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View Full Version : How to make a manometer (carb balancing tool) for under $10



Slavvy
11th September 2011, 21:16
Pretty simple really. First head over to bunnings and get a couple of meters of transparent plastic hose the right diameter for the job (roughly the same size as vacuum hose). It costs 89c a meter but I got overzealous and got about 4m.

Next head to K-mart and get a pair of straw sipper cups for children. They have to be the sort with a suction hole on the lid and a tight fitting straw which goes into the cup.

Take the lids off and fill each cup 2/3rd's of the way with ATF (I used dex3 but I can't imagine it matters) or a similarly viscous fluid. ATF is ideal because it's just thick enough to avoid splashing about, but also very easy to see and thin enough to flow easily through the tubing. I hesitated at using water because it's so runny that the ripple effect from the engine running might suck it into the motor, and then bad things happen :innocent:

Cut a length of the bunnings hose and shove it into either of the lid holes so that it goes down into the fluid in both cups. Cut the remainder of the hose into two big lengths, attaching one to either vent hole on the sipper cups. They have convenient tube bits that stick out seemingly for just such a purpose! I had to use the slightly narrower tubes the cups came with as 'adapters' for the bunnings hose as it is slightly too large to seal.

Hook up either hose to each carbs and you're away. The level will alter depending on which carb is making more vacuum, it transfers very slowly even when the carbs are way out of whack, so there's no danger of the level suddenly rising and being sucked into the carb. With a little thought you could easily apply this to a bike with 4 carbs.

I'm aware that there are already many write-ups of this on the net which are better than mine, but I thought I'd put this up because it verifiably works and is nz-specific for the ingredients. Also costs less than ten bucks :)

Crappy pics, ahoy!

246667246668

Coolz
12th September 2011, 13:15
Great post. Bling sent. My question is how do you attatch it to the carbs? I have found the screw you remove for this purpose.Do you just jam the hose in the hole or is there some attatchment you can buy to screw into the carb?

Slavvy
12th September 2011, 17:18
Great post. Bling sent. My question is how do you attatch it to the carbs? I have found the screw you remove for this purpose.Do you just jam the hose in the hole or is there some attatchment you can buy to screw into the carb?

I'm not sure how your bike is laid out, but mine has a vacuum line linking one carb to the other for whatever reason. I just pulled that off and connected the two hoses in it's place. Alternatively you could use the vacuum hose fittings for the fuel tap if yours is the vacuum activated type.

If all your bike has is threaded holes for the purpose, my suggestion would be to find a pair of brake bleeder nipples with the same thread (autostop sell them), screw them in tight and plug the hoses on the end.

Coolz
14th September 2011, 20:44
I'm not sure how your bike is laid out, but mine has a vacuum line linking one carb to the other for whatever reason. I just pulled that off and connected the two hoses in it's place. Alternatively you could use the vacuum hose fittings for the fuel tap if yours is the vacuum activated type.

If all your bike has is threaded holes for the purpose, my suggestion would be to find a pair of brake bleeder nipples with the same thread (autostop sell them), screw them in tight and plug the hoses on the end.
No vacum hoses on my old girl,will try your suggestion.Thanks for that.

Coolz
15th October 2011, 19:51
Finally got around to building one of these and synced my carbs today.It worked a charm. The bike now pulls much stronger and idles more smoothly,even the exhaust note sounds sweeter.Saved me money too.I can recomend this simple device.248597

darkwolf
15th October 2011, 22:15
Must know more...

I'm off to use my google foo. Would be great to see more info about how you balance the carbs once you see they are not balanced when I return though :)