Old Enya 90

[J D 8]

When I was able to go flying last week [ bloomin weather ] I made a day of it mostly with my old Major Mannock. On the last flight of the day I noticed a reduction in power, engine sounded a bit odd but kept going. After engine had cooled I checked it over to find it seems like rear bearing is on the way out, some wobble when holding the prop, not much but a wobble.

  Took engine out today, boy some gunge down in the engine bay but structure still good after some 25years. I did epoxy the bay when I fixed up the old buss all that time ago.

 Went to undo prop nut and it just span but did not want to come off🧩,spun it some more pulling on the and prop and it came off.  The thread on the shaft has failed and not looking good in the Enya's odd prop bolt sleave thing. how this happened don't know but explains the lack of power as evidence of slippage on the prop and the prop washer.  Will investigate further to see if worth a fix.

Edited August 2, 2023 by J D 8
correction

[Engine Doctor]

The thread on the shaft doesnt look that good either. At the very least it needs a dye running up it to clean the thread.

[J D 8]

Hi ED,  A close look at the shaft threads show they have had it, all along the shiny section they have gone flat. Took the front housing off and there is no problem with crank shaft bearings, crank spins smooth with no slop done in the hand. It was just the slop at the prop and its driver that made me think bearing problem along with the fact there was just enough friction to keep the prop turning.

              However there is another issue, as you turn engine by hand there is every now and then a point where the engine sticks a tad [plug is out] timing housing bearing? Anyway not looking good for this unit.

[Jon H]

To check bearings properly you need to get the crank out and rotate it on your finger. I had an engine back here the other day that felt lovely and smooth when the crank was spun but removing the crank it revealed the rear bearing locked solid. It only felt smooth as the crank was rotating in the bearing. 

 

As for the crank, the threads do look pretty sad. The 90 used 5/16 threads didnt it? You might be able to get it turned down and use M7 threads on it. Bit of a strange size but i think saito use it. I dont know if the crank is hardened. I would assume not given the state of the threads. 

 

Do you have a closeup of the damage?

 

 

[Engine Doctor]

The tight spot is usually a bearing . I will pm you .

[J D 8]

  Stripped it down now and sadly other issues have been found.

  Had the bearings in hand Jon, all 4 good and run smooth. [ the extra 2 are for shaft to the cam gears for those who do not know Enya set up]

  As can be seen in pic teeth on the cam gear drive shaft are 3 broken 2  damaged on the section that drives the exhaust cam. 

Think this may have been due to a a bit of rust where its follower exits the housing to the pushrod making the follower action stiff, no other corrosion found.  How it was still running I don't know.   

It is an old unit that has been hauling my Major Mannock for 20 plus years and was used before I had it.      Will pm you ED.  John.

Edited August 3, 2023 by J D 8
correction

[Engine Doctor]

Hi I reckon that prop nut is the wrong thread judging by the way its damaged the crank thread ? Luckily those broken teeth on cam drive  didnt allow the cam to slip or busted valves would have done a lot more damage . PM just sent with pics.

[Paul De Tourtoulon]

My Enya .90 also has that type of prop nut.

[Jon H]

1 hour ago, Engine Doctor said:

Hi I reckon that prop nut is the wrong thread judging by the way its damaged the crank thread ? Luckily those broken teeth on cam drive  didnt allow the cam to slip or busted valves would have done a lot more damage . PM just sent with pics.

 

M8 forced onto 5/16? 

 

Shame about the pinion drive. Are the pieces floating around in the cam chest? It looks like a fairly historic injury to me. 

[RottenRow]

The Enya 90 - 4c has an M7 x 1.0mm crankshaft thread, see here…

 

http://sceptreflight.com/Model Engine Tests/Enya 90-4C (1).html

 

Someone with a lathe could take the diameter down to 6mm and then rethread it M6 x 1.0mm, same pitch so the die should follow the remains of the original thread, just cut a little deeper.
 

This might be irrelevant though, if the state of the rest of the engine doesn’t warrant it.

 

Brian.

[Jon H]

M7? my 120 4c was 5/16 i thought and they share a crank... Been a while since i ran it, just had it in my head it was 5/16. I know the 155 is M8x1 as i had to buy a special nut for it. I had to buy a special M7 nut for...something, saito 45 special maybe? cant remember. In any event, M7 is a strange size. 

[J D 8]

             It is the original prop nut that came with the engine over 20 years ago and Jon you are correct 90/120 share the same crank shaft. Have not checked what thread.

In close examination of the prop bolt what I thought was damage to the threads was just the remains of the crank thread that came with it when I undid the bolt, as I mentioned before when I turned the bolt to undo it it just spun, I had to pull on the prop for both to come away.

Bits,3 tooth bits were in the cam housing and the damage on the cam shaft gear is new. 

 Close look at the cam gears them selves shows no damage.

 On the day I was flying the Mannock had had four normal flights, on the fifth flight all I noticed was a bit of a lack of power at full throttle with a slower climb out and even after landing it was running ok. All rather strange, the engine and prop have been together many years though.    

                        John.

 

[Sheepish]

Don’t know if you’ve seen this on eBay?

 

Look like they have the other parts too but it is in Italy.
 

2E33 - ENYA 90-4C -- Distribution gear shaft - code 904C81

[J D 8]

   Thanks Sheepish, I had seen but along with needing a crankshaft, not wanting to spend that much on an old unit.

[Sheepish]

Hi John sometimes it’s just not worth the cost.

 

This company sometimes have rarer spares too if it’s worth the effort:

 

http://www.mecoa.com/

 

 

[Paul De Tourtoulon]

A shame, to me not worth the bother, there was an Enya .90 nib on leboncoin this morning at 150€ I did hesitate, but now it's gone.

[Manish Chandrayan]

21 hours ago, Jon - Laser Engines said:

M7? my 120 4c was 5/16 i thought and they share a crank... Been a while since i ran it, just had it in my head it was 5/16. I know the 155 is M8x1 as i had to buy a special nut for it. I had to buy a special M7 nut for...something, saito 45 special maybe? cant remember. In any event, M7 is a strange size. 

120 crank shaft is M7 and 120R M8

Since we are talking Enya engines on this thread, guess it's fine to ask for some advice regarding Enya parts. 

I need to replace some O rings on my 120R. Sizes I know are JIS P6 and P12. What material should I choose? Silicone/NBR/FKM? 

[Jon H]

We use NBR70 on lasers for pushrod tubes etc and viton for hot things like the exhaust 

[Manish Chandrayan]

5 hours ago, Jon - Laser Engines said:

We use NBR70 on lasers for pushrod tubes etc and viton for hot things like the exhaust 

Thanks Jon👍

[J D 8]

   With regard to how the crank shaft thread came away in the prop nut.

   Have had a similar issue with the blade retaining nut on my field topper [ grown up lawn mower] When undone the threads came away, the other way around this time with the nut threads remaining on the shaft.

Like the prop on the Enya the blade had been in place a long time [years] It seems that over time items screwed together can, due probably to vibration sort of weld themselves together and then break up when one undoes them.  Would be a straight forward fix except the nut is a left hand thread special I have to send for.

[J D 8]

 The old Enya 90 is up and running again,😁 starting and going well. A BIG thanks to Engine Doctor who was able to supply me a battered bottom end, but the internals were in good order.

[Paul De Tourtoulon]

Great engines, I have the .90 and 120.