J'EN 57 Engine

[Peter Roberts]

Have just bought a J'EN .57 from Just Engines to replace my OS 46AX in a Flair Kite which I think underpowered on the 46.
I intend to fit a Genesis pipe to it.

What has anyone else's experience been. I also had a recommendatuion from JE to use min 2% castor fuel with it. I usually use ProSynth which they don't seem to like -has anyone any experience on this engine please?

[Danny Fenton]

I have recently bought a Jen 57, am running it on Model technics GX-5, 20% castor. starts a dream (by hand) and seems to have a shed load of power even though not yet run in. Was warned that the trhottle response was either all or nothing, ie peaky, however mine throttles progressively. Its not got the build quality of an OS but its not the same price! I have heard several in my club berate the engine for having a soft conrod, when I mentioned perhaps thats why Just Engines demand a min of 18% oil, 2% castor! I was told that was rubbish. just Engines would not add notes in the packaging about warranty being invalid if the oil content is ignored for no reason, surely?

[Peter Roberts]

That's what I wondered too about the castor content. I'm interested to hear of your experiences running it and more importantly the asy start. How difficult is the run in procedure? I've previously bought OS and one Irvine and they ran beautifully out of the box. Some of the older guys at the club believe you can run them in in flight!

[Danny Fenton]

I guess it depends on the model, and your feel as to its reliabilty. I have put mine in a Wot 4 and to be honest I am sure the Jen would pull it around all day on a third throttle. So leaving it rich while running in could be done. I am not happy until it will sit at idle for a minute and pick up instantly when you open The throttle, this one isn't quite there yet. I need to trust an engine before I will fly with it, I will probably run a couple more tankfuls through. There is a noticeable vibration at certain rpms, which I am assuming is due to the prop I will have to re-check the balance. As I said I haven't had mine long, can I suggest we compare notes along the way??
As for starting, Two choked rotations and 5 flicks had it running, subsequent starts were first or second flicks.

[Peter Roberts]

I'll happily compare notes as we go along. I'll post once I've received it and got it running. I had a Genesis pipe on my previous 46AX and JE think it should fit onto the J'EN .57 OK - should be interesting. What sizes of prop and model are you using it with?

[Danny Fenton]

Hi Peter, I am using mine in a Chris Foss design Wot4 it has wingspan of 56" and an all up weight of about 4 and a half pounds. Running in is supposed to be done on an 11 x 6, which is what I have used (master Airscrew in my case) but I think I will try a 12 x 6 or 13 x 4 as I don't want to tear through the sky LOL. Holding the model vertically at two thirds throttle it just wants to go up!
The Jen is pretty highly tuned and the power comes in with a wallop, I hope you still have a controllable throttle with that pipe???? I got the JEN Super Quiet pipe as the club I fly with have strict noise levels. Should be interesting :)

[John MacDonald]

I trust that you will run the engine in on a standard muffler before running on a pipe?

[Slopetrashuk]

It is actually more beneficial to run a motor in on a tuned pipe as the scavaging of the exhaust port as the pressure wave travels the front cone of the pipe removes the debris associated with combustion.

[Peter Roberts]

Thanks for the suggestions. I have to admit that I'm asking them to run it in for me as they offer the service. Maybe lazy but for £15 and the time it saves me I hope it'll be worthwhile.

[Peter Roberts]

Received the engine this afternoon. Thanks Jenny and Just Engines - it arrived and seems nicely run in. Had it on the Flair Kite in place of my 46 AX in no time flat. My friend Jerry made me (notice the reluctance) get it out of the workshop and test run it - ran sweet as a bird although the servo needs adjusting for max min throws. Sounds good. Maybe the bottom end will need some adjustment as from slow it hesitates before picking up. Now all I need is a couple of hours to get it set up and balance ready for the field. Then a bit of dry weather!! Hmmm. We're in Sussex and, like lots of the North, are flooded in the fields. Even the planes need wellies to get on the strip!

[John MacDonald]

With respect to Andy,scavenging is no help to piston, conrod and bearings at the higher r.p.m. and / or increased stresses resulting from the pipe operation.Running in under "milder" conditions should surely be kinder to the engine and be beneficial in the long run. Of course, life in the fast lane usually doesn't result in an old age pension!

[Slopetrashuk]

John, you're assuming that a tuned pipe means higher rpm which is not always the case. True higher rpm is often a product of the increased power resultant from the extra fuel charge ignited but it need not be.
Additionally most manufacturers quote BHP figures at around 17,000rpm for an average two stroke which is far below that which most will see in our applications. Many companies now also forgo the running in process as modern materials, fits and finishes simply do not require it like the older ringed motors used to. Things have moved on.

[Peter Roberts]

When I ran it for the first (and so far only) time it had the pipe fitted. Sounded sweet as a nut and suprisingly quiet. I had forgotton how quiet the pipe makes it at low and medium revs especially.

I was short of time so hope to get further this weekend. As I was running it I noticed fuel leakage in the tank bay - later established to be a split in the tank to engine feed pipe. Have to find out why. Does anyone use the clamp wires for fuel tubes fastening onto the tank tubes? I'm wondering if that is what has caused it?

