what liquid you use should not really matter. Once carb is already set and you are synching the other 3 to it. As long as the same substance is used in all 4 columns you will get a good sync.
ST1100 Gas Mileage Decreasing
- Thread starter paulcb
- Start date
Please Google "homemade carb sync tool". There are many versions out there. I think if you look at the fact that they show the DIFFERENCE in relative vacuum, things will be a little clearer. The lower specific gravity, the more relative difference is easily shown. I used ATF in my home made unit and restrictors to minimize the bounce in the tubing. With Hg, the bounce is less noticeable (have that unit too). Some use two stroke oil, compressor oil.....there are many possibilities. Most pick a fluid that won't damage the motor in the event of a leakage causing ingestion. Hung the tubing on a stepladder, works like a charm, honest~!but ATF has a specific gravity lower than water, so the column would be even higher than if you used water.
P.S. The joke was understood
Last edited:
OK, yes I understand about relative vacuum and absolute vacuum, so now I understand that's what you were talking about. In the original context we were talking about an absolute vacuum gauge setup, and you never mentioned differential pressure in your original post, so it wasn't clear that was what you meant. Yes, I'm familiar with all the concepts, but never actually built a homemade tool.
One question about using relative vacuum, you want to enable the vacuum from two cylinders into the hose at the exact same time so that you don't suck the fluid into the engine before the vacuum balance is established. When you start the bike with the vacuum lines attached is that usually safe enough that it doesn't suck any fluid into the engine?
Last edited:
Hasn't ever been an issue with the MP mercury stixs, but the glass tubes are also really long. Have heard of it happening to a couple fellow XS'ers with no damage, but the fumes were devastating
On an associated note, I'll be using the Morgan CarbTune on my XS Venturer when finially gets here from across the pond. I'll do a comparision to my Merc. stixs and report if anyone's interested.
Yes. ATF won't hurt it anyway.
There are quite a few videos on Youtube in that Google search showing the procedure and operation. The length of the tubing is your determining factor as to the ingestion question. The bottom line is that the I.D. size of the tubing will not allow that drastic of an air volume change unless there's a leak. Some, including me, use restrictors (tiny air openings) inside the lines which slow the air volume movement much more. This effectively reduces the bounce of fluid in that particular tube when the vacuum value drastically changes due to the piston/valve intake stroke. Not doing the math, but most procedures are to be done at "idle" 500-1500 RPM, which means the pulses are "pretty quick" and the bounces in each tube are fairly smooth. I think I could get my Shadow down to about 300 RPM with a good sync, but that was too low for the charging system for idle speed. (83 model year)
For about twenty bucks you can build your own and impress your riding buddies with how well and accurately it works, I did.
Re: ST11 Gas Mileage Decreasing
I fail to see how using a Flowmeter is not giving the "relative" levels, since the device IS inserted into each air horn with the engine running at the same RPM and all four cylinders read the same after adjustment, but whatever works for you is always your choice.
ST1100Y
Site Supporter
Re: ST11 Gas Mileage Decreasing
Yeah, but to do so you'll have to remove lid and filter, thus already messing up airflow, pressures and volumes...
I gotta laugh at some of the purists out there who spend $$$$ on the merc tubes, etc, to get just the *perfect* carb sync and then go and cheap out on a crap K&N air filter, which alters Mr. Honda's intended intake filtration and flow anyway!
Bottom line is . . . . RESULTS.
I'm quite happy with mine, but you all can carry on seeking your idea of perfection with tubes of liquids and such and those of us who get the results that work for us with a Flowmeter will do it our way. Oh, by the way, for all the purists, if you haven't tried it, don't knock it.
Bottom line is . . . . RESULTS.
I'm quite happy with mine, but you all can carry on seeking your idea of perfection with tubes of liquids and such and those of us who get the results that work for us with a Flowmeter will do it our way. Oh, by the way, for all the purists, if you haven't tried it, don't knock it.
Agreed, it all depends on what YOU are satisfied with for YOUR machine(s). To continue, we should include oil preference and best tires here~!
