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A puzzle for engine guru's

Enya 90

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J D 816/11/2017 12:58:41
1119 forum posts
65 photos

A while ago I was pleased to purchase an Enya 90 advertised as little used for a very reasonable price.Upon arrival an inspection looking in through plug,inlet and exhaust holes showed it had hardly been used at all.

Engine was mounted in an old Freestyle Katana. The engine fired up straight away and ticked over just fine.I then ran it up for two mins,a slight adjustment on the main needel and all was well so a couple of days later off to the strip.

Having operated an Enya 90 in my DB Major Mannock for many years I was lookin forward to flying the Katana [ previously fitted with Irvine 60 ] with a bit more oomph available.

At the field all was as before so off we went. Penty of power but then after three min's it began to labour,thinking it may be over heating I reduced throttle some but shortly after it stopped and a deadstick landing was made.

Thinking it was just one of those things after waiting for other flyers to clear the strip we were off again for the same result. There was no sign of overheating but needle was opened a couple of clicks in case.

On the third attempt it kept going for just two min's and this time the dead stick landing was poorly judged resulting in the removal of the UC.

A few weeks later repairs were compleat and engine runs on the back yard resulted resulted in the same thing,good tickover,run up and down the rev's and hold full full power fine until the three minute mark when it would labour and stop.

All the usual suspects of fuel tank [ removed and replumed with new pipes and preassure checked ] Plug changed [ it was new and of the right type] The twin needle carb was removed and checked for leeks [ more than once,in fact every thing checked several times] Tappets were carefully checked but the result was the same,three minutes was as long as it would run for.

I have operated model [and other] engines for more than 50 years but this time I was stumped,so in the corner it went for a while.

Later I removed the engine from the model to do a compleat strip down but having done so I left it whole on the table while I was working.Several hours later I came back to find the problem had revealed its self.

As a bit of fun would you engine guru's like to hazzard a guess as to what the problem was? Ask any questions you like,but If no one gets it the answer will be shown tomorrow night.

Cheers John

J D 816/11/2017 12:59:17
1119 forum posts
65 photos


MaL16/11/2017 13:19:13
140 forum posts
13 photos

Did you leave the engine sitting upright on its bottom and notice upon returning that there was a leak from a hairline crack in the crankcase?

Peter Miller16/11/2017 13:21:50
9847 forum posts
1157 photos
10 articles

Matt, It doesn't matter if there is a crankcase leak on a four stroke. They have a breather pipa anyway.

Ron Gray16/11/2017 13:22:19
1407 forum posts
358 photos

Slug, bug, fly or similar?

john stones 116/11/2017 13:24:22
10345 forum posts
1475 photos

Alien lifeform present.

Richard Wills 216/11/2017 13:30:55
161 forum posts
7 photos

blocked breather? case full of oil?

David P Williams16/11/2017 13:52:01
817 forum posts
282 photos

Looking forward to the answer as I have identical symptoms with the Laser 150 in my Chipmunk.

Jon - Laser Engines16/11/2017 13:57:27
4570 forum posts
168 photos

Prop driver nipped up on the crankcase? that or the choke closed itself.

David, give me a call. Im sure we can sort it, but i have to confess, overheating is the most likely in the chippy unless its nicely baffled

Denis Watkins16/11/2017 14:32:45
3597 forum posts
166 photos
Posted by Richard Wills 2 on 16/11/2017 13:30:55:

blocked breather? case full of oil?

Agree with Richards breather


Fuel feed was not from the tank clunk exit, but from the breather or fill pipe.

Eddy Barker16/11/2017 14:53:56
44 forum posts
4 photos
Choke closing.
Flyer16/11/2017 14:54:39
509 forum posts
72 photos

Had you connected the filler pipe to the carb John?

Soz, just seen Denis had suggested that


Knew I should go leccy........

Manish Chandrayan16/11/2017 15:41:56
554 forum posts
65 photos

No engine guru I am, but a plugged breather is what I would bet my money on

Edited By Manish Chandrayan on 16/11/2017 15:43:02

Edited By Manish Chandrayan on 16/11/2017 15:43:24

Jon - Laser Engines16/11/2017 16:25:26
4570 forum posts
168 photos

if its a plugged crankcase breather you guys are suggesting that wont upset it. blocked tank breather would though

Engine Doctor16/11/2017 17:07:29
2205 forum posts
20 photos

Difficult to guess as many things can cause engines to go hard or labour before stopping. Were you using exhaust pressure To tank ? If not I would guess from your description a un-vented tank causing fuel starvation or congested crank case/blocked breather.


PS  Enya great  torquey engines and greatly under rated.

Edited By Engine Doctor on 16/11/2017 17:19:59

McG 696916/11/2017 17:47:42
2469 forum posts
976 photos

... maybe one of those "Drones fight back" thingies in your carb... ???

... OK then, grabbing my coat...



J D 816/11/2017 22:03:21
1119 forum posts
65 photos

Yes I was using tank preassure from the exhaust ED and pipes were connected the right way.Crankcase breather was not blocked but we are getting warm here

Nothing to do with bugs, slugs,flys,aliens or any other foreign items.sam_1369.jpg

bert baker16/11/2017 22:36:23
1285 forum posts
277 photos

I would sqwirt some air tool oil in crank breather and allow to drain

Possible bearings getting hot


Edited By bert baker on 16/11/2017 22:36:42

Edited By bert baker on 16/11/2017 22:37:09

David Ovenden16/11/2017 22:56:50
330 forum posts
17 photos

Pressure nipple on the muffler blocked or didn't have a hole drilled in it from new?

Martin Harris16/11/2017 22:58:47
8478 forum posts
212 photos

Slug of congealed oil partially blocking the exhaust outlet?

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