- The Response - I had the
CV manifold system on my Banshee, and I loved it! When it
comes to the technical aspects of motors and other things
mechanical, I am "functionally illiterate". When I hang
out here, I find out how little I know. I really like
reading the posts on this board when you guys (Rick,
Backcountry, trax310m, High output, YSF200 and more)
analyze and discuss what makes motors go fast and
why.
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- My experience with the CV
system , THE WAY IT WAS SET UP on my Banshee was as
follows;
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- When I got the CV manifold
system installed, I was told that it would increase
torque and give better low end to midrange response. This
was not what I experienced. But the actual results were
far different and better than I dreamed of! What I got
was not what I had expected. I did not notice much
difference in throttle response, in fact the bike was
very peaky. The bike pulled incredibly hard from upper
mid-range to WOT. The bike was awesome in the way the
motor would rev. I loved it! It was a
screamer.
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- Although I don't know details
like squish, etc. I'll list what I do know about the
setup.
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- Trinity CV manifold, Trinity
Stage III porting, Toomey T5s ,35 PWK carb, Cool head
with 17 cc domes compression 180 in one cylinder and 182
in the other, usually ran a 165-170 main, a 168 pilot and
DGJ needle with the clip on position 5 (all the way
down). This motor was a high revving screamer. I NEVER
got beat racing at the hills by any 350, 370 or 420
Banshees(at this point, out of respect to all you 4Trax
enthusiasts, I am going to leave those comparisons out of
this message) the only Banshees that beat this motor were
big bore bikes. On the dyno, all the power was at high
revs, peaking out at 74 hp. That was my experience with
the CV setup. I LOVED it for what it was in my bike, but
it was a peaky motor that revved high and pulled HARD at
high revs.
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- I am writing about it in the
past tense because I am just about to take delivery of my
new motor (next Tuesday in time for Easter week at
Glamis!). The only (non-Honda) bikes that beat that motor
was big bore Banshees, so I had to have one! Trinity is
building my 500 cc alcohol motor, and Harry got the
aluminum sleeves today, so he's going to do the porting
and milling the cylinders before he sends the cylinders
to get the Nikasil plating. The crank is done (10 mm
stroke) and I think they have set Thursday to do what
they are going to do to the cases (match port? Or
something like that). Anyway, I'm really
exited!
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- Back to the CV system, I am
selling my whole top end as described at the beginning of
this message, ported cylinders, pistons, etc., CV
manifold, 35 PKW, Cool head and domes for $1000.00 or
best offer. (Toomeys not included) The price of the
individual components is about $1600 (not including the
porting).
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- John
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- They are really made to enhance
low end power. I haven't tried them, but from what I
here, "they suck!!". I think that he would be better off
buying the larger carbs. He may even want 34 or 35's if
top end is the quest. Allot of my friends are going to
the 35's. How does he feel about that MSD ignition?
Sounds like a super fast bike.
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- Brandon
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-
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- Hey Brandon, thanks for the
reply. I've heard good and bad about the CV system too,
some people say its great; the best---then others say it
doesn't rev worth a darn...... I have heard about a lot
of people going to 35 PWK's. A local shop here, JSD
Racing, recommends running regular 35 PWK's, not the Air
Striker PWK, on most of their "hotter" ported motors for
bigger guys. So we're trying to figure what's the best
right now.... the CV system is about 4 bills, but a set
of PWK's slightly used run around 220-250 around here, so
there's a price difference involved.
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- I talked him into the MSD, I've
got one on my R and WILL NOT ever go back to stock. The
MSD is far superior to any thing that stock can ever do.
The timing curve is adjustable which is a big plus, real
hot spark.... the works, I really recommend it. I've
gotten nothing but top notch customer service from MSD.
Sand sport magazine did a dyno test on a slightly mod'd
Banshee, and they said after they tweaked and twiddled
they gained 5 more HP..... that's considerable..... You
can run lots of initial advance, but the curve tapers to
a more friendly retard at higher revs where less ignition
lead is needed. Too much advance at hi-rev can lead to
the motor working against itself.... BAD!!! I say buy an
MSD you won't be disappointed. So what's up with your
ride lately anyways, I liked peekin' in and reading your
posts to Trax.......
