another 'priceless' YS moment

[John Gausby]

Tom...I have to agree that the Yamada employees do get into a hurry during
assembly. I bought a 140FZ a few years ago that had ZERO valve clearance and
the brass regulator screw was about 1/8th of an inch above the housing. And
this engine was supposed to be ready to run?  No way!

I'm a true believer in disassembly and inspection before the first run. It's a
shame that a $700 engine is not assembled more carefully. 

Thanks for the warning....May not be a bad idea to foward your note to Dave
Shadel....although he doesn't make'em.....he just fixes'em......JG

On Fri, 13 Dec 2002 11:19:09 +1100 "Koenig, Tom" <Tom.Koenig at actewagl.com.au>
wrote:

> Hi all,
> 
> I just wanted to send out a 'heads up'  about
> my most recent DZ experience.
> 
> I'm not one to whinge too often, but my recent
> experience may just save
> someones model out there..or even themselves. I
> have been a most dedicated
> fan of the YS machinery fo many years, but even
> I am getting pushed to my
> limits.
> 
> I just fired up my brand spanker DZ 140. All
> went well, the usual little bit
> rich etc etc. After some gentle tweaking here
> and there I ran it up to full
> noise ( still rich and definitely not peaking
> out). All up, I ran it on the
> ground for a grand total of about  one and a
> half minutes. I then ran it up
> to full power once more just briefly, to check
> all was ok. As I throttled it
> back it went to about 1/3 noise when it
> promptly disassembled the mount and
> whole nose area of my plane. I quickly picked
> up the model and shoved it
> into the ground ( ala whipper snipper style) to
> stop the engine as it was
> about to explode. It was the meanest , fiercest
> detonation I have ever
> experienced. Infect it was the only detonation
> I have experienced since the
> dark ages of the OS 120SP!!! I thought this
> thing was going to take out
> everything and everyone in the surrounding
> area.
> 
> Now before you all jump to conclusions...I did
> everything right. After I had
> calmed down and was somewhat coherent
> again..(three days later!! ) I decided
> to check out the engine. This time it would not
> start but for a short burst
> and die out smoothly...just like a nice DZ is
> supposed to.
> 
> Anyway this story is long enough.....but
> ....the culprit was the diaphragm.
> I pulled this little sucker out and it was
> never fitted properly. You could
> actually see where the imprint had never made
> the seal around the housing
> edge/screw hole. The result was that as the
> diaphragm was doing its minutes
> worth of work, it pulled itself in from around
> the screw hole and the engine
> got the biggest gulp of air with the fuel and
> hence promptly blew the nose
> apart on my plane, spinner, prop etc. The
> diaphragm looked like it had 5000
> flights on it, it was completely butchered into
> position. 
> I think the assembly worker must have been in a
> hurry to get home that day
> to have his plate of Sushi.
> I have since checked out another brand new
> (never run DZ) and the diaphragm
> there too, was NOT fitted properly.
> 
> Guys...BE CAREFUL!!!!
> 
> In my opinion all Yamada needed to do was
> increase the 'land'area
> surrounding the pump diaphragm by about half a
> millimetre to ensure proper
> grip and no chance of a misalignment causing
> leakage.
> 
> I wonder wether this is the 'point of
> origin'for some of the more serious
> faults some engines develop?
> 
> I have since replaced this diaphragm myself (
> very, very carefully,being
> careful not to twist it as it goes into
> position) and sofar it appears to be
> running like a swiss watch........
> Then again...after replacing all the bits it
> destroyed, and repairing my now
> very average looking nose area of my plane...it
> might have been cheaper to
> just buy a Swiss watch!!
> I cant wait to see the bill from the therapist
> (which I now need due to all
> the snide comments from the OS two stroke
> brigade!!!) But seriously guys..it
> is an area of concern.
> 
> I apologise for giving the engine 'bad press'
> but it truly frightened me!.
> 
> Tom
> 

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