DIR Return Create A Forum - Home
---------------------------------------------------------
The Mighty Nuovo Falcone VOC
HTML https://nuovofalcone.createaforum.com
---------------------------------------------------------
*****************************************************
DIR Return to: Engine and Transmission
*****************************************************
#Post#: 1056--------------------------------------------------
Carburettors
By: Falconefan Date: October 1, 2015, 1:20 pm
---------------------------------------------------------
Hi Everyone,
Just in case you don't visit the other place, here is a
duplicate post of mine:
Well, I’ve been doing some research into carburettors fitted
to the NF’s and have found some interesting snippets (I must
have too much free time!) particularly involving the differences
between the Civilian and Military models.
I came across a web site
(
HTML http://www.thisoldtractor.com/topics.html
) which has various
Guzzi handbooks for both models and in several editions, and
also Dell ‘Orto data.
Both models use Dell ‘Orto 29mm carburettors with 265
Atomizer and 80 cold start jets.
The Military model has a VHB (A) carb, with a #60 slide, a
132 main jet, a 50 idle jet, and a V10 needle.
The Civilian model has a VHB (CD) carb, with a #50 slide, a
122 main jet, a 55 idle jet and a V5 needle.
So, what are the differences? The main one seems to be that
the VHB (CD) carb has a piston type accelerator pump, the VHB
(A) does not.
Comparing the two carburettors up to about a quarter
throttle, although the Military carb has effectively a larger
opening because the V10 needle is slightly smaller in diameter,
the #60 slide has more cut-up which will result in a lower
vacuum and so draw in less fuel. In the case of the Civilian
bike, although the needle is slightly larger in diameter and so
restricts the atomizer jet more, the idle jet is also larger,
and as the #50 slide has less cut-up, the increased vacuum will
suck through more fuel. I am inclined to think that one set-up
balances pretty evenly with the other at these small throttle
openings.
As the throttle is opened up between a quarter and three
quarters, the tapered needle takes over the fuel metering. The
V10 needle has a shorter taper than the V5 and at both extremes,
the figures imply that the Civilian bike runs slightly leaner
than the Military at constant speed. The Civilian will get
enrichment during the actual turning of the twist grip because
of the accelerator pump.
Above three quarters opening the main jet is responsible,
again the Civilian running leaner than the Military.
It could be that as the Military bike would generally be
used on slow patrol and escort work with a restricted flow of
cooling air, it was decided to run it with a richer mixture to
avoid over heating, while the Civilian model could run leaner as
it would generally be out on the open road. In this case the
pumper carb would also be an advantage.
So, why the interest and calculating? Well, as some of you
know, when I bought my Military NF, it came fitted with a 30mm
VHB(CD) carb. The throttle slide cut-away (a #40) implies that
it came off a Sparda. Following suggestions given in a printed
download that came with the bike, the carb had been fitted with
a 55 idle jet and although the suggestion was for a 140 main jet
it was actually fitted with a huge 145; the print-out having
been amended in pencil. There was no reasoning given for these
recommendations – they were just stated as starting points for
experimentation. The standard jets for the Sparda is a 125 main,
a 50 idle and a V9 needle, together with a 265 atomiser, one
carb filling a 500cc cylinder. Bearing in mind the low cut-up of
the slide, the 50 idle jet should be perfectly good.
Where to now? I did 250 miles last weekend going to the
MGCGB AGM, and was slightly disappointed that getting above
60mph was pretty impossible, even though it was delightful
pottering along at 45 to 55. I think I will take the original
carb off to inspect it, clean it and check wear on the atomiser
and needle. If I need to order new parts I will also get a
couple of new jets for the 30mm carb and do some experimentation
with that, particularly as I intend to use it on the open road
rather than patrol work! I don't think the extra millimetre will
make much difference!
Just as an aside, in all the manuals I have recently seen
the tappet clearances have been given as 0.1 and 0.2mm rather
than 0.05 and 0.1. Perhaps the experience of valve burning
prompted the change?