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- Backcountry
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- CV carbs on a Banshee... Another attempt at "jet it
and forget it?" Selling it as a low RPM thing (read - rob
HP). The Banshee was never sold as a "slow poke" quad, so
why is everyone trying to make them that way? What's the
world coming to and why do we need low end on our
Banshees? Why can't people let the quads be what they are
and stop pretending to make them into something they're
not.
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- I was looking at a set of RZ350 barrels that were
getting a bore job today - you know the Banshee barrels
WITH the power valves. They sure look like they should
have been OEM on the Banshee. But then again maybe Yamaha
didn't include them because they didn't intend for the
Banshee owner to want or need low RPM power. The RZ350
street bike will spend much of its time at stop lights
and in traffic where the grunt might be helpful but the
Banshee is to be ridden fast and hard without ever
looking back, needing to go below 6000 RPM or asking its
owner to explain why or why not.
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- There are those who read "stones" to predict the
future. You know, they throw the sacred stones on a table
in front of them and "look" into them. When reading them
it's not the position they land in that matters - its how
the interpreter feel about them landing in that
position.
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- Rick
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- The latency of the reeds and the ram effect of the
incoming charge will keep the reeds open much longer than
we'd like to think. Two stroke engines will still have
their reeds open when the piston is passing 90° ATDC
or more. They don't close at TDC or a few degrees after
like it seems they should. Because of this, the twin
cylinder Banshee is indeed feeding from a single 34 mm
(or was it 35 mm) carb using the CV system. While one
piston is going down at 90° ATDC (reeds still open)
the other piston is going up at 90° BTDC (its normal
intake cycle) - making the carb feed both sides at the
same time.
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- Rick
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-
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- Interesting, that (the latency
in the reeds and the ram air effect) kind of backs up a
tech. paper I read a year or so ago, that was on a strobe
test done on reeds under various engine speeds loads, so
on. The testers were very surprised to see how much
movement there was in the reeds, torsional movement, wave
like oscillation within an open reed, stuff that they
thought that they wouldn't find. Like most of us, we
figure a reed acts like a door, either its swung open or
swung close, nothing too wild within that movement,
however this paper said that the was LOTS of extra
movement.
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- So I guess with that, the CV
system is NOT a worthy investment with this type motor.
What would you recommend for carb size and type for this
application??
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- Backcountry
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-
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- There's some good SAE tech articles like that too. I
have that here somewhere... It seems that the reeds
twisted, bounced of their seats and did any number of
things that would seem curious, at best.
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- What first threw me was the name CV - constant
velocity. This lead me to think of constant velocity type
carbs - 4 stroke thing. In this case they are using one
carb to feed both cylinders and in doing so they are
mellowing out the power by virtue of under carbureting
the motor. Anytime you take away CFM's from the intake
the power will be more mellow.
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- I'm from the school of every cylinder gets its own
carb and pipe. Installing and jetting smaller individual
carburetors to each cylinder will produce similar
results, though in theory it should have more on top.
Small carbs carburet better as well.
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- Since the Banshee is a zero deck motor, it makes it
more difficult to tame the porting to match to the
smaller carburetors. More difficult, but not impossible.
It is possible to mill 1 to 1.5 mm's from the bottom of
each cylinder to lower the power peak as well. Adjust the
head so the piston - it will come up above the bore -
still has a properly set squish. It will be fine running
this way, in fact I set up a LT500 (also a zero deck
motor) that way several years ago that worked fine. With
a stock TRX barrel it is possible to mill more than 1 mm
from the bottom without having the piston come above the
barrel. It is not impossible to mill a couple of mm's
there (watching the liner to crankshaft clearance) to
make it perform like a totally mellow ride. Give it a
good squish and compression and you have the making for a
wonderful learners bike or a bike for the spouse who is
intimidated by sudden power surges.
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- Rick
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