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Carburetor Sync Equipment

Pilotman

I'm New Here
I want to build the test fixture for synchronizing the carburetors. Any suggestions with associated piece part sources would be appreciated.
 
I use the electronic Carb Mate from California Power Systems, but at the ROTAX course the instructor had a neat setup using a manifold pressure gage from a twin engine aircraft. He just adjusted the carbs to get the gage needles on top of each other.
 
Two for the Carbmate. Keith drop me an email. I'm over at 16X west of Justin TX. I'd be happy to hook up and help you do the carb synch. John

Check out the videos here:
http://rotax-owner.com/en/
 
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Simple synchronizer

Remember the old days when we had MGB's and Honda 750's with four carbs? We used a manometer stick made with cheap Tygon and plastic or glass tubing.
 
I was taught in school that the Carbmate and Syncromate were okay, but you an not diagnose with them and it is much harder to pick a carb you want to adjust. The analog gauge setup tells you which carb to adjust and by about how far. It can tell you if the ideal circuit is obstructed or if the carbs are so far out you need to adjust the cable length on the throttle arm. The electronic sync instruments can split a hair, but once you disconnect it and hook the carbs back up all the hair splitting is gone. Gauges are just so much faster.
 
I was taught in school that the Carbmate and Syncromate were okay, but you an not diagnose with them and it is much harder to pick a carb you want to adjust. The analog gauge setup tells you which carb to adjust and by about how far. It can tell you if the ideal circuit is obstructed or if the carbs are so far out you need to adjust the cable length on the throttle arm. The electronic sync instruments can split a hair, but once you disconnect it and hook the carbs back up all the hair splitting is gone. Gauges are just so much faster.

I agree for all the reasons mentioned.
In our shop we use the two column version of this.
http://www.carbtune.com
 
Joe, if you have the mechanical synch correct the Carb Mate should work fine. My engine runs really smooth at and idle of 1800.

Rich
 
I bought a twin engine manifold pressure gauge on eBay. They show the use of one of these on the Rotax Owner website. :)
 
Best

Two for the plastic and bottle solution: I build a gauge of two bottels and some hoses that worked great! Just functie the cards until the two bottles contain equal amounts of water. Fun to make and I loved to work with it. Google on carb's and synchronisation.
Spend the money to something that will give you advantage.
 
Need to learn how to use carbmate. ROAN videos don't explain what side to adjust

:confused:
I use the electronic Carb Mate from California Power Systems, but at the ROTAX course the instructor had a neat setup using a manifold pressure gage from a twin engine aircraft. He just adjusted the carbs to get the gage needles on top of each other.
 
:Need to learn how to use carbmate. ROAN videos don't explain what side to adjust

Doug ... when using the CarbMate one carb becomes the "reference" and the other carb is adjusted to match it. It really does not matter which carb is the reference as long as the other carb is adjusted to match the vacuum of the reference carb at idle and the high RPM range .... and, of course, the final idle speed should be within the desired specs. When the center light is on and you are on the high sensitivity setting, the carbs will truly be balanced to each other.

A tool like the CarbMate is just fine for synchronizing the carbs, however, the bad thing about using a device like the CarbMate is it is not well suited for trouble shooting because one really does not know what the actual vacuum levels are. If everything is OK with the engine & carbs and all you are doing is synchronizing them, then using a device like the CarbMate is just fine ... however, if you are having issues, it does not lend itself well for troubleshooting problems. This is one reason why I have both the CarbMate and gauges.

About the gauges, if one is inclined to order a pair ... don't make the same mistake I did when asleep at the wheel late one night clicking away ordering two vacuum gauges that were "0-30 inches of water" gauges. The inches of water gauges I accidentally ordered were DESTROYED a few seconds after the engine started .... an expensive mistake. Make sure the gauges are 0-30 inches of mercury and NOT inches of water. I can laugh about it now, but it was NOT funny at the time.
 
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Doug ... when using the CarbMate one carb becomes the "reference" and the other carb is adjusted to match it. It really does not matter which carb is the reference as long as the other carb is adjusted to match the vacuum of the reference carb at idle and the high RPM range .... and, of course, the final idle speed should be within the desired specs. When the center light is on and you are on the high sensitivity setting, the carbs will truly be balanced to each other.