Best wishes,
Susie
#Post#: 1058--------------------------------------------------
Re: Carburettors
By: cloggy Date: October 2, 2015, 6:44 am
---------------------------------------------------------
The tappet clearances open up as the engine warms. The only
specialist dealer I know sets them up no clearance cold. As I
can't get to both pushrods to check if they are rotating I just
set them up with smallest amount of play I could feel
#Post#: 1059--------------------------------------------------
Re: Carburettors
By: huub Date: October 2, 2015, 11:54 am
---------------------------------------------------------
[quote]The tappet clearances open up as the engine warms. The
only specialist dealer I know sets them up no clearance cold. As
I can't get to both pushrods to check if they are rotating I
just set them up with smallest amount of play I could
feel[/quote]
try kickstarting your NF after a fast highway run , you will
find it has hardly any compression left
the tappet clearances actually close when the engine heats up.
i have seen enough burned exhaust valves , i keep my valves at
the lose end .
#Post#: 1060--------------------------------------------------
Re: Carburettors
By: Kater Date: October 2, 2015, 3:33 pm
---------------------------------------------------------
The 0,2 and 0,1 mm are for the cold engine! Huub is right, it's
better to be on the loose side.
A lot of "so called specialists" like to have a silent engine
and burn down the valves, absolutely crazy.
Kater
#Post#: 1064--------------------------------------------------
Re: Carburettors
By: banquo Date: October 3, 2015, 7:51 am
---------------------------------------------------------
Back to the OP, is it not correct that the Civile has a lighter
flywheel than the Militare?
My seat of the pants take on this is in terms of engine
responsiveness.
I have a pumper carb. and loaned it to another local Militare
owner, who found no benefit.
My belief, simple and naive perhaps, is that there is no point
in having a pumper on a motor with such huge inertia.
If you throw a whole lot of fuel in there, and the engine cannot
respond fast enough to accept it, it will do no good at all.
If (any my memory isn't as good as it once was) the Civile has a
smaller rotating mass, then possibly it can benefit in terms of
responsiveness from a pump?
Surprisingly, the NF engine does seem to be very sensistive to
exhaust back pressure too, and it will choke up at the top end
if the gases don't flow freely. With the original double dcker
fitted, mine would happily run at 70 mph on the flat, with a
fully baffled pipe, it choked up at 50 mph, and with the current
pipe, a stock Harley pipe with a square point chisel through the
baffles, it's a bit weak at the top end.
Fitting a pattern (not K&N) air filter resulted in it not
wanting to run much above 1/4 throttle, which was a surprise.
I must spend some ime messing about with main jets to see what
happens, but life's too short...
#Post#: 1067--------------------------------------------------
Re: Carburettors
By: Kater Date: October 3, 2015, 12:49 pm
---------------------------------------------------------
It's a fairy tale that the Civile has a lighterflywheel! The
advantage of the pump is that you get a more fat mixture when
you accelerate, I proved it with a lambda sonde. I use it for
adjusting the carburettors, the crazy fact is that each of my
engines need different needles and jets with the same type of
carburettor. But I have to say that both are modified, bigger
bore, an other camshaft and so on. I have an original NF
military and this one don't won't to go faster the 60 mph too.
The original air filter of the NF works better than the most
modifications, that's a fact my late friend and falcone
specialist George me told.
#Post#: 1068--------------------------------------------------
Re: Carburettors
By: banquo Date: October 3, 2015, 1:32 pm
---------------------------------------------------------
;D Told you my memory wasn't much good Kater!
Thanks for correcting the myth!
Actually, it does make sense, because opening the throttle too
quickly on the Militare causes spoit back through the
carburettor, presumably caused by weakness, that the pump would
overcome...?
#Post#: 1070--------------------------------------------------
Re: Carburettors
By: Nitram Date: October 4, 2015, 3:56 pm
---------------------------------------------------------
I've been interested in the subject of accelerator pumps on
carbys since I first came across the Dell-Orto pumpers fitted to
my 860 Ducati.
