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Carb balancing device?


FastEddieB

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I suppose I could ask Roger directly*, but I thought this might be of general interest.

 

My carbs are going out to him in a month or two for rebuild. Obviously I will need to balance them when they go back on.

 

What is seen to be the best device to balance them, and what's the best source, price wise?

 

Thanks!

 

 

*I think I may have in the past, but I'm not remembering the answer right now.

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Hi Eddie,

Here is a link to an earlier post by the safety officer. He has a picture of a simple cost effective setup.

I prefer gauges because they are not only a lot faster, but you can see which carb to adjust, by how far it is off and how much to adjust it, if it is adjustable with the set screw or bowden cable adjuster or does the cable need to be shortened or is there an obstructed carb. The gauge setup cost is far less. Using the electronic one which I do own, but don't use because I can't do any of the things I listed above and you need to hook up the electronic one to a 12V power source.

 

 

http://ctflier.com/index.php?/topic/2532-carb-sync-in-simple-terms/

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Cool!

 

Looks like that setup could save me a bunch of money.

 

Could you describe the gauges you used and where you sourced them? The rest of the hardware looks like a simple trip to Home Depot.

 

BTW, I have a 4-gang MotionPro I could use, but it would need mercury and people seem to be getting nervous having it around.

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Just buy 2 liquid filled 2" gauges from any source. The rest is a trip to Ace Aviation. The gauges are about $30-$40 each and everything else is about $15. make sure you put a needle valve in line on each hose so you can restrict the vacuum pulsation and make the needles rock steady.

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  • 3 weeks later...

OK - I need to start my annual shortly (expires the end of this month).

 

The only other tool I think I should have is a differential compression tester.

 

Is something like this good enough, and are there any other accessories needed (I have a compressor already).

 

http://www.aircraftspruce.com/pages/ep/test/diffpress12mm.php

 

Thanks!

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Thanks.

 

I just went to YouTube to start reviewing both the carb balance and compression videos.

 

They show samples, which lead you to RotaxOwner.com for the full videos.

 

For a full membership over there, its $29.95/year.

 

Is this a no-brainer for a ROTAX owner? Sounds reasonable enough.

 

Thanks.

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Rotech is a B.C Canadian company and is the main distributor for Rotax in Canada. They own the Rotax-Owners forum, I'm just an admin. They handle most if not all the 912S certified engine's and parts in Canada and the US. This is where the US distributors get their certified parts. The Dog here on our forum writes their tech articles.

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  • 3 weeks later...

1) After several failed attempts, I finally got signed up for ROTAX-Owner.com (with Karen's help!)

 

2) I got the gauges last week and just unpacked them yesterday.

 

Problem:

 

They are not synched with each other:

 

13146041023_342c96d776.jpg

 

I got the lens off of the one on the right, thinking either the phillips or slot-headed screw might be for zeroing, but neither turns easily.

 

I will call Aircraft Spruce when they open, but any ideas?

 

3) Should I go ahead and install the inline valves to damp out oscillations, or try it first without? Right now I'm just a few days away from getting my carbs back from Roger, so I want to be ready.

 

Thanks, and hope this is helpful to others as well.

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Regarding calibration of gauges, I would connect them to a common source of vacuum, preferably one that you can control (e.g., a syringe or other device), with a "T" fitting or other connection.  Then I would slowly pull vacuum and see if the gauges show the same values over some reasonable range. 

 

Really, even if they did read the same at no vacuum, you don't know if they remain in calibration across their entire range.  So, doing a calibration of this kind is useful even if they did read the exact same values when open to the atmosphere. 

 

Once you do that, you can decide if you want to establish a user correction (offset of one gauge versus the other) or if you want to get gauges that are a perfect match.

 

As usual, I am not a mechanic and my comments are for the purpose of discussion only and should not be used to guide airplane maintenance.

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FastEddieB: if they remain the same distance from each other throughout the gauge, it is a needle error. You just need to add/subtrack readings. If the spacing changes, there's a bad bourdon tube and you need to return the bad one. Would need a third gauge to find out which is bad.

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I hooked both together with a "T" and did a carefully calibrated "suck test".

 

Error stays the same, so it's a needle error.

 

Does not seem like something I should have to constantly adjust for.

 

Interestingly, if you go to CPS, the gauges in their image are off by almost exactly the same amount - and the photo is flipped 180°!

 

15-05098.jpg

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  • 4 weeks later...

I realized I left this hanging.

 

I got permission to return the gauges to CPS for refund.

 

I bought two similar gauges at O'Reilly's for about $27 each.

 

Mounted them on a small tackle box and managed to hook them up to the disconnected crossover ends:

 

13692239903_2a57953afc.jpg

 

Roger ridiculed me about the "C-Clamp damper valves", so I used the ones in the CPS kit this once.

 

In any case, after the mechanical synch the gauges were very close at 3,500 rpm, off maybe 1/2":

 

13692241943_36570632cb.jpg.

 

I needed more suction on the left gauge (my right carb), so I screwed in the adjusting ferrule about 1/2 turn and on rechecking the gauges aligned perfectly.

 

Then, at idle, two 1/8 turns in on one side (I forget which) to raise the idle and bring the idle readings into agreement.

 

So, not that hard. Went for out first cross-country Saturday and Karen and I both thought the engine felt marginally smoother. Also seemed a tad more powerful, but that could easily be psychological. 

 

In any case, its highly rewarding to learn a new skill and to have it work out so well.

 

Finally, the compressions on my #3 were a bit low: #1 80/76 - #2 80/76 - #3 80/69 - #4 80/74.

 

Checking them a second time showed maybe 80/70, but no more.

 

To what extent should I be concerned, and should I just recheck them after 10 hours or so?

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