A tool like the CarbMate is just fine for synchronizing the carbs, however, the bad thing about using a device like the CarbMate is it is not well suited for trouble shooting because one really does not know what the actual vacuum levels are. If everything is OK with the engine & carbs and all you are doing is synchronizing them, then using a device like the CarbMate is just fine ... however, if you are having issues, it does not lend itself well for troubleshooting problems. This is one reason why I have both the CarbMate and gauges.

About the gauges, if one is inclined to order a pair ... don't make the same mistake I did when asleep at the wheel late one night clicking away ordering two vacuum gauges that were "0-30 inches of water" gauges. The inches of water gauges I accidentally ordered were DESTROYED a few seconds after the engine started .... an expensive mistake. Make sure the gauges are 0-30 inches of mercury and NOT inches of water. I can laugh about it now, but it was NOT funny at the time.

John-G, thank you! Here's my read back. Do the mechanical sync procedure first, then for the pneumatic procedure pick a side as REF and make all carb cable adjustments on just the opposite side in whatever direction that moves the red dot to the green in the center. Do this procedure for 2000, 3000, 4000 and at each RPM level make adjustments on each charbmate setting down to .05?
Am I close? Oh and then once Nurvana is achieved make final idle stop adjustments. ?
 
Doug - You have the general idea ....

I would suggest trying to first get an idle speed that is in the ballpark using Van's suggested idle speed range. Moving forward, while adjusting the non-reference carb, should the idle RPM go up or down tweak the idle accordingly then verify the carbs are still in sync at the idle speed you've chosen. You will find yourself going back and forth a few times. After you get the carbs close at idle, continue to the off idle synchronization.

For the high RPM I have read here and elsewhere that a little higher RPM than the 3,000 you mentioned is better for the off-idle adjustment because it insures the carbs are out of the idle circuit ... think I used 3,900 RPM which seems to have worked well. When you think about it this engine will typically either be operating at 1,800 to 2,100 when on the ground or well above 4,000 RPM in the air.
 
I use a Carbmate. I just suck on one of the sensor hoses each time to see which way the lights go and use the fact that the high suction side is the low load side.
 
Doug - You have the general idea ....

I would suggest trying to first get an idle speed that is in the ballpark using Van's suggested idle speed range. Moving forward, while adjusting the non-reference carb, should the idle RPM go up or down tweak the idle accordingly then verify the carbs are still in sync at the idle speed you've chosen. You will find yourself going back and forth a few times. After you get the carbs close at idle, continue to the off idle synchronization.

For the high RPM I have read here and elsewhere that a little higher RPM than the 3,000 you mentioned is better for the off-idle adjustment because it insures the carbs are out of the idle circuit ... think I used 3,900 RPM which seems to have worked well. When you think about it this engine will typically either be operating at 1,800 to 2,100 when on the ground or well above 4,000 RPM in the air.
Ok! Sounds to me, once center green/idle is lit up and let's just say 1800, then go 3800 but am I correct about making adjustments only on the nonREF side and doing them in each of carbmates 3 settings? Don't mean to nail it down here just looking for a proven jumping off point and the how. It's amazing how little there really is out there on the the web that goes into detail. I do believe it's easy as many say, but there's unwritten method to the madness for carbmate too. Sure wis others would pipe up to clue me in too. Thanks John G I'll take all with a grain of salt and get some experience. V/r Doug
 
I use a Carbmate. I just suck on one of the sensor hoses each time to see which way the lights go and use the fact that the high suction side is the low load side.

Hey Rich, high suction and low load side, what then, ? Make cable adjustments on that side only? Thank you!
 
Just for fun:

IMGP9891.JPG


uni-syn.jpg


Old school, triple side draft SU carbs, complete with oil pots :)
 
Hey Rich, high suction and low load side, what then, ? Make cable adjustments on that side only? Thank you!

I also use a Carbmate. Granted, the gauges give more info to an expert but I'm not one of those and the Carbmate is very easy for me to use.

I decide which which carb to adjust based on whether I want to ooch the idle RPM up or down. It doesn't matter which one is adjusted to achieve the balance.

