Rotax 447 RPMs Climb - Wont Idle Normally

[Aaron Jacobson]

Hello everyone,
A friend of mine built an ultralight from scratch. He's never flown it
unfortunately due to an engine problem with his 447. When he starts
the engine (which presumably starts fine), the RPM's climb up until he
has to shut it off. It will not idle normally. He's been told that
there is an air leak (?) somewhere, but cannot seem to find the
problem. I believe this engine was brand new when he purchased it.

If you have any leads or advice, he would appreciate it very much.
Unfortunately I don't have anymore details than that as I'm just his
messenger and am not a mechanic of any sort.

Thanks in advance.

[Jan Nademlejnsky]

The engine RPM is controlled by carburetor or load. Because the engine is not loaded than the problem must be carb. Borrow another carburetor and try it.

Jan

Post by Aaron Jacobson
Hello everyone,
A friend of mine built an ultralight from scratch. He's never flown it
unfortunately due to an engine problem with his 447. When he starts
the engine (which presumably starts fine), the RPM's climb up until he
has to shut it off. It will not idle normally. He's been told that
there is an air leak (?) somewhere, but cannot seem to find the
problem. I believe this engine was brand new when he purchased it.
If you have any leads or advice, he would appreciate it very much.
Unfortunately I don't have anymore details than that as I'm just his
messenger and am not a mechanic of any sort.
Thanks in advance.

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[Terry]

1st ... Take the air filter off and check to be sure slide is not
"creeping" up from the idle position while running. While the air
filter is off check to see if the slide is moving freely as it should
while moving the throttle control.

2nd... Make sure it has a good exhaust system on it with no leaks and
correct baffles and good gaskets! 2 stroke engines rely on a certain
amount of "back pressure" in the exhaust. If you don't believe me,
take the exhaust system off a 2 stroke engine and watch the rpm's
climb until something breaks. Make sure it is the correct exhaust
system for that engine and again, no leaks.

Hope this helps...

Terry... Flightstar Spyder
Cessna 150G N6401F

Post by Aaron Jacobson
Hello everyone,
A friend of mine built an ultralight from scratch. He's never flown it
unfortunately due to an engine problem with his 447. When he starts
the engine (which presumably starts fine), the RPM's climb up until he
has to shut it off. It will not idle normally. He's been told that
there is an air leak (?) somewhere, but cannot seem to find the
problem. I believe this engine was brand new when he purchased it.
If you have any leads or advice, he would appreciate it very much.
Unfortunately I don't have anymore details than that as I'm just his
messenger and am not a mechanic of any sort.
Thanks in advance.

[d***@epix.net]

Maybe a silly question but . Does he have a prop on it ? Dave

Post by Aaron Jacobson
Hello everyone,
A friend of mine built an ultralight from scratch. He's never flown it
unfortunately due to an engine problem with his 447. When he starts
the engine (which presumably starts fine), the RPM's climb up until he
has to shut it off. It will not idle normally. He's been told that
there is an air leak (?) somewhere, but cannot seem to find the
problem. I believe this engine was brand new when he purchased it.
If you have any leads or advice, he would appreciate it very much.
Unfortunately I don't have anymore details than that as I'm just his
messenger and am not a mechanic of any sort.
Thanks in advance.

[Percival L Mincer]

Actually, Terry, you aren't even close. The exhaust stetem of a two
stroke engine acts as a valve via returning pulses and a boost system.
In fact, most two stroke engines will barely run much less gain speed
without an exhaust, " until something breaks".

Post by d***@epix.net
Maybe a silly question but . Does he have a prop on it ? Dave

Post by Aaron Jacobson
Hello everyone,
A friend of mine built an ultralight from scratch. He's never flown it
unfortunately due to an engine problem with his 447. When he starts
the engine (which presumably starts fine), the RPM's climb up until he
has to shut it off. It will not idle normally. He's been told that
there is an air leak (?) somewhere, but cannot seem to find the
problem. I believe this engine was brand new when he purchased it.
If you have any leads or advice, he would appreciate it very much.
Unfortunately I don't have anymore details than that as I'm just his
messenger and am not a mechanic of any sort.
Thanks in advance.

