Needing Air

Rohan said:

Jim Mosher is the engine guru on other lists.
http://www.performanceindian.com/VinAmalMods.html

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"the motor is getting enough air, but not enough fuel at slight slide openings, causing a lean mixture, and detonation. This can be cured by cutting the entire back half of the nozzle away behind the needle. Now the air entering the cut-away opening in the slide doesn't have to rise, and go above the nozzle, it can go around the sides of the nozzle, and the resulting vacuum will pull fuel up, and around the needle at lower slide openings. I noticed that the factory did this on the Concentrics on my '75 Norton 850 Mk3. " (Quote )

He noticed ...
All about small throttle openings .. not a word about 4 ring ( leaner ) needle ..relation with exhaust or air filter restrictions ..
If he is your 'tuning guru ' , then I am Einstein ( and confused ..)

Some years ago , I tried to find out what the effect of different types of spray tubes would be on the signal strength ( playing wouldbe Bernouilli , so to speak ..) in concentric amals .
Using 6 diff. carb bodies , shop vacuum cleaner , 1m water column on a modified main jet , micrometers .. taking great care to eliminate all other variables : allways the same slide , needle and jets , blocked choke and pilot circuits ..
While a 0.1 mm change in slide position had a significant effect on the water column , I could not detect a difference within the spray tubes.
I exchanged a few mails with John Healey , who did similar tests , which where equally inconclusive .
It is a pity I no longer have his mails ( gone with an old laptop ) .
What I do know , and is easy for everyone to mesure , is that the 4 ring needle is leaner at larger throttle openings .
So , the big question remains ( at least for me ) , what caused that huge flat spot that Rowley said he discovered , and that was magically cured by cutting a simple step in the spray tube and reducing main jet size ?.
The 'expert opions ' regarding the cut spray tube seem to be equally divided between too rich or too lean .
Some say it was to meet EPA regs , others say it was to cure leanness at small throttle openings . None of them refers to Rowley .
It shouldn't be too hard to mimic Rowley's roll on test ? .
In my 850 engines I have slanted spray tubes , 2 stroke , or rather Triumph style .
Why , I don't really know . Intuition maybe ? .
But then , I do other strange things ..

Hi ludwig.
I was planning something similar but struggled with replicating the one-in-four stroke pulse at low revs using a vacuum cleaner. Can you elaborate on your "...While a 0.1 mm change in slide position had a significant effect on the water column , I could not detect a difference within the spray tubes..." as I am not sure how your apparatus and instruments were connected from your description.
Ta.
I suspect you are already being quoted on other forums as 'I recall speaking to a guru who told me about an experiment... blah blah blah'.

A couple of years ago, I did a little experiment, which I never followed up or refined.

I cut the tops of the needle jets short, in a twin 928 setup on a Tri. 650. Took about half of the parallel portion off.

Anyone want to try guessing (or even knowledgeably stating) what the main noticeable effect was?

Sorry about the Triumph reference, but it's in a Norton frame haha.

Triton Thrasher said:

A couple of years ago, I did a little experiment, which I never followed up or refined.

I cut the tops of the needle jets short, in a twin 928 setup on a Tri. 650. Took about half of the parallel portion off.

Anyone want to try guessing (or even knowledgeably stating) what the main noticeable effect was?

Sorry about the Triumph reference, but it's in a Norton frame haha.

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Hi Triton Trasher.
Maybe: Nothing, the fuel climbs the needle.
Ta.

needing said:

Can you elaborate on your "...While a 0.1 mm change in slide position had a significant effect on the water column , I could not detect a difference within the spray tubes..." as I am not sure how your apparatus and instruments were connected from your description.

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The setup was something like this :



The cristal tube hanging in a bowl of water , 1 meter lower .
Compensation holes taped up , air mix screw fully in . choke hole in slide taped , slide greased to prevent air passing (Amal slides are designed with a specific clearance in the body ) 2nd slide on top to make sure it stayed down .
Always same slide and jet holder . Only the bodies ( 6 ) with different spray tubes where changed .
With the idle stop screw I could raise or lower the slide(s) , always starting from exactly the same height .
The std stop screw allows the slide to rise well above the spray tube .
The water column would rise to a certain point and then fall back .
I marked max level and intermedeate levels .

I am fully aware that this test is not a true representation of what happens with the carbs installed on an engine , but I only wanted to see if there was any truth in those stories of airflow over , around , behind ... the stepped /slanted / straight .. tubes sucking up more or less fuel .
I did not see it . Maybe my setup was too primitive , or am I too stupid ? .

needing said:

Triton Thrasher said:

A couple of years ago, I did a little experiment, which I never followed up or refined.

I cut the tops of the needle jets short, in a twin 928 setup on a Tri. 650. Took about half of the parallel portion off.

Anyone want to try guessing (or even knowledgeably stating) what the main noticeable effect was?

Sorry about the Triumph reference, but it's in a Norton frame haha.

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Hi Triton Trasher.
Maybe: Nothing, the fuel climbs the needle.
Ta.

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Good, intelligent answer, but no, it did have an effect.

Rohan said:

Dunno, I've never explored precisely how they work - they just work, very well.
.

