter link will get you to the same place...
https://tinyurl.com/3esmdx53

The "Files" section over on that Facebook Group has great potential as a "How To" library, but I think it's under-utilized... at the moment, there are only seven files uploaded by two people. I encourage everyone to copy-paste their best, most helpful messages into a Word/ Excel/ PDF/ JPG file, and upload it over there. It might help someone else later on.

Also, I encourage everyone to go browse over there. Download any files you want for one price... "free".

Regards,
Tim Engel

[Tanz]

Some pictures that might be helpful ?







Some of these things labeled above have different names in various books just to confuse me which isn't difficult!

[RED BARON]

I would just like to say thank you all. Also the pictures were also helpful on how to connect the Gauges.

[MetBlue]

Great timing to this thread and thanks to Tim for great document on How to. I'd been wondering about ports on the later F pipes carbs, but was answered by Tim. Unplug the F pipes.

I've been playing today with 4 vacuum gauges from back in my motorcycling days. I'm balanced across pots using the bypass adjustment, but turning the idle mixture doesn't seem to affect the engine speed or vacuum level. Maybe the vac level is because a gauge has less resolution than a manometer? But doesn't explain the revs. What amount of change in revs could be expected ?

Tony