Why is it that they are there at all ? Obviously it squirts a
stiff dose of pure fuel as the slide opens, grossly enrichening
the mixture as it does. But when the throttle is steady the
mixture is controlled by whichever jets are relevant for that
throttle position.
But what I wonder is why MOST carburetors, from old Amals and
Bings, to modern Mikuni and Keihin flat slides, get by fine
without pumps. And similarly, although virtually all (non
fuel-injected) car engines have accelerator pump carbs, the
traditional choice of car hot-up folk when I got old enough to
notice, was the SU which was a CV carb, with no accelerator
pumps.
Even on the same engine. So it's not that some engines have some
tendency to be lean when accelerating from idle, needing a
pumper to fix, because you an fit a non-pumper to a Ducati and
with correct jetting it will accelerate off idle just fine. And
BMWs are another good example, because some of the 1980s
R-series bikes has Dell-Orto pumpers, and some have the CV
Bings..........
Wikipedia says:
"Liquid gasoline, being denser than air, is slower than air to
react to a force applied to it. When the throttle is rapidly
opened, airflow through the carburetor increases immediately,
faster than the fuel flow rate can increase. This transient
oversupply of air causes a lean mixture, which makes the engine
misfire (or "stumble")—an effect opposite what was demanded by
opening the throttle. This is remedied by the use of a small
piston or diaphragm pump which, when actuated by the throttle
linkage, forces a small amount of gasoline through a jet into
the carburetor throat.[13] This extra shot of fuel counteracts
the transient lean condition on throttle tip-in."
But that doesn't explain why so many motorbike carbs get by
without a pump. A bloke told me once that a non-pumper slide
carb actually performs a function not unlike a pumper, in that
when you open the throttle quickly from idle, the needle, which
has been (when the slide is down) sitting in the needle jet
immersed in fuel, drags up with it a quantity of raw fuel to
enrichen the mixture during the time when the throttle is open
and the revs start to build- which is just what the pumper does.
But then, that phenomena (of the needle drawing up some raw
fuel) must also happen with pumper carbs so they should get a
double dose............
So, I don't know the answer.......... But I do have another
question........... Bikes with pumper carbs (really Ducati
V-Twins are my only experience) can be quite economical, despite
the fact that there's this big gush of fuel squirted in every
time you open the throttle, whereas my BMW G/S gets appalling
economy, despite having these supposedly efficient CV-type
Bings......
Its all a bit of a mystery.....
Nitram ??? ???
#Post#: 1072--------------------------------------------------
Re: Carburettors
By: cloggy Date: October 6, 2015, 4:20 am
---------------------------------------------------------
Whatever, my tappets start off quiet then get louder as the
engine warms up. I've frequently checked compression after
extended thrashing and the compression hasn't diminished nor has
the noise....... I haven't set them at no clearance as advised
#Post#: 1073--------------------------------------------------
Re: Carburettors
By: Falconefan Date: October 6, 2015, 11:36 am
---------------------------------------------------------
Hi Guys,
The only reference I have come across regarding the different
flywheels is in the workshop manual. It refers to (and has
photos) flywheels of 270mm and 225mm diameters - both shown in
the 'miliatary' manual.
I must say that the 30mm pumper (simple piston type on the VHB
C) was much more responsive to a handfull of twist-grip. The
VHB A has a notable hesitation when opening up, so I might go
back to it but play about with the jetting and slide. As it
was, I was gassing anyone following behind me. All that had
been done, was the main and idle jet replaced with larger ones,
without any regard to the needle or slide cut-up.
On a different note - that of fork oil. I spoke to a guy in the
technical dept of a lubricant firm regarding Shell Tellus 33.
He confirmed my findings that it is now Tellus 68 (the
difference is between pre ISO and ISO ratings) and is at the top
end of SAE 20 - double that that I have read suggesting 10W fork
oil. The good news is that rather than buying 205 litres of it,
you can get a single litre through good old eBay here:
HTML http://www.ebay.co.uk/itm/300854448851?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Essentially, he said that any ISO 68 mineral based hydraulic oil
with a zinc wear additive will be fine.
Best wishes,
Susie
*****************************************************
DIR Next Page