Dirt Cheap Manometer

Here is a quick guide on my dirt cheap manometer. Total cost due to having canning supplies around the house was roughly $5.

Required supplies

2 x Mason Quart Jars
2 x lids
2 x jar rings
12 feet of 3/16 ID x 5/16 OD tubing
1 package of art/hobby clay
water
food coloring

Tools

Knife or scissors
Drill and 3/4" bit
Step stool

Steps

Drill two 3/4" holes in each lid.

Cut a 1 foot section of tubing and route it through the lids and rings. You will want the ends of this tube to reach the bottom of the jars.

Cut the remaining tubing in half, this will allow you to move the manometer away from the bike. Route each of the two longer pieces of tubing through the other hole in the lids. These tubes will connect to the vacuum boots on the carbs.

Fill each jar 1/3 of the way full and add a few drops of food coloring.

Screw the rings and lids on to the jars

Use the clay to seal the space around the tubes.

The tube connecting the two jars should reach the bottom of the jar. The tubes running to the carbs should only be inserted 1" or so into the lids. Too far into the lid and you will suck up water.

Picture one shows how far out of sync I was after doing what I thought was a very thorough bench sync.

Picture two was taken 24 hours after syncing, the jars are sealed well enough that the connecting tube is still holding water.

I spent more time waiting in line to buy the tubing than it took to build. Syncing took a bit longer because 99% isn't always close enough for this guy.

Prior to building this, I spent quite a bit of time looking for an explanation as to how it will work. All science aside here is what will happen.

Run the longer tubes to the carb vacuum ports. Pull the caps to access them and be sure to cover the two ports that are not in use. The bike should be at operating temp prior to starting this procedure. The engine will suck the fluid from one jar to the other. I set the jars up to match the cylinder. You should connect them to 3-4, 1-2 then 2-3. Using this example I connected the right jar to cylinder 4 and the left to 3 for the sync of the right carbs. I then connected the right jar to 2 and the left jar to 1 for the left carbs. Finally to sync each side I connected the left to 2 and the right to 3. When you first start the bike, the carb that is pulling stronger will suck the water into it's corresponding jar. My first picture shows how much stronger cylinder 4 was pulling than cylinder 3. I found that I was able to turn my screw driver on the sync screw in the direction of the weaker cylinder until they balanced. If you fully empty a jar, hit the kill switch and the fluid will even out between the jars by siphoning from the full jar to the empty all on it's own.

It was an extremely simple process once I started. Even managed to employ some kid power when my 12 year old thought she was better with clay than I was. The process of syncing ended up being more fun for her than playing on her phone, so I count that as a win.

 

I knew I needed to sync and colortune, but put 250 miles or so on the bike anyway and just pulled the plugs. It just shows things are off and I knew they were, but having too much fun riding!

 

... and "my manometer" (sung to the tune of "My Sharona")


A piece of oak flooring I had left over.. .32" long
A coat-hanger, cut, bent and inserted through holes in one end of the wood. lets me hang it from a handlebar.
20' of 3/16th ID tubing, cut it down once I knew how long I needed it to reach the carbs + some extra.
6 3/8" cable clips.
a good squirt of blue food coloring + some water. Let gravity help the drops find their way down.
Total cost < $8
I can connect this to 2 carbs and if they're balanced, the levels should match. I'll try this out tomorrow.

 

Water has a nasty habit of flashing to steam and bending connecting rods if it gets sucked into running engines.

I'd recommend using automatic transmission fluid instead.

3 and 4 are rich. Synching will not adjust the fuel mixture.

 

I've been running with the choke partially on because it dies at idle. I suspected 1 and 2 were lean instead. I adjusted each 1/4 turn CCW tonight. I really need a colorsync plug now. I should also point out my idle may simply be too low (in addition to 1-2 being leaner than 3-4), but this isn't my debug thread.. I probably should have posted my plug photo elsewhere.

 

I'm currently waiting to get off a late conference call before I test out my "colortune" plug. If it works I will write up a guide for it.

 

They work. What's not in the manual is patience and a fan. You want a fan blowing on the front of the engine so it doesn't overheat and you want patience as it takes a few seconds for a "nickel width" of a turn to register.

 

I'll have to order one. I found a site that claimed you could pull apart a spark plug and use clear epoxy to make your own. 2 different types of epoxy didn't work, guess I shouldn't be trying to reinvent the wheel.

 

I used my manometer tonight. It worked as well as I expected. I was able to sync pretty easily and was never in danger of getting water into the intake. The imbalance was never that large.
It was interesting to see the balance changed when I rev-ed the engine. I'll need to adjust mixture, then re-sync.

 

I found that the adjustment was as touchy as everyone had claimed. A second either direction on the screw can make a change. Fun tool to use with some kids around.