HHMMM, neet stuff you two.......steve #1131
----- Original Message -----
From: Rey Kirkman <[EMAIL PROTECTED]>
To: V-MAX TECH LIST <[EMAIL PROTECTED]>
Sent: Sunday, April 09, 2000 12:21 PM
Subject: Re: Yamaha CICS
> I am traveling down the same road as Bill in that I am bringing an '86
> Venture up to Max specs. There is more in common between the two motors
> than there are differences. Their origin is the same, and it is useful to
> take a look at old road tests. One obtains clues as to the "whys" of
Yamaha
> engineering - particularly why some modifications work and others don't.
In
> the June '83 Cycle road test of the first Venture the writer states that
the
> seed for the motor began seven years before.
>
> "Now, a short history lesson. Several years ago, in 1975, Yamaha
began
> work on a (sic) European endurance racer powered by a non-counterbalanced
> 90-degree V-four. This machine led the way to the 550cc Vision, which
> essentially was the endurance racer sawed in half lengthwise, with added
> counterbalancer and its V-angle tightened to 70 degrees. It shared the
> racer's narrow valve angle, downdraft carburetion and liquid cooling. It
> even had the racer's frame layout. Then, two years ago, Yamaha launched
the
> V-four Venture project.
>
> The new V-four isn't a Double Vision; there are too many design
> departures for that. Examples: the Venture's crankcases split
horizontally,
> the Vision's part vertically; the Venture's cylinders are molded
integrally
> into the crankcase casting, the Vision has separate cylinder blocks; the
> Venture's 76x66mm bore and stroke differ radically from the 80x55mm Vision
> proportions.
>
> Despite these departures, a marked similarity remains in certain
areas,
> enough to stamp the signature of the same engineering group on both
engines.
> Like the Vision's the Venture's cylinder head has offset inlet ports. In
> this system, one intake valve lies at the end of the curved inlet port;
its
> mate gets a straighter shot from the carburetor. The offset "masked"
valve
> gets the YICS (Yamaha Induction Control System): a small feeder tube,
> sitting just upstream from the valve head, squirts extra fuel/air mix from
a
> separate plenum chamber and creates a swirl to increase combustion
> efficiency.
>
> A concern for charging and combustion efficiency is also found in the
> gernal design of the cylinder head. The Venture uses a narrow 35-degree
> included valve angle (one degree narrower than the Vision's), which
results
> in an extremely compact combustion chamber. Thanks to a shallow chamber
> roof, tall pent-shaped pistons aren't necessary; although flat-topped, the
> pistons pump compression to 10.5:1. A flat piston top encourages good
> cylinder filling when the inlet valves are barely off their seats. A
> compact chamber, moreover, allows fast flame-front travel during
combustion,
> which not only helps power but also reduces exhaust emissions."
>
> Joe Minton wrote for Rider magazine in May 1983:
>
> "There are four swirl-inducing Y.I.C.S. chambers that feed a high velocity
> stream of mixture to each intake port as the valve opens. These small
> chamber are not inter-connected as with some other Yamahas because, I
> suppose, of the uneven firing order of the V-engine. The U.I.C.S. units
are
> maintenance are except for the connecting hoses. Yamaha claims improved
> fuel mileage and power from this design feature."
>
> Seems to me that the Y.I.C.S. chambers must have a fuel/air source from
the
> carburetors. I think Bill is on to something here. Maybe the design was
> dropped from the Max because of cost and the feeling that the Max had
> "enough" power.
>
> It would be interesting to see a dyno sheet from Bill's motor with and
> without the Y.I.C.S. It may well be that the absence of Y.I.C.S. is part
of
> the reason for the troublesome mid-range flat spot in Max motors.
>
> Rey Kirkman
> ----- Original Message -----
> From: Bill D. Miller <[EMAIL PROTECTED]>
> To: V-MAX TECH LIST <[EMAIL PROTECTED]>
> Sent: Sunday, April 09, 2000 7:48 AM
> Subject: Yamaha CICS
>
>
> > Here's a problem one of you VMaxers may be able to solve: early
('83-'85?)
> > Ventures used a CICS "system" comprised of a 3"x12" plastic box with
four
> > sealed chambers; each of which was plumbed into the intake port of one
> > cylinder via a rubber hose (look carefully at your VMax cylinder head
> > castings and you'll find vestigial bosses near each port). The chambers
> > evidently acted as vacuum reservoirs -- but I can't imagine why they
were
> > needed or what, if anything, they did. There is no direct connection to
> the
> > carburetors (other than through the intake port) but I can run the
Venture
> > with a wide open airbox and it seems to experience none of the usual CV
> > carburetor problems (coughing, bogging, excessive leaness). In fairness,
> it
> > has been suggested that the explanation for this phenomenon is size of
the
> > early Venture pilot jets (42.5), so maybe it's not related to the CICS.
> >
> > The Service Manual offers no description of the operation of the CICS --
> and
> > provides no service guidance. Just another cute 80's acronym to sell
> bikes?
> >
> > I'm mounting 1985 VMax heads & vboost on a 1300cc Venture motor (for
> > installation in my '83 Venture) and wonder if drilling those bosses and
> > remounting the CICS would improve/detract/not affect performance. I'll
be
> > using the VMax flywheel and pickups with the '83's ignitor unit. Your
> > comments would be appreciated -- but I subscribe to the digest so won't
be
> > able to reply to any questions 'til the next day unless you want to
> contact
> > me off list.
> >
> > TIA
> >
> > Bill Miller
> >
> >
> >
> > .............................................
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> > .............................................
>
>
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