A puzzle for engine guru's

[J D 8]

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 8]

[MaL]

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 Miller]

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

[Ron Gray]

Slug, bug, fly or similar?

[john stones 1 - Moderator]

Alien lifeform present.

[Richard Wills 2]

blocked breather? case full of oil?

[David P Williams]

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

[Jon H]

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 Watkins]

Posted by Richard Wills 2 on 16/11/2017 13:30:55:

blocked breather? case full of oil?

Agree with Richards breather

Or

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

[Eddy Barker]

Choke closing.

[Flyer]

Had you connected the filler pipe to the carb John?

Soz, just seen Denis had suggested that

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

[Manish Chandrayan]

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 H]

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

[Engine Doctor]

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 6969]

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

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

Cheers

Chris

[J D 8]

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.

[bert baker]

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 Ovenden]

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

[Martin Harris - Moderator]

Slug of congealed oil partially blocking the exhaust outlet?

[Ron Gray]

Throttle servo connected to choke.

[PatMc]

Filler pipe not blocked so exhaust pressure to tank not effective.

[cymaz]

When you open the throttle the clevis pushes the choke shut?

[Mike Stevens]

Not an expert but as above ^^^^^^^

[stevejet66]

A meat fly wedged in the glow plug