Alright folks, let me tell you about this crazy project I just wrapped up. The goal? To see if I could actually get a small motorcycle engine screaming at 20,000 rpm. Sounds insane, right? Well, buckle up.
It all started with a beat-up, old 125cc two-stroke engine I snagged for next to nothing. First thing I did was tear that thing down to bare bones. I’m talking every single nut, bolt, and bearing. I needed a clean slate to work with.
The challenges were obvious:
- Balancing: At those speeds, even the slightest imbalance would tear the engine apart.
- Lubrication: Keeping everything cool and oiled at 20k rpm is no joke.
- Fueling: Getting the right air/fuel mixture in that short amount of time… tricky.
- Vibrations: Oh man, the vibrations. I knew I’d have to beef up the engine mounts.
So, I started with the crankshaft. I took it to a specialist who knew his stuff and had him dynamically balance it to within an inch of its life. Cost me a pretty penny, but it was essential.
Next up was the cylinder. I ported and polished the heck out of it to improve flow. I also had the head modified for better squish and combustion chamber shape. Every little bit helps, right?
For lubrication, I went with a high-end synthetic two-stroke oil and upped the oil injection rate. I even considered pre-mixing the fuel, but decided against it for now.
Fueling was a nightmare. The stock carb was never going to cut it. I ended up slapping on a bigger carb with a modified jetting setup. It took a lot of trial and error, but I eventually got it dialed in… sort of.
The ignition system also needed an upgrade. The stock ignition timing was way too conservative. I installed an aftermarket CDI unit that allowed me to adjust the timing on the fly.
Then came the moment of truth.
I bolted the engine onto a test stand, hooked up the fuel and oil lines, and fired it up. It sounded… angry. Really angry. I slowly started increasing the throttle, keeping a close eye on everything.
5,000 rpm… 10,000 rpm… 15,000 rpm… the engine was screaming. Vibrations were intense. I could feel them through the entire test stand.
And then… bang!
Something let go. I quickly shut it down and inspected the damage. Turns out, one of the connecting rod bolts had snapped. Lesson learned: use high-quality hardware, folks.
I replaced the bolt with a stronger one and gave it another go. This time, I made it all the way to 20,000 rpm! But only for a few seconds. The engine was definitely not happy. It was running super hot and felt like it was about to explode.
So, did I succeed?
Well, yes and no. I got the engine to hit 20,000 rpm, but it wasn’t sustainable. It was more of a proof-of-concept than anything else. The engine would need a lot more work to be reliable at those speeds. Things like a custom connecting rod, better cooling, and maybe even a different fuel.
But hey, that’s what makes these projects fun, right? It was a wild ride, and I learned a ton. Maybe one day I’ll revisit this project and build a 20,000 rpm monster that can actually last more than a few seconds.