Today's Message Index:
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1. 04:12 AM - Re: Rough 912 UL Engine Operation when Pneumatically Balancin (Icrashrc@aol.com)
2. 04:38 AM - re - Rough 912 UL Engine Operation when Pneumatically Balancing Carbs (Peter Thomson)
3. 06:50 AM - Re: re - Rough 912 UL Engine Operation when Pneumatically Balanc (Roger Lee)
4. 09:50 AM - Re: Re: re - Rough 912 UL Engine Operation when Pneumatically Balanc (rparigor@suffolk.lib.ny.us)
5. 03:03 PM - Re: re - Rough 912 UL Engine Operation when Pneumatically (Roger Lee)
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| Subject: | Re: Rough 912 UL Engine Operation when Pneumatically |
Balancin
Check that the idle stops are not interfering with the throttle plate
movement. You're trying to idle the engine pretty slow. Maybe even slower than
is
recommended by Rotax. I think minimum is 1900rpm. I'm sure one of our resident
912 experts can advise you further.
Scott
_www.ill-EagleAviation.com_ (http://www.ill-EagleAviation.com)
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| Subject: | re - Rough 912 UL Engine Operation when Pneumatically |
Balancing Carbs
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
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| Subject: | Re: re - Rough 912 UL Engine Operation when Pneumatically |
Balanc
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.
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 vaccum. The one with the lower vacuum is using more
fuel /richer and the one with the highest vaccum 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
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Service Center
520-574-1080
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=218880#218880
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| Subject: | Re: re - Rough 912 UL Engine Operation when |
Pneumatically Balanc
Hi Roger
"I lean out or throttle back the richest carb to equal the leaner carb.
The one with the lower vacuum is using more fuel /richer and the one with
the highest vaccum is less throttle or leaner"
When you say you are going to lean out the richest carb or throttle back,
is that one thing to do or two things you can do?
If you meant only one thing, that would be closing butterfly a bit.
If you meant two things, it would be:
closing the butterfly a bit
or
perhaps unscrewing the mixture screw a bit to allow more air (or??)?
Thx.
Ron Parigoris
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| Subject: | Re: re - Rough 912 UL Engine Operation when Pneumatically |
Sorry for the misunderstanding. I was just trying to be more clear and I guess
I muddied up the water. Forget I used the word lean out as that usually pertains
to adjusting the jets or needles.
Just move the carb throttle lever or bowden cable so it gets less fuel. The vacuum
guage with the lower vacuum number is getting more fuel (pulling less vacuum).
The vacuum guage with the higher vacuum number is getting less fuel (pulling
a higher vacuum). I usually move the richer carb's bowden cable so it is
getting less fuel and the vacuum guage needle moves to a higher vacuum number
to equal the other carb guage. You can see which one carb to adjust or which way
to move the carb throttle lever by just moving it slightly with your hand and
watching the vacuum guage needle move. If it moves the wrong way then move
it the other way.
Note*
Just make sure your cockpit throttle lever bottoms out to idle at the same time
as the carb idle stop screw bottoms out. If the carb idle stop screw bottoms
out before your throttle lever in the cockpit is all the way back then you may
bend the carb throttle stop by putting too much pressure on it.
Once you have done one or two carb syncs it will be a piece of cake.
If this didn't clear it up let me know.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Service Center
520-574-1080
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=218977#218977
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