Here's the situation...My parents went away on a weeks vacation and, they left the keys...oh wait, wrong situation.
I've got a motion pro carb synch tool. Only problem is that its a few years old and two of the glass tubes are cracked. My question is, could I hook one of the good lines from the Motion Pro tool into the #4 starter valve and then synch one valve at time, leaving the other two valves connected to the vacuum fitting? My thinking is that since the other three valves are adjusted to the #4 valve's value, it wouldn't matter that not all of them are connected to the carb synch tool at the same time? Anybody see a problem with this?
I've done what you're talking about in theory, only a little different with very good results. I sync'd 1,2, and 3 to 4 one at a time, plugging the other 2 cylinders not being tested. I didn't have a mercury type tool, so I made one using about 30' feet of clear tubing the size of the ports (1/8" in think). I attached the tubing, in the shape of a big "U", to a board 6" wide and 6' tall. I filled the tube with 2 cycle motor oil so that it was about half way up each side (3 feet). I hooked one end up to number 4 vac port and then moved the other between 1,2,and 3 plugging the ones not being tested. I would adjust until the two side where even. I then went back and checked all a second time, just to make sure. If you think about it, using the oil is going to be more accurate. Mercury has a specific gravity of 847 lb/ft3, where as SAE 20w oil is 57 lb/ft3. This means that a pressure that moves mercury 1 inch will move oil 14.28 inches. Why do they use mercury? You don't need 6ft tubes. Why use 2 cycle oil? It's dark in color, and if you accidently suck some in, it not going to kill anything. With less then 1000 miles on my '06, some of mine where off as much as 7 inches of oil (about a 1/2 inch of mercury). It idled, and ran much better just off idle after I was done. Oh, don't forget to block off PAIR while you're adjusting.
Thanks coderider. I had actually made a manometer using clear tubing and 2-stroke oil, as demonstrated in another thread on VFRd. But I couldn't get the tubing to form an air tight seal around the t-fittings. That's why I was going to go back to my old Motion Pro tool. Perhaps I'll try what you mentioned, since I won't have to deal with all the vacuum fittings.
[image: View Post]FotoMoto, on Jul 13 2009, 11:33 AM, said:
It's really best to have all four readings going as sometimes adjusting one throws another out of whack (technical term); however,......
this is done with the 6 cylinder CBX as most folks don't have 6 gauge manometer laying around! Purist, of course, build their own.
I see no reason way all four at once would be more accurate. I would agree if #4 was adjustable also, you'd pretty much have to see all for at once or you'd be screwing around forever trying to get it right. In our case, all cylinders are set to a "standard", #4. I do, however, see where having all four at once would save time, no starting, stopping, and moving lines around.
Not sure what kind of fittings you used for your manometer, but mine holds a vacuum just fine.
As to the question. You can, but every time you make an adjustment, you're going to have to check the other two and mark/remember their levels, then make the next adjustment, rinse, repeat. Moving one affects the rest. Eventually you can work it down to a science, but it is still better and easier to have all cylinders hooked up at the same time.
[image: View Post]YoshiHNS, on Jul 13 2009, 12:14 PM, said:
Not sure what kind of fittings you used for your manometer, but mine holds a vacuum just fine.
As to the question. You can, but every time you make an adjustment, you're going to have to check the other two and mark/remember their levels, then make the next adjustment, rinse, repeat. Moving one affects the rest. Eventually you can work it down to a science, but it is still better and easier to have all cylinders hooked up at the same time.
In 4 channel manometer, the four tubes are join at the bottom. This is done so all 4 tubes are level when unit is level and no force is acting on any one channel. If you were adjusting, say cylinder 1 to 4, the only reason 2 and 3 change are because the idle speed is changing, pulling more or less in 2 and 3. If at this point, if you try to "fix" 2 or 3 you're only fighting yourself. You need to forget about 2 and 3 until it's their turn. Once you have 1 and 4 equal, re-adjust the idle, recheck equal, repeat until idle is right and 1 and 4 are equal before moving on the the next cylinder, repeat for 2 to 4 and 3 to 4. The fact that 2 and 3 moved while adjusting 1 to 4 means nothing. The only reason they're moving is because the channels are tied together in the manometer.
When I did mine, I did all 3 cylinders (1,2,3, to 4) once. I only went thru the second time to double check my work. When I checked 1 to 4 the second time, after adjusting 2 and 3, it was still perfect. Cylinders 2 to 4 and 3 to 4 where also perfect when I checked them. There may have been some movement "while I wasn't looking" but in the end, they were all equal to 4, therefore they were all equal to each other, the goal.
I've done the starter valve sync using quite a few different methods--a two vacuum gauge tool with in-line restrictors to reduce needle bounce, a Motion Pro mercury filled carb sync tool, and my personal favorite...the Morgan Carbtune tool. And I understand what is being said about syncing cylinders 1, 2, 3 equal to 4, and in theory agree that it should work, but I think the Carbtune is the best sync tool because it doesn't use a common reservoir and each cylinder is attached to it's own port. Using the Carbtune you can see how adjusting one slightly affects the others, but I think the reason for this is because an adjustment of one starter valve changes the "overall balance" of the vacuum system and how much is being pulled thru each the starter valves. And that's what you're trying to do...balance all the starter valves so that each is pulling the same vacuum as #4.