Early on I experimented with the Carbmate to see how many "flats" on the adjustment nut it took to move one light on the Carbmate at the two ends of the Carbmate adjustment range. Stuck some masking tape on the Carbmate with those notes. Now if I'm off two lights I know approx. how much to adjust the stop nuts right off the bat.

If I remember right, I check the balance at about 3000 RPM then run the throttle up and down through the full range to make sure they're reasonably balanced throughout. There's usually a small amount of balance drift through the range .
 
I also use a Carbmate. Granted, the gauges give more info to an expert but I'm not one of those and the Carbmate is very easy for me to use.

I decide which which carb to adjust based on whether I want to ooch the idle RPM up or down. It doesn't matter which one is adjusted to achieve the balance.

Early on I experimented with the Carbmate to see how many "flats" on the adjustment nut it took to move one light on the Carbmate at the two ends of the Carbmate adjustment range. Stuck some masking tape on the Carbmate with those notes. Now if I'm off two lights I know approx. how much to adjust the stop nuts right off the bat.

If I remember right, I check the balance at about 3000 RPM then run the throttle up and down through the full range to make sure they're reasonably balanced throughout. There's usually a small amount of balance drift through the range .

Tom would that be flats on the idle stop screw?
 
I think I have a Uni-Syn buried somewhere in the garage from the time I owned a Corvair (affectionately known as the "The Mosquito Fogger". While it would probably work for the RV-12, I like the Carb-Mate better, I think.

I have to stop for a few minutes and figure out exactly what I need to do every time I pull out the Carb-Mate. I bought mine used, with no instructions other than what's printed on the front. I do the idle balance adjustment, then set the idle speed and re-balance to make sure I didn't mess it up. Then I check/adjust balance at 3000 and 4000. The biggest challenge I've run into has been air leaks in the tubing connections.
 
Crude?

I have owned several 1600 VW type autos. While in college, I didn't have the resources go buy a carb balancer. To get a 'carb balance', I stuck one end of a 3' long 1/4" plastic fuel line into each carb one at a time, put the other end of the tube into my ear and listened to the 'sizzle' of the fuel passing thru the carb. Compared and balanced the 'sizzle' sound out between the two carb. I learned how much 'sizzle' produced the best acceleration and called it good. Worked well enough for me to have good performance and fuel mileage. Didn't need no fancy Carbmate or carb balancing tool. cool:
 
I have owned several 1600 VW type autos. While in college, I didn't have the resources go buy a carb balancer. To get a 'carb balance', I stuck one end of a 3' long 1/4" plastic fuel line into each carb one at a time, put the other end of the tube into my ear and listened to the 'sizzle' of the fuel passing thru the carb. Compared and balanced the 'sizzle' sound out between the two carb. I learned how much 'sizzle' produced the best acceleration and called it good. Worked well enough for me to have good performance and fuel mileage. Didn't need no fancy Carbmate or carb balancing tool. cool:

It works, but the VW's weren't quite the challenge as the side draft CV carbs and Webers. I have a Uni-Syn too (real good for CV carbs), along with 4 vacuum gauges and adapter tubes for mikuni's. The latter is a ultra cheap tool that could be replicated with a couple of vacuum gages from HF. Just tie a knot in the hose and tighten for reducing the intake pulses. Works very well and adjustable too ;). Tuned dozens of 4 carb Honda 500, 750, and Kaw 4 strokes with these. Just test the gages and mark the calibration offset between them as they probably won't read the same.
 
I am sure most owners know about this, but for the benefit of those that don't, there is a good video on Rotax Carburetor Synchronization. It walks you through the whole carb sync routine, starting with mechanical synchronization and ending with the pneumatic synchronization. I highly recommend it.

To view all the Rotax educational videos, you must be a member. I believe it is still $30/year. In my opinion, well worth it. You will also get notifications of the latest service bulletins and new video releases. It has taught me a lot over the last 3 years. Still learning here!
 
Tom would that be flats on the idle stop screw?

No, I'm referring to the flats on the hex nuts on the throttle cables. The throttle cables come in through that brass fitting with the two stop nuts. Adjusting those nuts move the cables slightly in and out to do the synch.

[Edit] The top video above shows it better ...

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When I adjust my carbs I look at the idle speed. If it's high I screw the high load side idle stop in. I only adjust both carbs if needed to get the desired idle RPM.
 
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