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Every morning , a guy sees his neigbour strawing some powder on his lawn .
One day , he walks up to his neighbour and asks :
" Why are you strawing that powder on your lawn ? "
Neigbour : " It keeps the elefants off the grass "
Guy : " but ..but there are no elefants around here ..! "
Neigbour : " ..see how well it works ..? ! "


( sorry , couldn't resist .. )

Hi ludwig.
My first thought was to improve the discrimination of the gauge by using a much smaller ID clear tube. I'll look closer in the morning.
Hi Triton Thrasher.
I'll wait to hear now 'cos that was my best shot.
Ta.

Might as well tell you now.

I doubt that many people care!

The noticeable effect was a loss of all power for a long moment, when you opened the throttle from road cruising speed, as you do when you go to overtake another vehicle.

It showed me that Amal's tube full of froth to do the job of an accelerator pump does work.

Do these new Amal Premiers have the cut away spray tube ?

If the Vincent guys are cutting their spray tubes for better performance,
maybe powdering the grass does keep the elephants away !

Triton Thrasher said:

Might as well tell you now.

I doubt that many people care!

The noticeable effect was a loss of all power for a long moment, when you opened the throttle from road cruising speed, as you do when you go to overtake another vehicle.

It showed me that Amal's tube full of froth to do the job of an accelerator pump does work.

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Thanks Triton Thrasher.
I gather cruising function was not noticeably affected, just the transition from one throttle opening to next if rolled on too quickly i.e. a loss of fuel draw response to throttle opening change. BTW There is currently no 'pump' onboard a Mk1: it functions entirely on Venturi airflow and Bernoulli effect. A pump would have to be able to force fuel even with the engine off: then you could do away with the ticklers to flood fuel down the throat! Hobot spoke of a concept for an apparatus on the main jet to pump fuel (or that was my interpretation).
Ta.

The Amal blurb talks of a tube of fuel/froth available for enriching duties if the throttle is opened suddenly,
which is what triton is speaking of... (?).
Does the same job as an accelerator pump.

If one could direct a puff of mild pressure into the float bowl area that would spritz fuel out into air path regardless if throttle opened or not. I am a blur on details to implement, maybe just an air bulb you could squeeze as much as the mood struck - or not. I can think of a lot more complex ways to dial in proportional doses. Almost everything starts easier with some wet gas down carb throat.

Rohan said:

The Amal blurb talks of a tube of fuel/froth available for enriching duties if the throttle is opened suddenly,
which is what triton is speaking of... (?).
Does the same job as an accelerator pump. [What a load of rubbish!]

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Dear Rohan (and the "We" in there).
Your current on-dit creates even more semantic satiation for readers but I suspect that may be your intention.
Simply put, repeating your same AMAL nonsense decade upon decade does not create reality for the discerning: listeners just stop registering the drivel until even repeating, LOUDLY, S.L.O.W.L.Y. and ad nauseam, it falls on their now deaf ears.
Real world Reality 1: Mk 1's do not have anything that resembles or functions as an accelerator pump, and
Real world Reality 2: Fuel 'froth' collapses the moment the throttle slide is closed.
As you clearly have not intended to understand, the topic currently being discussed is about how quickly the fuel column ('froth', to you) through the jets can be restored when the throttle slide is re-opened.
Please desist your on-dit and even more positively, start your own (there's a thought) thread to expound your reality as you perceive it from the 1960's.
Ta. Goodbye.

hobot said:

If one could direct a puff of mild pressure into the float bowl area that would spritz fuel out into air path regardless if throttle opened or not. I am a blur on details to implement, maybe just an air bulb you could squeeze as much as the mood struck - or not. I can think of a lot more complex ways to dial in proportional doses. Almost everything starts easier with some wet gas down carb throat.

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Hi hobot.
Where would be an appropriate location for the bulb to be clenched that would not be positively reinforced with a positive increase in speed via rapid acceleration?
Seriously, replacing the ticklers with a one-way valve to pressurise the otherwise sealed float bowl may be a avenue to explore. Good stuff.
Ta.

needing said:

Simply put, repeating your same AMAL nonsense decade upon decade does not create reality for the discerning: listeners just stop registering the drivel until even repeating,

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Thats what the Amal blurb says.
Tritonthrasher would seem to have picked it up somewhere along the line too.
If there is no capability to enrich the mixture for acceleration, not much acceleration will happen. !
Ask me how I know - having experimented with such things - not on Nortons though.

If you don't like it, or can't be bothered reading up on it, so be it.
Making up your own version of pseudo science or physics helps no-one here...

I have not thot this through but wondered about a small balder on twist grip that would only work for one squeeze at a time and take a short interval to reinflate. A mean grip&twist for feul shot or just twist w/o the mean grip for normal. Might take some skill to refine the effect manually. I would tap into the tickler ports. I thot about knee squeeze but a quick bike makes you reflex lock down an instant before throttle snaps so scratch that. I may have to add a float bowl feed with air pressure solenoid to add feul to Drouin injector if NOS added.

An electrically operated switch at the end of twist grip travel to operate a solenoid give it a shot of fuel - and a little leccy fuel pump to supply the pressure.
Sort of a proto fuel injection nozzle, with no intelligence...

Of course, you could cut away the spray tube to do it the Amal way....
850s come with this standard.
Too uncomplicated for Owen, we guess....

someone is over quesstimating how much fuel needed for accelerator pump as can only richen up so much with low air flow till rpm air flow pulls all the feul it instantly needs. For Peel more gizmos needed to add feul over a longer interval of dry NOS into Drouin ~ doubling its mixture delivery if I even dare. To get much pay back form accelerator pump reponse fill in implies one can afford new rear tires more often.