Vacuum gauge hard to get reading

After cleaning out the carbs this winter I am trying to sync the carbs and I am having a little trouble getting a reading on my vacuum gauge. I am trying to do this the "old school way" as described by Rick however my gauge jumps around so much I can't seem to get a good enough reading to do any tuning. Right now it runs fine except while accelerating. While accelerating (or with multiple people on the bike) it feels like it is miss firing with a muffled thud sound coming out of one side of the exhaust every once and awhile.

I did already have a "baffle" installed in the gauge line as described.

 

i tried the baffle thing too, it didn't work for me either
try making a plug out of paper towel and put it in the hose, i shove it in with the gauge
might take a few tries to get it right, it has to be pretty tight fit

 

I chucked the vac gauge and made the differential bottles in my gallery. The bottles tell you IMMEDIATELY when the carb pair is perfectly matched. Its ideal for our bikes where you have to adjust 3 pairs of carbs to get the synch accomplished.

 

Mine gauge was doing the same thing. i used an old mig gun tip as the small orifice but it was still jumpy. I then added a fuel filter, the basic metal 1/4" filter from NAPA, it was a tight fit onto the tubing, but is made a HUGE difference, the needle moves maybe 1/8" or less.

 

I did some playing around with the gauges last week, and this is what I did:

Using Rick's one-gauge method, I went back and forth between the two carbs on a given bank; I ran the engine up to 2500rpm, to settle the needle down. That got me close. Then I used the manometer to dial it in.

The reason I used the gauge first is because when I hooked the manometer up, the water got sucked into the engine; that told me the two on that bank were way out of whack.

 

I have the restrictor and baffle. It does jump a bit but you just look at the high side (max reading it is jumping too) and set the other carb to it.

Remember exact reading is not the game - balance is. I'm with Schmuckaholic - I think I am going to build a bottle rig and get it close with the gauge and fine tune with the bottle. Or I may just break down and buy the right tool

 

I looked at the options of making various gauges for the sync. Long story short, I reached the point of suspecting that I was going to be doing this a lot (and I have) so I should go ahead and break down now and get the carbtune.

Glad I did. I have sync'd my carbs around 5 or more times during tuning and the carbtune made it pretty easy. Our exchange rate is pretty good, so the price is down now. At today's exchange rate, you can pick one of for $86.

While I don't have anything to compare it to, I can say that the carbtune make the job pretty easy.

 

You can get a set of these and put them inline... That should pretty much take care of the needle jumpiness. You can set them so the needle barely moves or just flutters a bit.

 

Dagnabbit, I was just down at Lowes today. Had I seen this earlier...

 

I have not used the "one gauge" method, but I'd set it up with a 4 gang fish aquarium valve near the carbs, then to a 32 OZ glass bottle, which would absorb the pulses, then to the 1 gauge. Pretty simple.

But I already built a 4 tube Manometer, initially for free, out of hospital oxygen masks and stuff I had laying around. It's a little more work to build, but it's so COOL watching 4 tubes responding to the slightest tweaks, you can even see a level change as you tweak the Pilot screws.
You just can't see that with a 1 gauge, or a 2 bottle, or a 2 tube.

 

I'm seriously considering doing something similar and mounting it to the wall of the shop. Tell the customers I've got the world's most sensitive carburetor synchronizer. Just imagine the stars in their eyes as the columns twitch and their $$ go into my till!

For twitching problems on gauges, some sort of reservoir helps (I suspect the fuel filter in the line provides this). Your restriction needs to be near the engine and your reservoir on the gauge side of it. Could be a bottle, fuel filter or longer piece of hose will do the trick.