<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;"><DIV>Mike,</DIV>
<DIV> Be careful with the valve lash adjustments. I believe they should be done "cold" on a YS. Don't set them when the engine is cold, then run the engine, then re-adjust. It's normal for the lash to change as the engine warms up. That's why we have hydraulic lifters in automotive engines. I know model engines are different but the physics are the same. :) If the instructions tell you to set the valve lash when the engine is cold then that's really the only time you should do it.</DIV>
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<DIV>John Pavlick<BR><BR>--- On <B>Fri, 8/21/09, Michael Cohen <I><precisionaero@hotmail.com></I></B> wrote:<BR></DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: rgb(16,16,255) 2px solid"><BR>From: Michael Cohen <precisionaero@hotmail.com><BR>Subject: [NSRCA-discussion] YS engine follow up<BR>To: nsrca-discussion@lists.nsrca.org<BR>Date: Friday, August 21, 2009, 2:51 PM<BR><BR>
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Well, I ran the YS engine I had trouble with the other day and am reporting back with my findings. First, the inspection and changes. I looked for cracks or splits in the o-rings and saw none. I went back to flush on the pump (it was about 3/4 of a turn out). After starting the engine and running on a high mid throttle and back down to idle, I tweaked the pump slightly to keep a good 2000 to 2200 idle. I left the high speed set where it was, but after running at full power, I went to get the tach and the engine would die abruptly. I decided to check the valve clearance and reset it to .0015 to .0020 inches. Since the valve cover was off, I did a quick wet sand on the valve cover. Since I was out 2.25 turn on the main needle (much further than any other DZ I have), I decided to simply turn it in to 1.75 turns and see what would happen. I know for a
good controlled experiment, one should not alter more than one thing at a time, but the engine seemed to work just fine now. High end power was up to 7400 to 7500 RPM on an 18.1 X 10 prop from the 7200 (but rapidly sagging) setting before. Richening the high setting slightly cause a slight drop in RPM, so I left it at 1.75 out and double checked the idle and the transition from idle to full power. Everything seems to work great, but I will try it in the air on Sunday before feeling more comfortable.<BR> <BR>In summary, from the previous, issue free running of this engine in a Brio, I made the following changes:<BR> <BR>1) Had a mid air and buried the engine nicely in a plowed field.<BR>2) Disassembled, inspected, cleaned, and reassembled the engine (using klotz synthetic oil as a lube) and installed it into an Eclipse<BR>3) Used a 18.1 X 10 2 blade in place of the 15.5 X 12 4
blade<BR>4) Ran the engine on the ground to check its operation, all seemed normal<BR>5) Had one flight on the engine last weekend and on the second flight, the dying at full power issue popped up. Admittedly, it was a very humid day last weekend.<BR>6) Reset the pump to flush and checked the idle for a nice 2000-2200 run. The high power setting issue was still present.<BR>7) Reset valve clearance, sanded the valve cover, and reset the high speed needle to 1.75 turns out. Problem solved!<BR> <BR>So, now for the educational questions:<BR> <BR>Could the high speed needle being so far out have cause the abrupt high speed "flame out"?<BR> <BR>Does switching from a 2 blade from a 4 blade make a difference and why?<BR> <BR>Does the valve clearance being in the .003 range instead of the .000 to .002 (as recommended) make that much of a difference?<BR> <BR>Could an air leak
cause this high speed flame out problem?<BR> <BR>I am interested to know so I can someday become the Troy Newman of the East (maybe) for YS engines. I don't get a heck of a lot of flights per year, so my statistical database is lacking. But that said, I did help two people with their YS engine troubles at the Weak Signals contest so I must be learning something! Thanks all for the help.<BR><BR>
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