[NSRCA-discussion] YS discussion, add pushrod o-rings to your list of things to check

[Bill Glaze]

Excellent analysis, Bob.  It surely helps to understand the principles of 
the machinery.  I got caught in the 1.20 SC debacle; it got so that even the 
service people, ( Rick Matie and Richard Verano) couldn't make the thing run 
right.  With their co-operation, I cured the SC problem with a 1.40 FZ. 
Problem solved.
Bill Glaze
----- Original Message ----- 
From: "Bob Kane" <getterflash at yahoo.com>
To: <nsrca-discussion at lists.nsrca.org>
Sent: Thursday, August 13, 2009 4:09 PM
Subject: [NSRCA-discussion] YS discussion,add pushrod o-rings to your list 
of things to check


> One of the things that I found on my YS160DZ right after the NATS this 
> year was the o-rings that support/seal the fuel pump and exhaust pushrod 
> cover were worn and leaking.  This area is under supercharging pressure 
> (see last paragraph) and needs a good seal or a variety of issues can 
> arise.  In my case, there was an unusual amount of oil residue inside the 
> cowl and blowing back on the fusealge. The engine was also flat in the 
> midrange, but the idle and high-end were good.  Prior to the NATS I did a 
> partial rebuild and replaced the bearings, front seal, and piston ring 
> under the assumption the front seal was bad. The problem continued. It was 
> after the NATS that I discovered the worn o-rings. I replaced them and the 
> leaking stopped. The midrange issue was resolved also
>
> This past weekend another person's 170DZ started acting up.  There was 
> also evidence of an oily leak. He did not have replacement o-rings but 
> turned them around so the pump was sititng on a fresh surface.  This seems 
> to have cleared the leak and the engine ran good but other parts were 
> replaced so the source of the original problem may remain unknown.
>
> So, my recommendation is you replace the pushrod o-rings every season on 
> these engines. It is a quick job and you can do it without removing the 
> engine from the plane.  I never had this issue with the pre-DZ series of 
> engines, the added mass of the fuel pump causes them to wear out.
>
> Last paragraph:
>
> For those of you who study YS parts diagrams, you will notice the front 
> crank seal was introduced on the YS120SC.  It was on this engine that YS 
> drilled holes around the valve stem boss to utilize the area under the 
> valve cover as an air chamber and allow them to remove the bulky aluminum 
> box between the carb and head as on the "AC" series. This was a very 
> efficient way of storing the pressurized air without extra parts, but made 
> it necessary to seal every opening from the valve cover forward. So, the 
> pushrod covers, cam cover, and crankshaft all require good seals.
>
> Bob Kane
> getterflash at yahoo.com
>
>
>
>
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