[Danny Fenton]

I had a Sullivan tank recently, and it had some thin wire included that you were supposed to lock the silicon tubing to the brass. We never did this years ago and I never had any problems. I am not saying it isn't a good idea as we have all had a clunk fall off into the bottom of a sealed fuel tank at some time I guess. But if you twist that locking wire a fraction too much it is bound to nick the tubing.
I am not sure I would lock the lines outside of the tank, just the clunk.

[Peter Roberts]

Thanks Danny, I'll be interested to see what anyone else thinks but am tempted to try your suggestion.

I used to have one of the Dubro? one way fuel valves which was great and meant you only needed two outlets to the fuel tank but found that the pressure of the fuel entering the tank through the clunk blew the it off the pipe.

I've tended to put wires on all my pipes because I worried about tank pressure blowing them off in flight and losing the engine.

[Danny Fenton]

I usually fit one feed for the clunk and two feeds bent towards the top of the tank, one is fed by exhaust pressure the other I bring out on a short length of tubing, (just hangs outside of the cowling) I push an allen bolt into this to seal it under normal circumstances. So to fill the tank remove the blocking screw from tube and connect pump, fill until fuel seen in pressure feed to pipe (remove if you dont want an exhaust full of raw fuel) Draining is not quite so easy as you have to flip the model over and reverse the pump. Remember to replace the blocking screw before flight. The pressure in the fuel tank is very low.
I fit a fuel filter to my filling system, not the model. Less to fall apart/come apart in flight, though you must ensure your system is clean in the first instance.

[Danny Fenton]

PS like the Avatar Peter, are we all copying Steve LOL
Are any of us actually flying or just staring skywards for the camera.....

[Peter Roberts]

Its the only picture I've got of flying in portrait style. I think however that if you look closely you can see I'm catching flies!

[Danny Fenton]

LOLOL.... me too

[John MacDonald]

Regarding "Pipe running in", yes, the extra power may be utilised by running a larger prop, or steeper pitch prop,since power=torque; rather than "same prop, more RPM", either way this being more stress on con-rod and piston as I stated in my original post.
Fuel tube and brass pipes; my practise, round brass tube ends, rough up slightly where fuel tube goes,two or three turns of plastic tape, and wire over that, the plastic tape lessening the chance of the wire cutting into the fuel tube.
Filter between tank and carb, as well as on exit from fuel container.

[Peter Roberts]

Thanks John,
I like the idea of tape to re enforce the tubes and will try what you suggest on the tubes. I use a sinter clunk in all my tanks for filtration because I normally use 3 pipe system so it is effectively between tank and carb.

Re pipe utilisation I rarely run my engines "at full bore" except when doing certain aerobatics. My previous 46AX didn't have a particular running in period and behaved well but hadn't quite enough grunt even with the pipe for the application of running the Kite (heavy plane) I intend, therefore, to use the pipe on the J'EN to add grunt on those few occasions when I really need it and at others make the engine more efficient and therefore quieter. I'm therefore relying on the inherent power of the Engine itself to provide the grunt for the Kite rather than the pipe. Does that work?

[Danny Fenton]

Hi John, I assume you are suggesting the tape is used on the pipework external to the tank not for the clunk feed inside the tank?

[Mike Bell]

I don't have any experience of the 57 but I presume it shares most of the same bits as the 56 which my son has been using for the last couple of years. If so our experience may be of interest. This engine proved to be easy starting with good throttling (which was pretty importand as it was being used for 3D in the Stiletto featured in RCM&E a couple of years ago).
The experience wasn't all problem free though. The first enging developed a knock during running in which turned out to be a worn big end. Just Engines repaired it promptly with the comment about using castor in the fuel, which we were anyway.
The repaired engine performed well until a few months later the piston split around the gudgeon pin hole and exited through the crank case. JE replaced the engine free of charge but again blamed under oiling. In JE's defence I have to say that we were trying to squeeze every ounce of power out of it for the 3D stuff, but this didn't mean outrageous revs or super lean running so the explosive demise was still a bit of a surprise. Anyway, this replacement engine continued to perform well until a familiar knocking noise indicated another worn big end. On this occasion I simply ordered a spare from JE and fitted it myself. The phosphor bronze bush on the original had worn egg shaped.
In summary I would say that the 56 was a good performer albeit a little fragile in the con rod area. So long as you are using a good fuel, don't run it lean and don't try to wring it's neck you shouldn't have too many problems and even if the con rod does wear the replacements are cheap. If JE have uprated the con rod for the 57 I would expect it to be an engine well worth having

[Danny Fenton]

Thanks Mike that is very interesting, I gave mine a bit more running today, JE suggest the needle should be around 2 - 2.5 turns. I am at 1.5 turns what sort of setting are you using?
I had some vibration which ahs been cured by a more carefully balanced prop. I will have to listen out for the big end. I am using 20% castor in mine, just in case.

[John MacDonald]

Tape on the clunk end as well as exterior to tank.I use strips of thin Mylar draughting paper,has a frosted surface so pencil/ink sticks.Seems inert to fuel etc;can only be stuck well with contact adhesive.
Mike, your comments bear out what I said about big ends and pistons!
Could be the 57 needs more developement in the con-rod/bearing area to handle max power and last.Titanium sleeve perhaps?
As for the piston; different material, or thicker walls? Or just don't ask so much of it!