YS FZ91 Problem

[Anthony Abdullah]

The first time I ever flew from pavement was at the Com Air contest. I was flying sportsman with my ultra reliable YS61 AR. First flight, take off, trim pass, not so much as a burp. Pull up for stall turn, rudder over, downline. I pull out, advance the throttle, nothing, land dead stick. I checked all the usual suspects, pressure good, check valve good, install new Enya #4 plug and crank her up. Idles fine, transitions great, time to try again. Second round, exactly the same problem. Getting frustrated, more thourough check between rounds, all plumbing changed, restarted the engine. Idles nose up, nose down, sideways, inverted (which is now upright). Will idle forever and snap transition. Round three very optomistic. Take off alls well, stall turn and hold a little power just to be sure, comes back to life with no problems. Feeling good, next down line back off the throttle, pull out, nothing. After a full wasted day of flying and trying everything I could think of, Margretta said,
 it sounds like you are cutting it off at the bottom. Light comes on, I had the stinking idle set very low to keep it from rolling away on the pavement before take off. It would idle forever on the ground, but when it unloaded in the air it was too low. It could've even been a combination of too soft a motor mount with no nose ring, low idle and a crappy throttle servo. 
 
Moral of the story:
Check the simple stuff first, perhaps your trim is just too low. If that is the case, it will always run great on the bench. Please let us know what the problem was when you get it worked out.    

Bill Glaze <billglaze at triad.rr.com> wrote:
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 upright 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 PMSubject: YS FZ91 Problem  

Folks,We have a club member who is really interested inpattern and bought a ARF pattern plane and put a YSFZ91 in it to fly Sportsman and Intermediate.  The YShas been a problem since he bought it.  It startseasily and runs great on the ground, idles beautifullybefore take-off, has good power in the air and flysthe intermediate sequence well.  Then he sets up forlanding and on the downwind or base leg the enginequits.  I don't mean occasionally quits, I mean everystinking time.This is a very low time engine and the only time I'veseen it land under power was when the throttle linkageslipped and he couldn't make it idle.  We've checkedfor pressure leaks, run the same magnum fuel I use inmy FZ140, tried the idle leaner, tried the idlericher.  He sent the engine back to YS who installedan "updated" piston.  All to no avail.I finally got him to give me the engine to tear downand look at.  I haven't got very far into it, justpulled the valve and airbox covers and diaphragm.  Iwas sorta
 hoping to find an air leak but so farnothing obvious.  Any thoughts/experience from thecommunity?Thanks,Ed__________________________________Do you Yahoo!?Yahoo! SiteBuilder - Free web site building tool. Try it!http://webhosting.yahoo.com/ps/sb/=====================================# To be removed from this list, send a message to# discussion-request at nsrca.org# and put leave discussion on the first line of the body.#    

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