dougsnash
Joined: 14 Apr 2008
Posts: 281
|
 Posted: Sat Jun 09, 2012 4:37 am Post subject: RotaxEngines: Rotallxl 912 ULS Mystery |
 |
|
John, is it possible one of your enrichener arms is not coming completely to the closed position after startup? At higher RPM the enrichener acts as a vacuum leak and creates a lean condition. One slightly open enrichener would explain the roughness at higher RPM and excessive mag drop. If it were just on the edge of being closed enough or not it would explain why sometimes your engine runs fine and other not. I had a similar problem during the initial install of my 912 on my CH-701 in that I could not reach full static RPM.
Doug M
CH-701 from scratch
NW Ontario, Canada
Time: 11:42:47 AM PST US
From: "JohnF" <n29cx(at)ridgeviewtel.us (n29cx(at)ridgeviewtel.us)>
Subject: Rotallxl 912 ULS Mystery
After a nice runup last evening; that is, nice mag drops (about 100 on
each side) and static rpm around 5050, and engine running smoothing.
This morning I took the plane out to fly...taxi to end of runway (about
one mile) and did runup with oil temp 125-degrees F. Mag drop 330/360
- very untypical, and running rough. Static impossible to reach. Engine
rpm decreased as throttle advanced past 4050 rpm or so....very
rough...idle way too low...around 800 rpm.
Experienced RV builder and local A&P got involved. We tried all sorts
of things; like removing the air filters...no difference....sometimes,
not always, if top cowling was removed engine ran fine...sometimes not.
Nothing touches the cowl when it is on so nothing is interfering with
the engine due to cowl on or off. Only air flow may be different.
Reseated carbs after looking at the rubber ring they mount on...look
OK..carbs secure. All controls smooth and move stop to stop.
Because engine SOMETIME ran well with top cowling off, we put it on and
taped the oil filler door open to see if increased air flow would make
any difference...it did not.
This is the third time the plane was just fine when put away and no good
the following morning.
Temperatures have been moderate...high 40's at night, low 80's mid day.
Scat cooling from cowl to engine shroud secure and clear.
Pulling electric fuel pump fuse with engine running lowered fuel
pressure slightly but made no difference in poor operation....nor does
it make a difference with the engine is running well.
I am told that the definition of stupidity is doing the same thing over
and over and expecting different results. I seem to be at that point
now.
'Its still one giant mystery of intermittent good/bad operation.
John
[quote][b]
| | - The Matronics RotaxEngines-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RotaxEngines-List |
|
|
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
