YS FZ91 Problem

[Troy Newman]

If it has been back for service then the problem is inside the model.
Richard runs them all on a test stand before they leave his shop. He makes sure that they work and are all setup.....


SO .......next step....

Motor Mount loose?

Throttle servo bad? crappy throttle servos are a common occurrence. The thinking is well its the go handle....all it has to do is move the throttle works. Well many cheapy servo are not very good at holding position and enter the vibration that might be involved especially at idle....Well they will jump around.
I tend to use a very good servo on the throttle....

Idle just too low? should be 2000 or maybe 2100-2200...not 1600-1800
Fuel used? Many times the low nitro fuel like 10 or 15% will have inconsistent idle this is why you should use at least 20% Nitro

Tank problems or maybe a fuel filter that is leaking or partially clogged up....Under full power sometimes a clogged or restricted fuel filter will not show up as easily as its got such a high flow rate...at idle the flow rate is less and sometimes a partial clog in the filter...same thing for leaks.

Plug? OS #F or YS plug...and its in good shape? Maybe trade it out.

If all this doesn't help then try some leak free gaskets to stop any leaks if there are any...my guess is no because Richard would have replaced any gaskets.

Troy Newman
  ----- Original Message ----- 
  From: Bill Glaze 
  To: discussion at nsrca.org 
  Sent: Thursday, January 29, 2004 10:20 AM
  Subject: Re: YS FZ91 Problem


  He stated that it's been back to Richard already; they haven't fixed the problem.
  Have they run the engine on a test stand? Sometimes that can be very instructive.  I know that the engine works well on the ground, only problem being at idle for landing.  How does it take prolonged idle in the air if landing isn't intended?  Frequently, the longest period of time the engine is at idle, is in the landing setup and landing pattern.  What kind of RPM's is the engine set for at idle?

  Bill Glaze

  Troy Newman wrote:

If its a new motor send to YS Performance. Richard and crew will fix it up
right as rain....it will only cost you the $5 for shipping to him.

Especially if its a warranty thing.



TN
----- Original Message ----- 
From: "Ed White" <edvwhite at yahoo.com>
To: <discussion at nsrca.org>
Sent: Wednesday, January 28, 2004 10:11 PM
Subject: YS FZ91 Problem


  Folks,

We have a club member who is really interested in
pattern and bought a ARF pattern plane and put a YS
FZ91 in it to fly Sportsman and Intermediate.  The YS
has been a problem since he bought it.  It starts
easily and runs great on the ground, idles beautifully
before take-off, has good power in the air and flys
the intermediate sequence well.  Then he sets up for
landing and on the downwind or base leg the engine
quits.  I don't mean occasionally quits, I mean every
stinking time.

This is a very low time engine and the only time I've
seen it land under power was when the throttle linkage
slipped and he couldn't make it idle.  We've checked
for pressure leaks, run the same magnum fuel I use in
my FZ140, tried the idle leaner, tried the idle
richer.  He sent the engine back to YS who installed
an "updated" piston.  All to no avail.

I finally got him to give me the engine to tear down
and look at.  I haven't got very far into it, just
pulled the valve and airbox covers and diaphragm.  I
was sorta hoping to find an air leak but so far
nothing obvious.  Any thoughts/experience from the
community?

Thanks,

Ed

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