There's no question on that! . . . . . is there?
Re: ST11 Gas Mileage Decreasing
Have you ever read the procedure in the Honda ST1100 service manual?
The carb sync adjustment screws adjust throttle plate relative position between TWO carbs, like carb #1 and carb #2.
As I said before, you must be able to see the relative vacuum levels of ALL FOUR CARBS simultaneously.
This can be done with a four channel manometer (such as from Motion Pro).
It is IMPOSSIBLE to do this with any kind of an air flow meter.
IMHO
Have you ever synchronized carbs on a motorcycle engine?
Have you ever read the procedure in the Honda ST1100 service manual?
The carb sync adjustment screws adjust throttle plate relative position between TWO carbs, like carb #1 and carb #2.
As I said before, you must be able to see the relative vacuum levels of ALL FOUR CARBS simultaneously.
This can be done with a four channel manometer (such as from Motion Pro).
It is IMPOSSIBLE to do this with any kind of an air flow meter.
IMHO
ST1100Y
Site Supporter
Re: ST11 Gas Mileage Decreasing
Not that I'd tried that bugger (out of interest), but it a) requires at least one other person being busy swapping the instrument between the snorkels and b) did a re-check with a 'real' 4-channel carb sync tool and closed air-box reveal offsets...
I however do see issues with a liquid filled carb meter getting the fluid getting sucked out (like when having to restart the engine after a required cooling down phase, or operating the throttle to clear the throttle plate linkages after every adjustment step...)
I'm very happy with the older version of a Vacuummate ; being bike powered it also features an accurate tachometer, aiding the process.
Next on my list/shelf is the Morgan Carbtune; reasonable priced, quite accurate and not using liquids also fully safe to operate.
#1, #3 & #4 need to be adjusted towards the fixed mains carb #2; the puzzle is that i.e. any change on #4 will influence #1 & #2 and vice versa, thus requiring constant matching on all 3 adjusters, done careful, handling a flash-light and the extra long #2 Philips as the linkages are pressure sensitive, followed by a minor blip on the throttle to free any tension in the actuation.
For a total accurate setting, including equal idle mixture on all 4 cyl, I'd really like to have a quality emission sniffer and appropriate ports welded into the downpipes... yet I still failed to motivate myself into this expense...
Possible that a glass-plug, like the Colortune is a useful instrument for this, but also that means spending some cash for an equipment you'll rarely use...
Well, being a biped creature not having derived from insects I do face an haptics issue with the flow meter... ;-)
Not that I'd tried that bugger (out of interest), but it a) requires at least one other person being busy swapping the instrument between the snorkels and b) did a re-check with a 'real' 4-channel carb sync tool and closed air-box reveal offsets...
I however do see issues with a liquid filled carb meter getting the fluid getting sucked out (like when having to restart the engine after a required cooling down phase, or operating the throttle to clear the throttle plate linkages after every adjustment step...)
I'm very happy with the older version of a Vacuummate ; being bike powered it also features an accurate tachometer, aiding the process.
Next on my list/shelf is the Morgan Carbtune; reasonable priced, quite accurate and not using liquids also fully safe to operate.
#1, #3 & #4 need to be adjusted towards the fixed mains carb #2; the puzzle is that i.e. any change on #4 will influence #1 & #2 and vice versa, thus requiring constant matching on all 3 adjusters, done careful, handling a flash-light and the extra long #2 Philips as the linkages are pressure sensitive, followed by a minor blip on the throttle to free any tension in the actuation.
For a total accurate setting, including equal idle mixture on all 4 cyl, I'd really like to have a quality emission sniffer and appropriate ports welded into the downpipes... yet I still failed to motivate myself into this expense...
Possible that a glass-plug, like the Colortune is a useful instrument for this, but also that means spending some cash for an equipment you'll rarely use...
Re: ST11 Gas Mileage Decreasing
opcorn
Now, about the best oil and tires........
