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  #21  
Old 08-06-2017, 05:43 AM
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Plummit Plummit is online now
 
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Quote:
Originally Posted by Gandalf View Post
Just for fun:





Old school, triple side draft SU carbs, complete with oil pots
I still have a uni-syn from the days i owned a Bug Eye Sprite. It worked very well for adjusting the dual SU carbs.

-Marc
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  #22  
Old 08-06-2017, 06:13 AM
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Originally Posted by AirHound View Post
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 .
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  #23  
Old 08-06-2017, 07:53 AM
AirHound AirHound is offline
 
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Quote:
Originally Posted by tomkk View Post
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?
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  #24  
Old 08-06-2017, 09:57 AM
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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.
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  #25  
Old 08-06-2017, 10:27 AM
E. D. Eliot E. D. Eliot is offline
 
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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:
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  #26  
Old 08-06-2017, 11:44 AM
BillL BillL is offline
 
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Quote:
Originally Posted by E. D. Eliot View Post
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.
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  #27  
Old 08-06-2017, 03:44 PM
Driftdown Driftdown is offline
 
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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!
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  #28  
Old 08-06-2017, 04:10 PM
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Piper J3 Piper J3 is offline
 
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Here's some free videos on the subject...

https://www.youtube.com/watch?v=5wXfiVBO2Uc

https://vimeo.com/68058141
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  #29  
Old 08-06-2017, 06:28 PM
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Quote:
Originally Posted by AirHound View Post
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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Last edited by tomkk : 08-06-2017 at 06:30 PM.
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  #30  
Old 08-06-2017, 09:59 PM
RFSchaller RFSchaller is offline
 
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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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