Jai -DSA wrote: ↑Sat Sep 23, 2023 10:28 pm Big update and great news!
To date, I'd synched the carbs several times using my Carbtune pro. But multiple people on here saying that my issues sound like unsynched carbs and Cliff's suggestion that maybe my Carbtune isn't working properly got me thinking. So: I re-read the Carbtune manual. It tells me I am supposed to be hanging the carbtune off the handlebars of the bike - I hadn't been doing this. Instead, I'd been laying it on the false tank, almost horizontally. I did as the manual said and hung the instrument off the bars, and lo and behold...it indicated no vacuum. On any of the cylinders. That obviously didn't make any sense, since the bike's engine was running. If I blipped the throttle, I briefly got a reading, but only from 3 of the cylinders. [/size]If I angled the carbtune so that it was more horizontal (what I had before), I started getting a reading from all 4. But now my confidence in the reading was pretty badly shaken. So back I went to the manual - and it said that for bikes pulling low vacuum, one alternative is to hand the carbtune upside down. Gave that a try, and now I had readings. Using this, I resynched the carbs. Let it sit overnight, then took it for a test ride just now.
I discovered something eye-opening about the Carbtune Pro rubber hoses quite by accident yesterday evening.
I wanted to hang my 4 vacuum gauges synchronizer panel
off to the left side of trike for a clearer view of them from the right side and needed longer rubber hoses to reach all 4 intake manifold synchronization fittings on my '75 GL1000.
Hmm...my Carbtune Pro has synch hoses which are a lot longer, so I swapped the vacuum gauges adjustable needle snubber valves into those longer Carbtune Pro synch hoses and gained at least another foot.
note: the engine had been running until maybe 5 minutes before this photo was taken. I had previously noted with prolonged sessions of vacuum pump balancing these 4 vacuum gauges needles, they invariably would linger slightly off their balanced set point for a while. (never timed it...let's say overnight) The 4 vacuum gauges panel was hanging with its bottom edge swung away from vertical, and was making its 4 individual vacuum gauge faces increasingly difficult to read, while I was leaning over from trike's right side attempting to balance the running engine's left and right cylinder banks.
The 4 vacuum gauges' needles had previously been snubbed sufficiently to provide slightly twitching readings, but became difficult to see clearly at close range while attempting to adjust the left rear synch screw.
I soon stood straight up to get a better view of the gauge faces and discovered them too far underswung and reached under the bottom edge of the gauges panel to swing them upwards. I would guesstimate no more than 30ish degrees.
Suddenly all 4 vacuum gauge needles, in unison stopped twitching.
Still holding the vacuum gauges panel at that 30ish degrees angle I opened the snubber valves 1/2 turn . Nothing.
1 turn. Nothing. all 4 vacuum gauge needles are dead still. Hmmm
I am pretty well exhausted anyways and release the vacuum gauges panel to swing backwards from vertical, then sit down.
Trike's Engine is still running and I look across the top of the shelter and those 4 vacuum gauge needles are all busily (wildly) oscillating again. note- all 4 vacuum gauge needle snubber valves were still an additional 1 turn open.
What I am observing is a situation where the Carbtune company's synch hoses are basically hanging straight down from my 4 vacuum gauges panel in comparison to the 180ish degrees arching over profile the hoses take on when plugged onto the top of the Carbtune Pro manometer? barb fittings.
Perhaps that is a reasonable assessment why your personal Carbtune Pro was not responding, at all, to your bike's running engine when its manometer case is suspended as intended, vertically.
The very flexible Carbtune Pro rubber hoses will arch when draped sufficiently and though not visible on their outer surface, collapse internally? Maybe yes...Maybe no.
Here's a photo of the Carbtune Pro to show fellows not familiar with its vacuum hoses' attachment details.