Webra 145 with Greve Pipe

[Jeff Hughes]

That's why I've gone to a Bolly muffler. I give up a few 100 rpms, but 
gain tractability.

> Thanks for reply,
> 
> I just came in from doing some pipe tuning and found that, if I peak 
the
> pipe, the engine won't come on the pipe from idle unless I pinch the 
fuel
> line momentarily, then it "jumps" on the pipe and holds the rpm.  If 
I
> richen it up a little the problem gets worse, to the point that the 
engine
> will die from loading up if I don't pinch the line.  Lengthening the 
pipe
> reduces the rpm but also softens the jumping effect.  I guess this 
is what
> the MC carb is all about with the Webra 145??????
> 
> I think I'll take your advice and run the pipe longer.
> 
> ----------
> >From: "Jeff Hughes" <jhughes at hsonline.net>
> >To: discussion at nsrca.org, <discussion at nsrca.org>
> >Subject: RE: Webra 145 with Greve Pipe
> >Date: Wed, Jun 18, 2003, 11:06 AM
> >
> 
> > It's really related to RPM. A two stroke has both ports open so 
some
> > the intake charge blows out the exhaust, the pipe sets up a 
pressure
> > wave which packs this back into the cylinder. As you can visualize,
> > with a fixed pipe length, this will only work at a specific rpm. So
> > props with the same load will use similar pipe lengths. But any 
change
> > that effects the RPM will require a pipe change. When I was 
running a
> > pipe on my 1.40, I deliberately ran it an inch long so it would 
start
> > to come on the pipe in the midrange, which softened the "peak". 
When I
> > ran dirt bikes, we set them so they were very peaky, all's we cared
> > about on them was HP.
> >
> >
> >
> >> You will also notice a difference in results when you use 
different
> > prop sizes. As a general rule you need to make the set-up longer if
> > you use a bigger prop. (Assuming that you had it right in the first
> > place.
> >>
> >> Bigger can mean diameter or pitch. Some sizes interchange well, 
For
> > example an APC 17 x 13 can swap with an APC 16 x14 with the same 
pipe
> > settings.
> >>
> >> Regards,
> >>
> >> Eric.
> >>
> >> -----Original Message-----
> >> From: discussion-request at nsrca.org
> >> [mailto:discussion-request at nsrca.org]On Behalf Of Lee Davis
> >> Sent: Wednesday, June 18, 2003 11:06 AM
> >> To: discussion at nsrca.org
> >> Subject: RE: Webra 145 with Greve Pipe
> >>
> >>
> >> The setup info I give on our web site is generic.  It works, but
> >> temperature, altitude and fuel type are a few of the variables 
that
> > can have
> >> an effect.  Lengthening the pipe enhanced the mid-range in the
> > particular
> >> case I mentioned, though I hesitate to make a blanket
> > recommendation.  I've
> >> set up engines for many people.  I doubt any two ended up exactly
> > alike.  As
> >> is the case for much of our equipment, manufacturer instructions
> > will get
> >> you going, but they are not necessarily the last word.  It is in 
your
> >> interest to experiment and optimize.
> >>
> >> Lee Davis
> >> Piedmont Models
> >> http://www.piedmontmodels.com
> >>
> >>
> >> -----Original Message-----
> >> From: discussion-request at nsrca.org
> >> [mailto:discussion-request at nsrca.org]On Behalf Of Keith Black
> >> Sent: Wednesday, June 18, 2003 1:39 AM
> >> To: discussion at nsrca.org
> >> Subject: Re: Webra 145 with Greve Pipe
> >>
> >>
> >> As long as we're talking about the Webra 1.45, RPMs and pipe 
length,
> > what
> >> are some experiences with the Webra 1.45 and the Greve pipe.
> > Piedmont's web
> >> site it recommends 27.5" to the first baffle, but recently Lee 
Davis
> > posted
> >> that he has his set at 28.5" to the first baffle.
> >>
> >> Mine's actually running pretty well at 27.5", I'm just wondering 
if
> > I can
> >> improve it by moving it back an inch.
> >>
> >> Lee, if you read this, why did you move yours out another inch 
over
> > what
> >> your web site recommends? What did this improve (top end, mid 
range,
> > etc.)?
> >>
> >> Does anyone else have experiences to share with this combination?
> >>
> >> Thanks,
> >> Keith Black
> >>
> >> ----- Original Message -----
> >> From: "Jerry Budd" <jbudd at QNET.COM>
> >> To: <discussion at nsrca.org>
> >> Sent: Wednesday, June 18, 2003 12:00 AM
> >> Subject: Re: Webra 145
> >>
> >>
> >> > >Let's try again - what rpm are you guys getting with what props
> > with the
> >> > >Webra 145?  I'm trying to tune mine with a Bolly pipe and have 
no
> > idea
> >> what
> >> > >to look for.  I'm trying both a 17X10 and 17X12N prop.
> >> > >
> >> > >Thanks for any suggestions.
> >> >
> >> > 82-8300 rpm when new, 85-8600 rpm after ~30 flights.
> >> >
> >> > Magnum #1, OS-F or YS plug, ES-2C140L90 pipe set at 23-1/4" 
baffle
> > to
> >> > plug, stock Mac's 2-1/4" rise header, and an APC 17x12 prop.  
The
> >> > Webra MC (mixture control) carb I'm using gives a dead linear
> >> > throttle response with NO jump onto the pipe.  Setup this way 
the
> >> > motor throttles exactly the same as a DZ but with better
> > performance.
> >> > With the stock ProMix carb it throttles a lot like the OS (rich 
in
> >> > the mid range).
> >> >
> >> > Jerry
> >> >
> >> > --
> >> > ___________
> >> > Jerry Budd
> >> > mailto:jbudd at qnet.com
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> >>
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