small engine through a pickup coil

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Uploaded by: clickersound

Upload date: 1/15/2025

Description:

While trying to get an acoustic recording of my Predator 212 engine, I noticed that if the recorder got too close, there would be a clicking sound, which I almost immediately figured out was the magneto. Once again, I wanted to know what it would sound like with a pickup coil, so I finally got around to recording it along with some acoustic recording. The engine is at idle for most of the recording, but I give it a couple of revs and kill the engine at the very end, sadly without the pickup coil.
The sound of slow revs almost sounds like I just increased the sampling rate of the audio or something, but I promise that was recorded in real time. The only modification I did to the recording was to make the coil part of mono instead of being on the left channel.

You may have noticed that the coil pulses are twice that of the piston pulses, and I'm almost certain that comes down to the nature of this engine being a four-stroke engine. A four-stroke engine gets power every two rotations of the crankshaft unlike a two-stroke which gets one every rotation. I haven't quite learned it either, but most likely what you are hearing is the piston being pushed down for that power stroke.

I need to get a better coil. The one I have now is a cheapy and has a terrible 60 cycle hum with significant overtones that makes notching it out annoying. Most of the yard tools we have are electric, though the leaf blower has a VF drive that is interesting through a coil. I suspect I might also be able to record the lawn mower. It's fuel injected, not carbureted, but it has to make power somehow. I think it always starts on the second pull because the first one is where it builds powers to pulse the injector.

what is that engine, and what does it normally sound like?

oh never mind you did record it acousticly

curious what those engines are used for

I think they're racing engines for gokarts and the like.

Alright responding to multiple comments at once here

So even when the recorder is not connected to the wall you still get the 60hz hum? If you go far outside you still get it? Those are the only two ways I see how you could get a 60hz hum, but correct me if I'm wrong.
A lawn mower with fuel injection? That's an interesting one, although I'm just getting started with small engines. It would make more sense if for whatever reason it's a riding mower or diesel which would likely use a mechanical injection system. You'll have to get a recording of it when you get your better coil. I wonder how those injectors sound.

The engine is a Predator 212 left in the stock configuration. It is a single-cylinder overhead valve horizontal shaft. It can create about 6.5 hp and 8 lb ft of torque with a maximum speed of 3600 rpm. You can actually hear the engine go above that before the governer knocks it back down.
These engines are commonly modified to put out far more power than stock. I've seen people build these things up to 20 plus horsepower by essentially completely rebuilding the engine with stronger springs and the like.
I have just gotten started and am playing around with it, but I probably won't be putting it on a kart any time soon lol, but maybe some day I'll do something. I've had plans to test it as a generator or something along those lines, but I primarily got this to experiment and teach myself how these things work. I got it used and it needed some things tightened up. It apparently looks brand new, but didn't sounded like it had a bad case of piston slap when in fact it was just a loose bolt on the gas tank. When I got the engine, I noticed that things were rather loose and out of place. For instance the airbox was so loose to the point where I could easily turn the nuts with my fingers. The throttle would not spring back because the nut holding everything in place was so tight that it overcame the spring pulling back on the throttle lever. My best guess is that the previous owner was going to build it up and didn't as it had a gokart racing mount on the bottom but you never know. In any case, it runs nicely enough now and I'm learning how everything works.

I think it's intermittently shorting internally. If I position it just so, it stops.

That's so cool.

What pickup coil do you use?

I got it three years ago and I'm pretty sure it was either the cheapest or second to cheapest thing on Amazon that had decent reviews.

Man, not a bad running engine, had quick throttle response too, yeah it definitely went above 3600 by quite a bit, the governor doesn't seem real close on that thing. 

Before I adjusted the throttle stop screw, it would only go to 3600. Since I adjusted it though, it will momentarily go above 3600 before the governor kicked in.