91FZ about to be melted down and recyled
07-07-2003 | 08:45 AM
#1
Thread Starter
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91FZ about to be melted down and recyled
Dave,
HELP!
Can you prevent me from throwing my YS into the recycle bin and buying an OS instead? I am so frustrated with it I could give it away for free just to see the back of it.
On Saturday I tried to use my YS 91FZ that has not been used for a while. It was up to its old trick, seems fine on the ground but 4 minutes into the flight, all done around half power, the throttle stops working, the engine starts surging and finally quits.
Back home I pumped up the entire fuel system – lines, tank and everything, to 12 psi and left it for a while. It held the pressure so there is no leak in the system. Checked valve gaps were 3 thou.
On Sunday I turned the regulator in just over a turn since it was quite a bit proud of the casing. I spent a long time following the instructions about setting the idle. At a fast idle around 3500, the engine would suddenly stop with no warning after about 20 seconds. I have no idea what this indicated since it did not speed up or slow down or run rough before suddenly stopping. At idle 2.5k it would speed up a bit. This indicated lean so I richened it by turning the idle needle clockwise. It will hold the idle but it is not smooth, revs jump 2.3k, 2.5k, 2.4k. 2.2k. 2.5k and so on. Then transition to full power was good with no hesitation after 30 seconds of idle. Cycled the engine up and down many times to prove it worked well every time after 30 seconds at idle. Released model for take off, opened the throttle and it paused for 2 seconds before spluttering up to full power! Can’t believe it. This indicates rich at idle? I leaned it off a little at a time by turning idle needle anti-clockwise but it just gets back to the state of speeding up and dying at idle so I made it richer, again get perfect response in the pits and as soon as on the runway it behaves rich again. In sheer frustration I left it like that, did not touch the needles or regulator again and had about 7 flights just accepting the delayed response. Engine would work until near the end (around 7 minutes into flight) when faint signs of mid-range surging start to appear, if I notice in time I can get it up to full throttle and clear it, if I notice late then throttle stops working and it surges until it quits. Top power fluctuated every flight, one flight it had the surplus of power to pull out of a hover, next flight had not enough power to hover. The idle is carefully set for 2500rpm and the engine will idle happily down to 2100, gets a bit rough below that. Yet every time I come back to idle to land, the engine quits on finals, if it has not already quit due to mid range surging.
Then when started for the eighth flight the engine went mad at mid range immediately, surging markedly until it stopped. It would not start again. Left it to cool down and eventually it started again but was really reluctant to, full power was ok but mid range was surging until the engine stopped. I had not changed anything! Fuel system appeared to have normal pressure when fuel dot removed. Packed up and went home, YS now has an appointment with the bin.
I use an APC14x8, 20/20 fuel, new OSF plug. Top revs 8.8-9k.
What was I doing wrong that I could not get the transition to work properly? Why does the top end power change so much each flight? Why does the idle work perfectly on the ground but quit at idle at the end of the flight? What are the likely causes of the engine’s midrange suddenly going berserk when nothing had been altered. I am sick of the problems with this engine, this is its last chance! HELP!
Harry
HELP!
Can you prevent me from throwing my YS into the recycle bin and buying an OS instead? I am so frustrated with it I could give it away for free just to see the back of it.
On Saturday I tried to use my YS 91FZ that has not been used for a while. It was up to its old trick, seems fine on the ground but 4 minutes into the flight, all done around half power, the throttle stops working, the engine starts surging and finally quits.
Back home I pumped up the entire fuel system – lines, tank and everything, to 12 psi and left it for a while. It held the pressure so there is no leak in the system. Checked valve gaps were 3 thou.
On Sunday I turned the regulator in just over a turn since it was quite a bit proud of the casing. I spent a long time following the instructions about setting the idle. At a fast idle around 3500, the engine would suddenly stop with no warning after about 20 seconds. I have no idea what this indicated since it did not speed up or slow down or run rough before suddenly stopping. At idle 2.5k it would speed up a bit. This indicated lean so I richened it by turning the idle needle clockwise. It will hold the idle but it is not smooth, revs jump 2.3k, 2.5k, 2.4k. 2.2k. 2.5k and so on. Then transition to full power was good with no hesitation after 30 seconds of idle. Cycled the engine up and down many times to prove it worked well every time after 30 seconds at idle. Released model for take off, opened the throttle and it paused for 2 seconds before spluttering up to full power! Can’t believe it. This indicates rich at idle? I leaned it off a little at a time by turning idle needle anti-clockwise but it just gets back to the state of speeding up and dying at idle so I made it richer, again get perfect response in the pits and as soon as on the runway it behaves rich again. In sheer frustration I left it like that, did not touch the needles or regulator again and had about 7 flights just accepting the delayed response. Engine would work until near the end (around 7 minutes into flight) when faint signs of mid-range surging start to appear, if I notice in time I can get it up to full throttle and clear it, if I notice late then throttle stops working and it surges until it quits. Top power fluctuated every flight, one flight it had the surplus of power to pull out of a hover, next flight had not enough power to hover. The idle is carefully set for 2500rpm and the engine will idle happily down to 2100, gets a bit rough below that. Yet every time I come back to idle to land, the engine quits on finals, if it has not already quit due to mid range surging.
Then when started for the eighth flight the engine went mad at mid range immediately, surging markedly until it stopped. It would not start again. Left it to cool down and eventually it started again but was really reluctant to, full power was ok but mid range was surging until the engine stopped. I had not changed anything! Fuel system appeared to have normal pressure when fuel dot removed. Packed up and went home, YS now has an appointment with the bin.
I use an APC14x8, 20/20 fuel, new OSF plug. Top revs 8.8-9k.
What was I doing wrong that I could not get the transition to work properly? Why does the top end power change so much each flight? Why does the idle work perfectly on the ground but quit at idle at the end of the flight? What are the likely causes of the engine’s midrange suddenly going berserk when nothing had been altered. I am sick of the problems with this engine, this is its last chance! HELP!
Harry
07-07-2003 | 01:39 PM
#2
Senior Member
91FZ about to be melted down and recyled
Has this thing ever been in here?
If it hasn't, you need to get it in asap. It sounds like it has a bad piston, although we can't be sure until we see it.
YS Service
1295 Industrial Court
Gardnerville, NV 89410
If it hasn't, you need to get it in asap. It sounds like it has a bad piston, although we can't be sure until we see it.
YS Service
1295 Industrial Court
Gardnerville, NV 89410
07-07-2003 | 02:06 PM
#4
91FZ about to be melted down and recyled
I live in the UK. What is a "bad " piston Dave?
---------------------------------------------------------
Means it's shagged
I had a 140 do the same thing. Replaced piston and ring - runs like new
Peter
---------------------------------------------------------
Means it's shagged
I had a 140 do the same thing. Replaced piston and ring - runs like new
Peter
07-07-2003 | 02:12 PM
#5
Senior Member
91FZ about to be melted down and recyled
So what if you live in the UK? We work on engines from all over the world.
Bad piston might be leaking on the upstroke enough so that it effect the operation of the regulator. Hard to say exactly without seeing it.
Bad piston might be leaking on the upstroke enough so that it effect the operation of the regulator. Hard to say exactly without seeing it.
07-07-2003 | 03:23 PM
#6
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From: London, UNITED KINGDOM
91FZ about to be melted down and recyled
If you don't want the expense of sending it to the states, try sending it to Phil Williams of Probuild. He usually has a quick turn around and does a good job. Have a look at his website for contact details www.probuild-uk.co.uk
James
James
