REFLECTOR: Bad running Franklin

[Chuck Jensen]

Does kind of make you wonder how the Factory got a good 'test run' on it?  If they did the lashing trick just to make it run, it would seem they had to know there was a problem and they were more interested in pushing it out the door, then making sure it was right.

Chuck Jensen


-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
Behalf Of Scott Derrick
Sent: Monday, May 04, 2009 11:04 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Bad running Franklin


Thats amazing you figured that out!  WHo would have suspected a miss
marked crank or cam, from the factory no less!

Scott

Jerry Teitsma wrote:
> Several of you have helped me search for a solution difficulties in
> getting my Franklin engine running properly.  As a brief recap, I
> bought the PZL Franklin new about 5 years ago and flew it for about 26
> hours.  It never ran well which I attributed at least partially due to
> plug fouling.  The rings never seated properly.  I finally decided to
> re-sleeve the cylinders to get a softer grade of steel as liners.  I
> sent the cylinders to Davis Aviation for new sleeves. I fly out of an
> elevation of 8200 ft and it is difficult to get manifold pressure. 
>  
> After reassembly of the engine and re-installation, the engine ran
> worse than ever - back firing and popping and difficulty getting RPMs
> above 1500.  I checked everything - induction leaks, carburetor
> function, mags, wiring, plugs - you name it - nothing helped.  I tried
> to locate centerline intake valve angle but had difficulty locating
> these number.  Eventually, Phil Davis of Davis Aviation located these
> numbers and sent them to me. 
>  
> Saturday, mechanic John Welty and I used these numbers to check the
> center line angle for the intake valve on #1 cylinder and found the
> angle to be off 6 degrees.  Instead of 104 degrees, the angle was 98
> degrees.  So, the engine was pulled once again.  We took off the mags
> and accessories at the back of the engine and took off the rear
> cover.  Then, we pulled the starter ring, revealing the cam gear and
> crank gear. 
> When rotated, the mark on the crank gear meshed between the two marks
> on the cam gear (or the other way around) just like the book said it
> should but the center line angle was wrong.  We pulled the crank and
> cam gears and reset them so that the angle was correct.  We had to
> move the gear one tooth - about 6 degrees. 
>  
> After reassembly and reinstallation, we started the engine and it now
> appears to be running well.  I have not yet flown it but intend to do
> so this week.  It has been a frustrating - and expensive - several
> months trying to get this resolved. 
>  
> I'm not sure why this happened but have a guess.  It appears that the
> cam gear or crank gear was miss-marked.  When the engine was test run
> at the factory, it likely did not run at all well.  It appears that
> they opened the valve lash enough to run.  When we reset the valve
> lash to the proper amount, the engine would not run.  Now that the cam
> timing is correct, it runs with the proper valve lash.  Sounds
> incredible but I can't think of any thing else.
>  
> If anyone needs or wants a copy of the valve lift versus angle, please
> contact me and I will e-mail the table to you. Thanks to each of you
> for your suggestions and help.
>  
> Jerry Teitsma
> Granby CO
> 970-887-3910 (Phone/Fax)
> jerryteits at comcast.net <mailto:jerryteits at comcast.net>
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