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1. 12:58 PM - Re: CarbMate (Roger Lee)
2. 08:07 PM - Carb sync for beginners (Roger Lee)
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Hi John,
No special brad. I don't buy top dollar, but don't buy cheap either. When you get
them just pull a vacuum on them at the same time and make sure they are reading
the same.
Put an in line needle valve in each vacuum line to pinch it down to dampen the
impulses even more. You can buy every thing you need except the gauges at Ace
Aviation (Ace Hardware). :)
here is a picture of a simple carb sync tool that works very well and doesn't cost
a lot.
I have ab Aces dynamic prop balancer. It is fairly pricey for a one time owner
unless you plan on doing a lot of planes. Wouldn't it be cheaper ($300) to just
pay someone a one time fee.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center - Heavy Maint. Rated
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=416392#416392
Attachments:
http://forums.matronics.com//files/carb_sync_150_483.jpg
Message 2
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| Subject: | Carb sync for beginners |
PROCEDURES FOR MECHANICAL AND PNEUMATIC SYNCHRONIZATION OF THE 912 CARB'S:
This will get you through the basics and after you do a sync or two it will get
easier and you will get better. This is not an official document and is only
meant for your edification and will get you through a carb sync. Some experienced
people that do carb syncs on a 912s may vary some, but the basics ideas are
the same.
Mechanical Synch of the Carburetors Do this First
Bowden cables adjustment screws (cable housing adjuster) should be centered, but
not mandatory. By having the Bowden cable adjustments in the middle of their
adjustment range will give you a little more adjustment when you get to that
part of the procedure.
Adjust throttle cables so that both carb throttle arms move simultaneously to both
extremes (open and closed).
Ensure Idle Mixture Control Screw is properly set (on the bottom of each carb).
Screw them all the way in then back out 1 turns.
Reverse the throttle arm springs so they pull toward closed throttle just to facilitate
mechanical sync.
Unscrew the Idle Stop Screw. Make sure the throttle is closed in the cockpit. With
a .004 feeler gauge between the screw and the arm tighten the screw until
it just touches. There should be minimal friction on the feeler gauge.
Remove the feeler gauge and screw the Idle Stop Screw in 1 turn.
Return springs to original configuration (i.e., pulling the throttle arms toward
to the open position).
Connect the Pneumatic Synch Tool
It is imperative to have the engine up to the operating temperature. Remove one
end of the rubber crossover compensating tube between the two intake manifolds
or connect to the top of the intake manifolds or use the cross over tube rubber
hose pinch off method shown in Rotax owner videos. All these attachment methods
will work.
Hook up gauges or electronic sync tool. Secure one end of a gauge or electronic
device to the rubber end of the compensating tube and the other to the gauge
at the 90 degree fitting coming out of the intake manifold where the compensating
tube hose was removed. Secure both attachments with a hose clamps to prevent
leaks. Leaks will affect the results of your sync process. You can hook up
your sync tool at the small screw on top of the intake manifold, but then you
have to pinch off the rubber hose between the carbs on the cross over compensating
line. I find this is just more work and you need to make sure the rubber
hose on the compensating tubes are long enough (usually newer engines) and you
dont allow any leaks between the carbs. Many people have to cut the tube shorter
and make the rubber hose longer to pinch it if you have an older engine with
short rubber connecting tubes. I think it is easier and faster by just pulling
the hose off as originally described and it facilitates complete carb separation.
Make sure you have good brakes, use wheel chocks and or if you have not so good
brakes or no wheel chocks then tie your plane down and always have someone in
the cockpit. Never do this alone while running an engine and no one in the cockpit..
On Idle Synch
NOTE* Many people like to do the high rpm or off idle adjustment first and
then do the idle set.
I would do the high rpm sync first because it will affect the idle sync.
Note*
The gauge or carb with the lower vacuum number is getting more air/fuel and the
gauge or carb with the higher vacuum number is getting less air/fuel.
Bring the cockpit throttle lever to idle stop. Ideal idle RPM is approximately
1700-1800 rpm depending on your specific aircraft and needs. Adjust idle setting
to this value. The 912UL 80 HP can handle a little lower idle rpm over the
912ULS 100 HP due to compression ratio.
If the idle is high (say, 1900), adjust the carb with the lower vacuum number on
the gauge because that is the one getting more air/fuel. Retard the Idle Set
Screw until the vacuum numbers are the same. Example: If one gauge is at 15
of vacuum and one at 14 of vacuum retard the lower 14 until it drops to 15 to
equal the other carb which will now lower your idle rpm.
If idle is low (say, 1600), adjust the carb with the higher value, it is getting
less air/fuel. Advance the Idle Set Screw until the vacuum readings are the
same. Example: If one carb is at 15 and one at 14 turn the idle stop screw in
on the carb with 15 of vacuum to match the one with 14. This will raise the overall
idle rpm.
Needles should now match.
Off Idle or high rpm Synch
If while running the engine the gauge needles shake then you will need to install
or close down the inline needle valves until the gauge needles stop shaking
and pulsating. Now the needles will likely show different vacuum readings. Do
this sync before the idle sync because this sync usually will affect your idle
sync set point.
Run engine at approximately 3500 RPM. Do the Off Idle synchronizations at this
rpm. I prefer 3500 rpm to start since that is closer to where you run the engine.
You may find that setting the balance at lower rpms doesnt stay very accurate
and that as you move up in rpm to 4000-4500 rpm they are out of sync again.
Set them at the higher rpm or at least double check the higher rpm when you
think you are done. There is a good chance they wont be in sync if you used a
low (
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center - Heavy Maint. Rated
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=416396#416396
Attachments:
http://forums.matronics.com//files/carb_sync_150_818.jpg
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