<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman,new york,times,serif;font-size:12pt">You have seen some other answers, I forgot about the valve cover fix. It is easy and if it fixes your issue, great. The entire crankcase of the YS engine series is used for the supercharging process so a leak in any gasket can cause problems. Otherwise, a rebuild, including new bearings (at least the rear, both if you don't know the history of the engine), piston, ring, and gaskets.<br><br>Come to think of it, another seal that can can cause issues is the throttle barrel seal. If it is cut or torn you will have problems also. Be careful pulling the throttle barrel out, you can cut the seal on the machines edges.<br><div> </div>Bob Kane<br>getterflash@yahoo.com<div><br></div><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;"><br><div
style="font-family: times new roman,new york,times,serif; font-size: 12pt;"><font size="2" face="Tahoma"><hr size="1"><b><span style="font-weight: bold;">From:</span></b> Paul Horan <paul.horan@sbcglobal.net><br><b><span style="font-weight: bold;">To:</span></b> Bob Kane <getterflash@yahoo.com><br><b><span style="font-weight: bold;">Sent:</span></b> Monday, February 2, 2009 3:08:57 PM<br><b><span style="font-weight: bold;">Subject:</span></b> Re: [NSRCA-discussion] YS 140 FZ: loads up and dies 2500 - 4500 rpm<br></font><br>
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<div> I'm not sure of the time on the engine, it's used. But this only happens on the low end just above idle. Does that fit with piston rock ?</div>
<div>Paul<br><br>--- On <b>Mon, 2/2/09, Bob Kane <i><getterflash@yahoo.com></i></b> wrote:<br></div>
<blockquote style="border-left: 2px solid rgb(16, 16, 255); padding-left: 5px; margin-left: 5px;">From: Bob Kane <getterflash@yahoo.com><br>Subject: Re: [NSRCA-discussion] YS 140 FZ: loads up and dies 2500 - 4500 rpm<br>To: paul.horan@sbcglobal.net<br>Date: Monday, February 2, 2009, 1:56 PM<br><br>
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<div style="font-size: 12pt; font-family: times new roman,new york,times,serif;">How much time on the engine? Surging on these engines was a sign of piston rock, the fix was the DZ piston and a new ring (or drilling the gas holes from the top of the piston to the back of the ring groove). This was more of an issue on the L series, but your problem sounds the same form your description.<br>
<div> </div>Bob Kane<br>getterflash@yahoo.com
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<b><span style="font-weight: bold;">From:</span></b> Paul Horan <paul.horan@sbcglobal.net><br><b><span style="font-weight: bold;">To:</span></b> General pattern discussion <nsrca-discussion@lists.nsrca.org><br><b><span style="font-weight: bold;">Sent:</span></b> Monday, February 2, 2009 2:18:27 PM<br><b><span style="font-weight: bold;">Subject:</span></b> [NSRCA-discussion] YS 140 FZ: loads up and dies 2500 - 4500 rpm<br></font><br>
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<div> The problem is a YS 140 FZ that runs fine at idle and 40 to 100% throttle but loads up around 2500 - 4500 rpm. This is especially nasty since that is the rpm range for a smooth takeoff, once it goes to full throttle the engine does not develop full power (about 40% power) and dies. Plenty of smoke trail so it is not going lean. </div>
<div> Another symptom is on the ground running 2500 - 4500 rpm the rpm is not steady. </div>
<div>Help,</div>
<div>Paul</div>
<div>NSRCA 3606 </div></td></tr></tbody></table></div></div></div><br></div></blockquote></td></tr></tbody></table></div></div></div><br>
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