Engine run-in questions from a noob

I took a break from hacking the T180 to bits, and decided to try firing up the SC 46 engine I got last week. It was sold as used on fleabay, but didn't seem like it had been run much.

Over the last week, I stripped and cleaned it out. It was already pretty clean inside, with very little signs of running. No soot on the exhaust ports, and the piston and liner were very clean.

The only issue was that it looks like it had been stored without after run oil, so there was some very lightly rusty residue in places. I ordered a new internal bearing a replaced it, and lightly rubbed off the rusty residue from the crank shaft.

So, onto starting it. I had it mounted on the test stand I'd build last week. I put in some 3-in-1 oil after rebuilding the engine, so that needed burning off first.

It was a bit rough to get going, and didn't pick up revs very well. At the low end, it always died. So I adjusted the low needle to lean it out, and it then ran very nicely at low revs, without cutting out at closed throttle.

I then leaned out the high end until it was just hitting that sweet exhaust note. I ran a tank through at mid to low revs, and an occasional run at full throttle.

The issues I found were that the transition from low to high wasn't very smooth, with some stuttering - what would be the cause of that?

The other thing I noticed, is that there was fuel dripping from below the prop, so I think the front bearing is leaking - I've just ordered a new one. I suppose in hindsight I should have just replaced both at the same time. What issues would a leaky bearing cause in the engine running?

And lastly, if the engine runs at minimum throttle without cutting out, how do you kill the engine when it's on the plane? :lol:

I'll wait till I've replaced the bearing before running it again, and it'll also give me a chance to inspect it after it's first run.

The stuttering sounds like it's to rich at idle, when you say it won't cut out is the the throttle body fully closed? there's normally a stop screw you can adjust.
If it is fully closed then it has a air leak, probably from the nva.
The leak from the front I wouldn't personally worry about to much, at least you know the front bearing getting lubricated!
As for running in I would give it a couple of tankfulls at a rich setting with a brief full throttle bursts and allow it to cool completely in between runs.
Give it another run and post a video if possible...it's bloody hard to diagnose engine problems with just words..glad it at least runs, I'm sure it's just a case of tuneing.

I've adjusted the stop screw so there's about a 1mm gap at minimum throttle. Would it be better to set it so it's completely closed at minimum throttle?

What's the nva?

I'll swap the front bearing just to be sure it's not causing any issues. I've also ordered a new carb body as one of the screws that hold it onto the engine case had stripped its thread. So I cut a new thread, but the screw used now is too big and I wasn't happy with using it long term.

I'll record the next run, I did think about doing it for this one, so I suppose that would have helped.

Nva is the needle valve assembly, sorry I should have made it clearer.
The way I've always set glows up is with the throttle stick pulled right back it will idle but pulling the trim right back will fully close the venturi and stop the motor.Back that throttle stop screw off and give it another go.

The other thing I forgot to mention is have you run a line from the exhaust nipple to the tank? most glows need a bit of positive pressure to draw fuel.
Glad I only piss around with diesels now!!

Yeah, I've got that. There was some oily residue going from the exhaust back through it slowly, I suppose from when it's been running rich.

It's a long time since I played with oily noise generators - but if the front bearing is leaking, it can draw air into the crank-case, which will affect the mixture, making it difficult/impossible to tune up.
It could also be that the front bearing has been put in back to front, with the dust seal on the inside, not the outside.
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Once you have 'lost' the needle valve settings, it can take days of fiddling and making tiny adjustments, to get it right, because each time you alter one, it affects the other!
If I recall, the easiest way is to get the top end (wide open) right first, with the idle needle way rich, and then you can start tweaking the idle mix needle in - then the top, then the bottom, then the top and round and round!
Then - of course, if you should change the plug - or the prop - or the fuel, that will all affect the mixture settings! [badass]

As for stopping an IC engine an RC carb should be able to completely close the air supply and thus the venturi suction so effectively stopping the fuel flow.
Hence it is common to set the transmitter up with an engine cut off button which drops the throttle channel to zero whereas the throttle stick only goes down to a specific 'idle' throttle setting.

Electric does have 'throttle' advantages.

I sort of agree with Q and Eric however it sounds like squares engine is nearly there in terms of tuneing with just a bit of spluttering between idle and high speed, still think it's a bit rich at idle...or could be a case of simply opening the throttle to quick

Not got a computer tx yet, but not a great fan of electronic trims, much prefer the mechanical tx trims.

Throttle idle speed set ( when tuned ) via full trim, a reliable idle speed being wanted.

To stop engine just apply throttle full down trim with engine at idle ( or throttle full down trim when calling "landing" ) . Just remember not to fully apply closed throttle during landing ( as idle trim removed now ) as a "dead stick" landing will need to be announced .

Slope soarers land dead stick all the time, as someone said.

This action takes half a second...

I presume computer tx has engine kill button that will need to be set up ?

Enjoy...

Ps, you will have seen pilots raising the model nose near to/at vertical with engine running flat out in the pits, ask yourself why...

ALL gliders land 'dead-stick'! (Heli's land abruptly if the engine stops!) :woohoo:
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Rich's comment reminded me - pre computer radio, set your engine to idle reliably with the throttle trim UP, but the throttle stick down, by mechanically adjusting the push-rod. To stop the engine, leave the stick down, but pull the trim down.
Just use the throttle-stop screw to stop the carby barrel from falling out! It's a hang-over from single-channel or reeds days, where it was used to set tick-over speed, because the positioning of the 'servos' used wasn't very accurate.
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If you have a throttle/engine cut button or switch, it is probably pre-set in the tx's programming. all you need to do is decide which way is run, and which is stop! (The button will be press and hold to stop).
With more advanced radios, you can designate which switch does what!

Thanks for the replies.

I'd prefer to use the trim method for cutting the engine, it sounds more reliable than a kill switch. I've set up kill switches for my electric planes, but that's a necessity to avoid accidents if the throttle gets knocked. But I suppose that's not as necessary for a glow engine, and it leaves the switch for something else.

So for the next run, I'll set the barrel to be closed. I'm going to need to jig up a throttle lever on my test stand so I can hold the throttle in position easier.

As a side note, fitted the cleaned and reassembled ME Heron diesel back into the cleaned and serviced 2 channel red glider and ran 6 tanks of diesel thru the engine.

Heavenly smell of diesel fuel !

Any ways it's starts well and I ran it in stages, rich and burpy at first then leaned out and compression adjusted.

Last tank, a small kk tin tank of about 10cc or so, she was "on song" competing with next door but ones strimmer, which was much louder and "in harmony" with the heron.

Next is installing the new radio tx and Rx using Futaba 148 servos hopefully.

Will create thread about radio link t8fb blue tooth UK spec set that comes with 2 RX's.

The 27 meg radio gear will be going into boats.

The fuel used was an old tin of MT D1000.

Will have to make an exhaust deflector so the oil gets diverted downwards rather than upwards over the wing etc..

I won't go into detail here, as it is off-topic, but there are ways of making your electric motor safe without using a switch!