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Re: Throttle shaft wear and TwinMax calibration (was ABS)
- Subject: Re: Throttle shaft wear and TwinMax calibration (was ABS)
- From: Robert Silas <robert.silas@xxxxxxxxxxxx>
- Date: Mon, 14 Nov 2005 11:39:23 -0500
Where did you obtain an air-horn and what is the installation involves???
----- Original Message -----
From: Ben Barkow
Sent: Monday, November 14, 2005 11:11 AM
Subject: Throttle shaft wear and TwinMax calibration (was ABS)
I've been riding around with my dual vacuum gauges recently. With
liter-sized engines, you get an awful lot of vacuum during engine
braking. It goes beyond 20 inches of mercury. I'm not sure how far
since you need to use heavy needle damping (AKA "snubbing") and so
brief transients are hard to catch. Folks who only have TwinMaxs can
check this using the Min scale with the meter connected to just one TB
- see below. Using a TwinMax as a vacuum gauge might destroy your
TwinMax meter so work carefully.
If my understanding of pressure is correct, since an inch of mercury is
like .5 psi, and with butterflies about 2 sq inches, you can have 20
pounds tugging on the little butterfly shaft. So, I'd expect lots of
shaft wear, as Paige has noted. And for fueling to work right, you need
to have some degree of precision at small openings.
I borrowed a TwinMax recently. Although I think dual vacuum gauges are
the right way to tune, the 9 volt unit I borrowed was very nicely
behaved and fair to the two sides - checked yours recently? Why not...
do you believe in the Tooth Fairy?
Here's how this unit was calibrated:
Max: each meter number is one inch of mercury (plus or minus 3 for full
Middle: each number is 7 inches
Min: each number is 10 inches
I'd say you are well-synched when you have deviations within plus or
minus half an inch, and particularly at the point that matters the
most, that first take-up of the cable slack.
Don't forget to re-connect your TB balance tube when the synch is over.
Ben Barkow, Toronto... 39 seasons on Beemers, 44 as a biker
1961 R69s/rod, 1967-1999... really sup'ed up and fast
1984 R80RT/rod, 1998-2005 5 extra peak ponies in a wider flatter power
much modified 2-into-1 exhaust, CR 9.5, Keihin PJ 34mm oval carbs,
Uni filter, dual-rate springs with cartridge emulators, BT45/S11,
1999 R1100S, 2004- Leo Vince exh, JetHot coatings, Techlusion 1031,
large sticky foam filter, TB balance tube, 26 inch windscreen, air
horns, Diablo Stratas
On 2005 Nov 12 , at 4:47 AM, oilheads-digest wrote:
> Date: Fri, 11 Nov 2005 22:44:27 -0500
> From: plpklt@xxxxxxx
> Subject: Re: ABS
> A while back on the list there was mention and even a like to
> replacment of the TB butterfly shaft. Can anyone send me that link
> again, and how hard is it to replace it? My right Throttle body is
> making so much noise with the rattling from the trottle cable plate
> that the shaft must be very loose... It shoulds like I have never
> adjusted the valvles but is just the plate making all that noise. I
> wouldn't believe it but if you touch it the noise stops so I'm