Carb Balancing

sfcpiet said:
We don't need no fuckin' manuals, we do it all by intuition... :D
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Alfonso Bedoya, Treasure of the Sierra Madre, "Badges? We ain't got no badges. We don't need no badges. I don't have to show you any stinking badges." They don't make movies like that anymore.

Ken
 
I have been chasing a tuning issue on my Pantah for a while.It had a big flat spot just off idle.I tried all the needle positions and after finding the best position it still had this slight lack of punch just off idle,better but still there.So I stated trying mix screw positions and that resulted in it at 2 turns out.I was talking to a mate who tells me he has bought a gadget that digitally measures vacuum,takes some seconds after doing as adjustment to the screw allow this to happen.This gadget is designed for twins,it has 2 ports for the vacuum balancing to happen.The maker was working on a 4 cylinder version but that hasn't happened yet.It has 2 functions,measuring vacuum with one port attached and after pressing a button it then does 2 cylinder balancing by attaching 2 ports.It gets rave review and the maker is having major problems keeping up with the demand.I am going to give it a try and see how it affects where I am on the Pantah.So my question is,does maximum vacuum equal to the best mix screw position.And can this be seen when using Mercury gauges as well as this digital gadget?
This digital gadget is supost to the really acurrate at getting the balance spot on.
 
You could be barking up the wrong tree Vince. Flat spot off idle is more likely to be a mixture problem than a balance problem.
I had the same on my MHR. Seems to be a little lean on the transition from idle. A different slide with less cutaway would probably be the best solution, but opening out the mixture screws half a turn all but eliminated it. It's a bit rich on idle, but who cares?
 
Vince, does it happen as a sensation of momentary loss of power as you accelerate from idle through to speed off from stationary, or is there a constant flat spot if you are sitting with the revs just above idle?

I have the same scenario as the first on the Le Mans. It is due to momentary "flooding"  as the pumper kicks in at low revs. Does not cause a similar problem when accelerating when the revs are already up.
 
Your a canny lot,both of you.Cam the slide idea is one mentioned on another site.Expensive bit of experimentation though.I tried the 1/2 a turn and thats where I am now and its okish.Davo if I give it a fist full its fine,open it at a more sedate pace and it fall flat a bit.I am still going to play with my mates balancer gadget,he payed so its free.Anyone want to weigh in on maximum vacuum happens at idle when the mix screw is at its best spot.Kinda keen to try that on the Laverda when its back on line,I am never to sure the screws are right on muiltipal carbs, .
 
Vince. I've never tried it, but as an experiment you might be able to reduce the slide cutaway with a bit of epoxy putty. If you can get it to stick well enough to the bottom lip of the slide, you could build up the edge and file it back to where you want it (give the slide a good clean with carby cleaner or acetone so the epoxy will stick, and overlap it a bit on the inside for additional adhesion). Maybe add a millimeter or so to the bottom edge of the cutaway. If you find it improves things, then you could go for the more permanent option of new slides.

Cam
 
Laying in bed,cogitation this I had an idea.I already tryed pulling on the choke,as recommenced in the Del manual with minimal effect.So I am going to add a couple of cardboard coffee cups with a few holes in them over the Malossi airfuilters.I have a test spot,its T junction at the bottom of a really steep hill.I will add the restrictors and try a gentle standing start.At the moment it needs a drag race clutch application to work.Like your idea on the slides Cam but this is easier.I am not sure if its rich or lean,time for a test
 
If you have individual pod filters try putting a sock or socks over them. This would give a rough way of slightly reducing air flow, and not let bits of putty get sucked down the inlet tract (potentially).
 
Vince, does it happen as a sensation of momentary loss of power as you accelerate from idle through to speed off from stationary,
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Both my Lavs had/have this, although I never noticed it on my Dell equipped Guzzi 1100Sport.  One of the reasons I went with Mikunis on the 180, and will again once I can scrape together some bunce.
 
When i tried balancing with the carb tune the other day, I was not getting anywhere near the 28 cm/hg vacuum the OP gets in his video at idle. It was wayyyyyy down in the 8-10s if I remember correctly.

Why would this be? I put it together correctly with the dampers etc near the engine.

Operator error of some sort I expect.

Ill have another crack this weekend if the neighbours permit. Its kind of a noisy exercise.
Ed
 
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