[Frank]

Post by Aaron Jacobson
Hello everyone,
A friend of mine built an ultralight from scratch. He's never flown it
unfortunately due to an engine problem with his 447. When he starts
the engine (which presumably starts fine), the RPM's climb up until he
has to shut it off. It will not idle normally. He's been told that
there is an air leak (?) somewhere, but cannot seem to find the
problem. I believe this engine was brand new when he purchased it.
If you have any leads or advice, he would appreciate it very much.
Unfortunately I don't have anymore details than that as I'm just his
messenger and am not a mechanic of any sort.
Thanks in advance.

I've seen this a couple of times, it was in each case the slide in the carb
which was held off it's seat. Once the slide had been inserted backward (I
don't know if you can do this with a Bing.) and the other time there was
some other reason it was held off, maybe the idle screw was fully seated, I
don't recall. IN any case the slide must be almost fully down on the bottom
of the carb. It also sounds like you really don't understand what you are
doing, no insult intended, but you really ought to get help. Someone who
will not only help with the problem but can explain and teach you how it
works will be a great help.

[T***@gmail.com]

Aeron,

If the carburettor is mechanically all right, that is if the throttle
slide is moving freely to its lowermost position, you most likely have
an air leak problem. This air leak is located either in the
carburettor, or between the carburettor and the motor, or in the motor
itself (not before the carb or after the motor).
Guide you attention to following items:

Carburettor
Is the throttle cable length appropriate?
Is the idle adjustment screw unscrewed?
Carburettor air screw - Is it unscrewed about 1,5 turns (0,5 - 2,5)?
Carburettor air screw - Is the little O-ring attached properly?
Primer inlet (carb throat) - If there is one and it's not in use, is
it plugged?
Throttle cable inlet - Is it sealed with a rubber cap?
Throttle cable cap - Is the O-ring attached properly?
(Is there a pilot jet properly installed in the carb?)

Carb/Motor
Is the rubber socket between the carb and the motors intake manifold
attached properly and without any air leaks?
Are there any cracks in the rubber?
Are the rubber ring (single carb) and the gaskets for the intake
manifold leaking?

Motor
Is the power inlet/outlet for the fuel pump in use, check line to the
fuel pump, if not - is it plugged?

Are the crankshaft seals, the crankcase half's or the cylinder gaskets
leaking? Confirm with a vacuum leak test. (Less likely on a new motor)


Hope this helps
/Toby

[Jarhead]

"Aaron Jacobson" <***@gmail.com> wrote in message news:***@l12g2000cwl.googlegroups.com...
| Hello everyone,
| A friend of mine built an ultralight from scratch. He's never flown it
| unfortunately due to an engine problem with his 447. When he starts
| the engine (which presumably starts fine), the RPM's climb up until he
| has to shut it off. It will not idle normally. He's been told that
| there is an air leak (?) somewhere, but cannot seem to find the
| problem. I believe this engine was brand new when he purchased it.
|
| If you have any leads or advice, he would appreciate it very much.
| Unfortunately I don't have anymore details than that as I'm just his
| messenger and am not a mechanic of any sort.
|
| Thanks in advance.
|

A trick we used with VW engines was to spray WD-40 around the rubber
intake manifold couplings and around the carburetor. (While the engine
is running) If there is a leak where you spray the WD-40 it will either
temporarily seal it or the WD-40 will be ingested. In the first case the
rpm will decrease. In the second case the rpm will momentarily surge.
What you are looking for is an abrupt change.

[Eagle]

Do you have a prop mounted on the engine? You can damage the engine by
trying to run it without a prop. I suggest that you Google : " Bing 54
Carburator "
there is a wealth of setup and maintenance information on the net.

==================================================================================================================

Post by Aaron Jacobson
Hello everyone,
A friend of mine built an ultralight from scratch. He's never flown it
unfortunately due to an engine problem with his 447. When he starts
the engine (which presumably starts fine), the RPM's climb up until he
has to shut it off. It will not idle normally. He's been told that
there is an air leak (?) somewhere, but cannot seem to find the
problem. I believe this engine was brand new when he purchased it.
If you have any leads or advice, he would appreciate it very much.
Unfortunately I don't have anymore details than that as I'm just his
messenger and am not a mechanic of any sort.
Thanks in advance.