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Author Topic: ST 60 question  (Read 1090 times)

ChrisSarnowski

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ST 60 question
« on: July 10, 2011, 07:22:15 PM »
Hi Guys,

I have an ST 60 set up with a true venturi. It came to me pretty gunked up so I crock potted it (after removing NVA, venturi, backplate, glow plug).

Reassembled engine after cleaning and did what I thought was a decent job of aligning spraybar hole with the single hole in the venturi.

At the field today engine was hard starting then once started was rather unresponsive to the needle valve. So no flying with the 60 ship.

Could this be a result of spray bar hole mis-aligned with venturi hole? What size should the hole in the venturi be relative to the spray bar hole?

Should I be looking elsewhere for the problem (backplate seal, etc.)?

Thanks
Chris
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Offline Steve Helmick

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Re: ST 60 question
« Reply #1 on: July 10, 2011, 08:30:26 PM »
Might be just stuff in the spraybar or even a loose glowplug. Check all the screws for tight, too. Them's my ideas.
 H^^ Steve

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Online Bill Hummel

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Re: ST 60 question
« Reply #2 on: July 11, 2011, 06:00:39 AM »
Chris, you have at least three great ST 60 resources in your neighborhood: Dick Carville, Dave Cook and Len Harding.  Show them your set-up, and any one of them will solve it for you. The ST 60 is a friendly engine, an unresponsive NV is often dirty inside, or damaged, or even the wrong needle in the assembly!  Steve makes a good point with possible air leaks, too.  Hard starting:  is the ring free in the cylinder?  Good head seal?
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ChrisSarnowski

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Re: ST 60 question
« Reply #3 on: July 11, 2011, 08:26:35 PM »
Hey Bill,

Thanks for reminding me. I'll bring the engine to the field again this week and talk it over with the guys.

Compression is very good on the engine - turns over with a nice pop. Seems like a fuel system issue.

There was some discussion on the venturi hole size vs. the hole in the spray bar, as if something other than the needle was limiting the fuel flow.

How do you know (or can you know) if your ring is stuck or not without removing piston/liner?

Thanks,
Chris
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Offline Steve Helmick

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Re: ST 60 question
« Reply #4 on: July 11, 2011, 09:01:19 PM »
My most recent (Memorial Day weekend)  problem of that sort was junk in the spraybar. While pinching the muffler pressure line would make the engine rev up to normal, turning the NV in would make the rpm increase, decrease, increase again, and then decrease, but never come up to the right launch rpm. After a bad flight, I got it off the lines and did a ground run out of the pits. Got it running, opened the NV up until it would barely run, and cleared the stuff out of the spraybar. Danny Dirt wrote a post about doing the exact same thing with his .25FP in early June.

Another common cause of foolishness like that is using a small filter that clogs much too quickly...especially on a new plane/tank. Not much anything better than a CrapTrap, even if you have to leave the cowl off for a few flights. Huge capacity for accumulated chit. Once stuff quits showing up in the CrapTrap, put in the tiny filter if you must.  Don't forget which end goes toward the NV...Randy Powell had that issue recently.

Pete Peterson and I were starting his .25FP powered Bobby Hunt "Hole Shot" (I always call it the Hot Shot for some reason). Pete was twiddling the NV and it wasn't running well. I went to remove the twist-lock battery clip, and easily unscrewed the glowplug. I screwed it back in. The engine stayed running. Pete tightened the plug with the engine running (real bad idea, I think), and flew it. The engine ran lots better with the plug tight!  H^^ Steve 
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"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

ChrisSarnowski

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Re: ST 60 question
« Reply #5 on: July 14, 2011, 09:36:25 PM »
Hi Guys,

So I had some better luck with the Tigre 60 today at the field. I did check a bunch of things before today's flying session:

-Cleaned out spray bar and checked that needle could close off flow.
-Opened up the 'dripper' hole in the venturi a little bit.
-Checked head seal and screw tightness
-Replaced fuel filter
-Checked that Fuel tank was air tight.

The engine starts and needled better, and runs well in flight. Dick Carville and Len Harding were present 'just in case'  :) :)

Tank needs a little shimming to get even upright/inverting RPMs but it looks much better now.

Thanks,
Chris

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Offline Bootlegger

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Re: ST 60 question
« Reply #6 on: July 22, 2011, 03:24:55 PM »
  I am looking for the bore of the Tiger 60 so that I can search for head shims that will inner change with it.
 Any suggestions?
  Thanks a lot, Gil       <=
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Offline Larry Fruits

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Re: ST 60 question
« Reply #7 on: July 23, 2011, 06:46:28 AM »
Gil,
 You might give Frank Bowman a shout. He made some head gaskets for me a while back. He is listed on the forum.

 Larry
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