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Old Jul 15, 2014, 04:14 PM
Registered User
Auckland
Joined Mar 2010
283 Posts
supercollider -- you hit a home run with that comment about the engine sound doing rolls. This is what keeps me coming back for more. I was an electric man all the way until I could not stand listening to those lovely gas engines that kept flying and flying while I sat grounded charging bats for just another 6 minutes of flight!

Question for the long time IC engine flyers. I had to remove my muffler yesterday and was rather surprized to note a shallow scoring of the piston on the muffler side. I was always careful keeping the carb throat covered and the muffler side covered when installing to avoid foreign bodies getting in. Is this a common occurrence? I am new to these little ABC motors. It is only shallow and very narrow, but running a small screw driver across the line, the notching is clearly felt. Compression seems unchanged.
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Old Jul 15, 2014, 04:21 PM
EIEIEIO Classic is dway ta go!
flyinwalenda's Avatar
Northeast Pa. .Heyna or No?
Joined Aug 2009
1,870 Posts
The scoring could have been caused by a few things. As the piston was wearing in with the liner possibly a piece of raw casting near the exhaust opening was rubbing on the piston . I never opened up a new engine to see how well they are finished.
Or a piece of something was already inside the engine when it was started .
Or something was ingested at some point during running.
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Old Jul 15, 2014, 07:30 PM
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United States, MI, Waterford Charter Township
Joined Aug 2008
1,228 Posts
My guess is it ran lean or got hot for one reason or another. 2 stroke engines will very nearly always burn down on the exhaust side. Groove not good, but if it seems to run OK, I'd run it.
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Old Jul 16, 2014, 12:42 AM
Registered User
Auckland
Joined Mar 2010
283 Posts
Thanks for the replies -- both could be right. My concern is that it could be a small piece left from the manufacturing process as it lines up right on the edge of the cylinder lining cut out for the exhaust. Also when the fuel tank clunk clogged, I am pretty sure that the low fuel flow could have resulted in some overheating. It ran only a short while like this but I was surprized to see no exhaust oily residue at all during this time. I had no cowl on at the time so overheating still seems unlikely -- but it does not take much. If it does cause issues of course I can just get a new piston and liner -- some stores around $34.
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Old Jul 16, 2014, 03:10 PM
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Joined Jan 2012
7 Posts
Evolution 15 cc

I just purchased a Evolution 15cc gas engine from Horizon. From the very start it has been a very friendly engine, Easy to start, runs consistently and a little touchy on the needle valve. But they tell you that. When I first installed it in an airplane and ran it, I experienced RFI noise in the receiver (2,4 gig) at a certain rpm level. I called Horizon and they said they recommended a ferrite ring on each of the connections to the receiver as a filter, I am about to try this. It sounds to me that the ignition module is not very well shielded. I have never had to do this with a gas engine. Has anybody out there had this problem? By putting a ferrite ring on each of the servo leads to the receiver it seems they are admitting the problem.
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Old Jul 16, 2014, 04:32 PM
A geriatric flier
Watdazit's Avatar
Australia, NSW, Braidwood
Joined Nov 2008
790 Posts
Quote:
Originally Posted by Jerry Smith View Post
............... When I first installed it in an airplane and ran it, I experienced RFI noise in the receiver (2,4 gig) at a certain rpm level.................
How did you identify RFI noise? I would not blindly accept what Horizon techs will sometimes tell you.
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Old Jul 16, 2014, 04:48 PM
C.E.R.N. field tester
supercollider's Avatar
United States, NE
Joined Sep 2012
895 Posts
I would move things around before using any chokes. Get your ignition module up front, as far away from your rx as possible. Use a nylon clevis at the carb. Route the antenna wire toward the back of the fuse.
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Old Jul 16, 2014, 06:02 PM
A geriatric flier
Watdazit's Avatar
Australia, NSW, Braidwood
Joined Nov 2008
790 Posts
+1 and from what I understand RFI on 2.4 gig would require a noise generator something the size of a small car.
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Old Jul 17, 2014, 02:29 AM
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United Kingdom, England, Shrewsbury
Joined Oct 2012
61 Posts
Quote:
Originally Posted by Jerry Smith View Post
When I first installed it in an airplane and ran it, I experienced RFI noise in the receiver (2,4 gig) at a certain rpm level.
The one-and-only time I've had RFI problems was when the spark plug cap was loose. I take it you've double-checked the cap? They're incredibly tight to lock on when new (including the all-important 1/8th clockwise).
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Old Jul 17, 2014, 07:09 AM
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United States, TX, Leander
Joined Sep 2003
2,447 Posts
We worked on a new CDI zenoah 26 last weekend that had the wire braid separated from the metal boot. That was causing range check problems on a guys 72mhz. The boot was so loose it pulled off with little effort when we were working on it. Reattaching the boot and braid was an easy field fix.

This engine was bought used because the previous owner couldn't make it run right with 2.4.

We we amazed it even ran. The carbon thread inside the wire was a really loose connection on the boot plug connector.
Edwin
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