I was out doing a carb sync on my 85 Aspy this morning and it occurred to me that some folks here might just be interested in seeing how I calibrate or "sync" my sync gauges prior to any carb sync.
I use a 4 into 1 manifold I got at Carquest. I don't have a part number but the counter guy was willing to root around back there until he found one. I am pretty sure it 1/4 in.
Then I hook all 4 gauges up to the manifold just as I would to the carbs. This has the added benefit of checking all of the lines etc. Then just pull some vacuum with my Mitevac clone. This is the tool I use for bleeding brakes. Having a vacuum source like this around has many uses in the shop.
Good to go all of the gauges say the same thing. Accuracy of the reading is not important at all. What you are looking for is the same reading on all gauges. I try to check them at about 5, 10 and 15 inches to confirm that they all track closely. Surprisingly these cheap gauges track perfectly.
What would need to be done if they are not the same?
These gauges have a screw on clear plastic cover. If you look closely at the gauges you'll see a shiny screw at about the 7 o'clock position. Unscrew the cover and carefully adjust the pointer with that screw. When I first got them they were really off. When I adjusted all to read the same they all zero'ed at the same place also. Something they did not do when new. It should have been a hint to me, that they all had a different zero reading, but I missed it. FYI I've only calibrated them that one time and they have held for over a year but I do check them every time before hooking them to a bike.
Now if your gauges aren't adjustable just note the difference in reading and adjust all carbs so they read the new "calibrated" reading from your observation. Most motorcycle carbs I've seen pull about 9 or 10 inches at idle so just calibrate your gauges around 10 inches and you should be good to go. Remember the Honda manual considers them in sync if they are all within 1.5 inches of #4 (in the case of the 1200) or #3 with the 1100 I think.
Of course, use the MityVac! I use a similar four port connector to sync the gauges but I did it to a single carb port. I have a vacuum gauge. Why didn't I think of that?? Good tip.
Just wondering what the local shops charge for something like this...my ride is setting while running at 3000 rpms. Could it just be a simple idle adjustment or sync? (sorry new to this)
LonnieD wrote:Just wondering what the local shops charge for something like this...my ride is setting while running at 3000 rpms. Could it just be a simple idle adjustment or sync? (sorry new to this)
First of all welcome to the forums and you did the right thing by asking a question. I have no idea what a local shop would charge for a carb sync. It usually only takes me about 15 to 20 minutes from dragging out the gauges to syncing the carbs if all they need is synced. So figure 1/2 hour shop time. Better yet call them and ask.
Since your bike idles at 3k rpm I'd say at the very least you need the check that the choke is fully off and then adjust down to about 1000 rpm. There is an idle adjustment screw usually located right near where the throttle cables hook to the carb. You can easily identify it because it will be the biggest screw on the carb throttle assemble. Just turn it counter clockwise a bit and stop when the rpm gets down to 1000. Now if that screw doesn't change the idle down I suspect your choke isn't coming full off. Look for kinks in the choke cable and visually look to see that the choke arm, at the carbs, really goes full closed with the choke knob fully pushed in.
I see you are in Seattle and I think there are NGW members close by. Maybe one of them could be talked into helping you out and do it yourself.
JD, I have a set of guages just like yours. My stepfather gave them to me. Can you tell me how you keep the needles from oscillating when you hook the carbs to them? Mine go back and forth so much I cannot determine where the needle is pointing.
If you look at the pics you will see a white plastic valve just below each gauge. You screw those valves down until the needle just barely quivers. you don't want the needle to stop moving as that means it's not reading correctly. But if you get them down so they only quiver about +/- 1/2 inch that will be good.
If yours don't have those valves you can get them at the fish department in department stores or in pet stores that sell fish.
