PipL
2012-12-15 16:14:44 UTC
As my expensive but lamentably non-adjustable Davida vac gauges have gone out
of cal with each other, I ordered a pair of standard 63mm gauges off Ebay,
guessing that the nut & tail on the current ones was also 1/4" BSP.
They were considerably cheaper than the old ones, but I had a couple of
concerns: how consistent they would be with each other and how well they'd
take to the pulses from individual cylinders, however, the tails from the
Davida ones had built-in damper adjustment screws and the Davida gauges
themselves had no obvious built-in damping, so I had high hopes. I figured
that at worst I'd have to add extra inline damping in the form of a restrictor
on the hoses.
There was one other thing: the Davida ones were specifically designed as
automotive gauges and scaled to -600mb; the new ones would be full -1000mb, so
I'd lose a touch of accuracy there.
Well, I picked them up from the Post office this morning. They seemed
consistent enough with each other, always a benefit when balancing throttles,
and they did indeed take the Davida damped tails, although the nut only
screwed on a couple of turns. Better yet, the case screws had matching
positioning & spacing, so they mounted straight onto the Davida backplate.
Once fitted to the1200, there was a bit of needle flutter, but I made do by
pinching the hoses to adjust the the damping. Later, I tried using an
adjustable spanner to clamp them, which sort of worked - I would have needed
three hands to do the high RPM check otherwise.
After my last attempt there really wasn't much throttle balance adjustment to
do, but I got the higher RPM adjustment done as well this time, again, hardly
any adjustment needed.
Finally, I grabbed the laptop and reset the TPS, though for some reason it
took several tries for the software to connect to the cable: not sure why that
was.
So, all in all, a good bit of fettling; I'm pleased. The throttle response had
got slightly sharp just off idle after I did the valves a few weeks ago, but
it feels much smoother now.
I've subsequently added damping screws to the manifold stubs, to remove that
needle flutter, though that might have been unnecessary: there was a bit more
adjustment in the screws in the Davida tails, once I really tghtened them up.
To celebrate, I washed both Guzzis.
of cal with each other, I ordered a pair of standard 63mm gauges off Ebay,
guessing that the nut & tail on the current ones was also 1/4" BSP.
They were considerably cheaper than the old ones, but I had a couple of
concerns: how consistent they would be with each other and how well they'd
take to the pulses from individual cylinders, however, the tails from the
Davida ones had built-in damper adjustment screws and the Davida gauges
themselves had no obvious built-in damping, so I had high hopes. I figured
that at worst I'd have to add extra inline damping in the form of a restrictor
on the hoses.
There was one other thing: the Davida ones were specifically designed as
automotive gauges and scaled to -600mb; the new ones would be full -1000mb, so
I'd lose a touch of accuracy there.
Well, I picked them up from the Post office this morning. They seemed
consistent enough with each other, always a benefit when balancing throttles,
and they did indeed take the Davida damped tails, although the nut only
screwed on a couple of turns. Better yet, the case screws had matching
positioning & spacing, so they mounted straight onto the Davida backplate.
Once fitted to the1200, there was a bit of needle flutter, but I made do by
pinching the hoses to adjust the the damping. Later, I tried using an
adjustable spanner to clamp them, which sort of worked - I would have needed
three hands to do the high RPM check otherwise.
After my last attempt there really wasn't much throttle balance adjustment to
do, but I got the higher RPM adjustment done as well this time, again, hardly
any adjustment needed.
Finally, I grabbed the laptop and reset the TPS, though for some reason it
took several tries for the software to connect to the cable: not sure why that
was.
So, all in all, a good bit of fettling; I'm pleased. The throttle response had
got slightly sharp just off idle after I did the valves a few weeks ago, but
it feels much smoother now.
I've subsequently added damping screws to the manifold stubs, to remove that
needle flutter, though that might have been unnecessary: there was a bit more
adjustment in the screws in the Davida tails, once I really tghtened them up.
To celebrate, I washed both Guzzis.
--
Pip
Pip