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peterlthomson(at)gmail.co
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 Posted: Thu Dec 11, 2008 4:38 am Post subject: re - Rough 912 UL Engine Operation when Pneumatically Balanc |
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I just had similar problem.
The video on rotax-owner.com is quite good and you can download it
with Real player v 10.
Left side had 3" higher vacuum than right. Reducing left side resulted
in flooding. Checked float level which was slight higher in left than
right, and reduced it a little to about equal, then increased RIGHT
side cable.
This gave the desired result.
I'll do it again at 50hr intervals as quick and simple process.
Peter
CH701/912ULS
do not archive
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Thu Dec 11, 2008 6:49 am Post subject: Re: re - Rough 912 UL Engine Operation when Pneumatically Ba |
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Hi Hugh,
The engine must be at operating temp to set the carbs or you will have a very hard time setting them. I warm the engine up first then do the mechanical and pneumatic sync.
I use either a set of certified liquid filled guages and needle valves in line to dampen the pulsations or I use a "Syncromate" electronic carb balancer which is ten times more accurate. Either way is fine.
First make sure to carbs are mechanically synced. Make sure the mixture screw on the bottom is 1.5 turns out on each carb. Then use a .004 feeler guage to set the idle stop screw. Then make sure the carbs open and close to the stops with your in cockpit throttle lever. When the throttle is all the way closed make sure each carb does not have any slack in it at the throttle arm on each carb. I usually turn open the idle stop screw about .75 - 1.0 turn open after the feeler guage has been used this usually puts me around 1800 rpm at first start. If your guages are very far off then make sure the guages are equal before use and make sure you have no air leaks in the test hoses.
I chock the wheels and set the brakes. If you don't trust this then tie it down.
Run the engine up to 2800-3000 rpm and use the boden cable for the adjustment. You need to be high enough throttle to be up off the idle stop screw. I lean out or throttle back the richest carb to equal the leaner carb. If you don't have enough adjustment in that one cable then split the difference between the two carbs until they are equal vacuum. The one with the lower vacuum is using more fuel /richer and the one with the highest vacuum is less throttle or leaner. Then go back down to idle and set the idle stop screws so you are at 1800 rpm and the carbs are equal. Use the idle stop screw for this adjustment.
Once both are equal I will run the engine up to 4000 - 4500 rpm to make sure the carbs are really equal at the higher rpms because that is were you run most of the time is the higher rpms. If I need to make a small adjustment then I do. You should now be done just double check the bowden cable nuts and put some thread lock on the two idle screws and reconnect the cross over.
Too many people think the crossover is a cure all, but it only takes care of small difference in any unbalanced situation.
If you have any problems give me a call. Roger 520-574-1080
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| Description: |
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Download |
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Microsoft Word - 912 carb sync.pdf |
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41.32 KB |
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528 Time(s) |
_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
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