At the risk of :BDH:, Everyone has their own degree of accuracy that satisfies themselves. Not trying to "blow my own horn", but with a background of measuring instrumentation (aircraft and electronic) and the need to understand the scientific principles involved, I am probably the most pleased with my $20 home made unit. Never falls out of accuracy, never needs re-calibration like any mechanically moving device. Not an environmental hazard like my Hg unit. As long as the clear tubing and restrictors are not blocked, the ATF gives me a reading I'M happy to run. Don't mind loaning it out either, I can always make another cheap. Remember, even your torque wrenches require periodic calibration, how many of you do that ?
opcornNow, about the best oil and tires........
Re: ST11 Gas Mileage Decreasing
OK . . . time to give it a rest Tim. Since coming here you have had one tone in all your posts - my way or the highway. I, for one, am getting tired of it.
Re: ST11 Gas Mileage Decreasing
.
Irregardless of your impression, he IS absolutely correct in this case. Carb syncs on multicarb scoots IS done with all intake in place as it is normally ridden. Absolutely CANNOT be done correctly unless all four cyl. vacuums can be seen at same time. Also, between adjustments when bike is off, it IS important to snap the throttle several times to seat adjustment screw threads, repeating this process and re-checking sync several times IS necessary in order to have same vacuum across all four intakes. Sorry that the Flo-Meter is 'snake oil' at best........for THIS application. It definitely has its uses........this is NOT one of them
.
Re: ST11 Gas Mileage Decreasing
READ MY LIPS . . . I'm quite happy with my Flowmeter results. Have been so with the same bike for 18 years, carbs never touched otherwise. You ace mechanics can do whatever you want with your bikes.Irregardless of your impression, he IS absolutely correct in this case. Carb syncs on multicarb scoots IS done with all intake in place as it is normally ridden. Absolutely CANNOT be done correctly unless all four cyl. vacuums can be seen at same time. Also, between adjustments when bike is off, it IS important to snap the throttle several times to seat adjustment screw threads, repeating this process and re-checking sync several times IS necessary in order to have same vacuum across all four intakes. Sorry that the Flo-Meter is 'snake oil' at best........for THIS application. It definitely has its uses........this is NOT one of them
Re: ST11 Gas Mileage Decreasing
For those that understand, no further explanation is needed. For those that don't, no further explanation is sufficient.
Re: ST11 Gas Mileage Decreasing
I guess we can only agree to disagree on this subject. Holy SMOKES! I was never expecting there to be such STRONG opinions on this subject.
I will continue to follow the prescribed (correct) procedures from the vehicle manufacturer, thank you.
There is no such "tone" in my posts. This is a false accusation. You have not answered my two relevant questions.
I guess we can only agree to disagree on this subject. Holy SMOKES! I was never expecting there to be such STRONG opinions on this subject.
I will continue to follow the prescribed (correct) procedures from the vehicle manufacturer, thank you.
Re: ST11 Gas Mileage Decreasing
I have recently seen at least one other example of "snake oil" thinking with motorcycles. That would be, the use of "Dyna Beads" in tires, to avoid conventional wheel balancing. (I hope I'm not stirring the pot here).
"the Flo-Meter is 'snake oil' at best..." I never thought about this! So this problem is actually WORSE than I thought. I didn't realize that this was such a common mistake!Irregardless of your impression, he IS absolutely correct in this case. Carb syncs on multicarb scoots IS done with all intake in place as it is normally ridden. Absolutely CANNOT be done correctly unless all four cyl. vacuums can be seen at same time. Also, between adjustments when bike is off, it IS important to snap the throttle several times to seat adjustment screw threads, repeating this process and re-checking sync several times IS necessary in order to have same vacuum across all four intakes. Sorry that the Flo-Meter is 'snake oil' at best........for THIS application. It definitely has its uses........this is NOT one of them
I have recently seen at least one other example of "snake oil" thinking with motorcycles. That would be, the use of "Dyna Beads" in tires, to avoid conventional wheel balancing. (I hope I'm not stirring the pot here).