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Homemade Manometer


Darth Bling

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I built one of these this weekend, to do the carbs on a Goldwing. It looks really nice...but the actual use was puzzleing. I thought maybe someone has an idea of why it didn't work.

On the goldwing you have to have a special adapter that screws into the intake runner, close to the head. I used a 5mm bolt that I drilled the center out of, then cut the head off. A 5mm locknut in the middle worked for screwing it in and out. I used a small piece of tubing to go from my 1/4" id tube down to the 5mm bolts.

I used power steering fluid first (it was what I had) then changed it to ATF afterwards(better color). I hooked all 4 tubes up, 1 to each cylinder, after warming the bike up a bit.

When I fired the bike up, the readings were all over the board...2 cylinders shot up, then air bubbles started forming in them and small amounts of fluid began making their way to the cylinders. I shut the bike down and thought a bit...and couldn't figure it out. I even tried connecting just 2 cylinders at a time(and connecting the other 2 together) but I couldn't get it to balance...it would just go fast to one cylinder.

The only thing I can think of is that maybe I have a leak on my homemade adapters, and thus I get more fluctuations than normal? I noticed the adapters got hot, and the tubes didn't have as tight a seal as before.

I have used a mercury one before, but on a different bike, with no troubles. I am nervous to use this one to do the starter synch if it isn't going to work right...i don't want to mess my VFR up.

Any ideas? I will post pictures, it is a clean looking setup for sure!

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  • Member Contributer
I built one of these this weekend, to do the carbs on a Goldwing. It looks really nice...but the actual use was puzzleing. I thought maybe someone has an idea of why it didn't work.

On the goldwing you have to have a special adapter that screws into the intake runner, close to the head. I used a 5mm bolt that I drilled the center out of, then cut the head off. A 5mm locknut in the middle worked for screwing it in and out. I used a small piece of tubing to go from my 1/4" id tube down to the 5mm bolts.

I used power steering fluid first (it was what I had) then changed it to ATF afterwards(better color). I hooked all 4 tubes up, 1 to each cylinder, after warming the bike up a bit.

When I fired the bike up, the readings were all over the board...2 cylinders shot up, then air bubbles started forming in them and small amounts of fluid began making their way to the cylinders. I shut the bike down and thought a bit...and couldn't figure it out. I even tried connecting just 2 cylinders at a time(and connecting the other 2 together) but I couldn't get it to balance...it would just go fast to one cylinder.

The only thing I can think of is that maybe I have a leak on my homemade adapters, and thus I get more fluctuations than normal? I noticed the adapters got hot, and the tubes didn't have as tight a seal as before.

I have used a mercury one before, but on a different bike, with no troubles. I am nervous to use this one to do the starter synch if it isn't going to work right...i don't want to mess my VFR up.

Any ideas? I will post pictures, it is a clean looking setup for sure!

You might try swapping the hoses around and see if the same cylinder pulls the AFT high into the tubes. If that is the case, it's just the carbs are REALLY far out of sync.

If you have a leak in the adapters I would think that you would have a low reading, not high. Since you are reading vaccum it should pull outside air from the lead which would show the low reading.

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This is a differential manometer meaning that it responds to the difference in vacuum between the 4 cylinders. If you had 2 connections with leaks, the other 2 of the cylinders would read very high and try to suck the fluid in. You cannot connect only 2 for the same reason. Mercury manometers are absolute manometers, meaning that they respond individually to each cylinder's absolute vacuum, so a leak in 1 will not make another read too high.

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Guest Chief Nobody

Whew... I thought a Man-o-meter was some kind of test where you had to engage in :beer: stunts to prove your manhood. The more :goofy: the more manly you are?

:goofy:

Edited by Chief Nobody
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  • 10 months later...

Great stuff, I'll be putting this tool together this weekend. Is there a full writeup on the disassembly of airbox, or is the service manual good enough? Should the tank be taken off entierly?

Regards,

Bruckner

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Great stuff, I'll be putting this tool together this weekend. Is there a full writeup on the disassembly of airbox, or is the service manual good enough? Should the tank be taken off entierly?

Regards,

Bruckner

There's no need to remove the tank completely. Just have to prop it up.

Taking the air box off the bike is pretty straight-forward. The only hard part is getting the MAP sensor unpluged underneath the airbox.

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  • 2 years later...
  • Member Contributer

Each of the four plastic tubes are connect to the vacuum lines from each cylinder. Each cylinder will exert a force on the oil in each tube. Essentially, the cylinders are playing a game of tug-o-war. Whichever cylinder is creating the most pressure will "win" and pull the oil in it's tube higher than the other cylinders. Our goal is to balance the starter valves so each cylinder is exerting the same amount of force, and therefore getting the oil level in each tube to be the same.

Thank You! :fing02:

I'm going to bulid a 4-column mercury vacuum meter and last doubt about was " i need a direct communication with open air or not, more than the four connections to the throttle body ?".

Your project answered to this question.

Ciao, Luigi.

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