Ok I finally took it to the track for the first shakedown and break-in. The shipment with all the remainin bodywork arrived late on Thursday so I just installed it without the sticker kit and hit the track on Friday
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Now first impressions…I wasn’t able to push it, first because I only did a session to break-in, second because it requires a very different driving style (more on this later)
To sum it up…WOW! I now understand what many people say, this is how karting was supposed to be. I also understand why the old schoolers keep saying it’s the perfect way to learn.
Coming from a KZ, the power is not impressively scary like a shifter, but it’s still a lot and it’s surprising how the package works, it gives you pretty much the same feeling of insane speed, but in a different way. Let me explain. I was on Evinco Reds and during first warm up laps the kart was extremely squirrelly, same as a KZ. It’s a combination of extremely light weight, seat further ahead and high rpm powerband.
As tires warmed up, the kart finally started hooking up, and oh man…it’s fast! The engine picks up revs in a blink of eye, but you need to drive it with surgical precision. As soon as you apply brakes, engine shuts off, all goes silent for fraction of a second, while the rear locks and steps out. As soon as you feel it, you then need to release brakes and apply throttle. If you don’t time it well, it just won’t work right. In a KZ you have ample margins. You can correct a lot of issues with extra braking or applying power or shifting gears. Here there is no plan B.
Once I started getting the hang of it, I felt like I could keep turning laps all day, it’s not as physically demanding as a KZ but compared to a Rotax or X30 you can’t relax for a second, it requires you to be 100% focused all the time and have laser sharp inputs.
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Also…did I mention the engine? I was running a tall gearing and I was supposed to keep it under 12k rpm for few laps for break in…wishful thinking! It sounds.like an angry wasp, picks up extremely fast and keeps going…engine noise past 15k turns metallic, nothing like what we are used to. Intoxicating
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Session recap: started with low jet 1.25 out and high 1.25. Learned that low should be turned in to 1.0 for easy start, then opened up. I ended up at 1.0 low and 1.1 high but I have a lot to learn
Issues: Mychron 4 is not reading RPMs past 15k. Engine keeps pulling while Mychon drops back to 7K.
Does anybody know what could be causing it? Too much noise in the wire? Should I coil it less? See video
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Ok. Sold. I’ll take a dozen.
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Your max RPM setting in the MyChron is set for a KZ, somewhere south of 16k. You need to change that to 20k. It’ll be on the same screen where you select 1x pulse per revolution.
I want to drive it!
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You were right, it was set as gearbox and 14K RPM max, I changed it to 20K and now it works fine.
Based on builder’s input, these are the parameters for a good FA engine
Target max RPM at the end of main straight, to be used as gearing baseline: 19,250/19,500
Then, if you are under-revving in the slow parts of the track, you switch go to shorter gears and hit around 19,750 to 20K.
That leaves some safety margin to avoid pushing the engine to the max, but technically you can, it’s just not worth it
Also, the more I think of it, the more I’m convinced that, together with today’s KZ, this is really the pinnacle of karting.
If I were to start today, on my first kart as teen or adult, I would get a FA/ICA, no doubt.
$500 for the engine - $500 for a chassis - $500 of misc spares and tune up items to make it track ready - for less than 2K you have a missile. The only real downside I see is lack of room for taller drivers due to the seat position far up in the front and the braking system, not as good as the modern ones (I come from IPK, that benchmark is tough to beat)
Speaking of brakes…you can have a laugh at my expense.
I was trying to gauge how much pressure I can put into the pedal…turns out the old OTKs feel super underpowered at first, then the bite comes through pretty quick…especially when you are distracted by tapping the airbox. Ooops
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Welcome to the club pal 
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100’s of that era are just plain bonkers. Incredible racing vehicles in ways that are just not apparent by watching them.
Choke before you brake. Especially if you’re just lapping. Throttle should be open, quick tap then hit the anchor.
On revs, depending on the track you can end up gearing short (for 20/21k) and shut the motor down with choke when it gets to 19k or so….
Thats where it gets interesting in a race…. How often do you want to push it to 20+ to eek out that extra MPH or two. With air cooled you have the extra consideration of melting the thing down too. It becomes a game of chess where your game can be wrecked for no apparent reason 
That’s said, “chasing revs” can be a mistake too, use your best judgement based on data, which I’ve no doubt you would do anyway.
/edit A rotary might not want to pull past 20.
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Very true. I’ve seen guys gear for 18 and less and dominate events.
This is part of the fun and freedom of 100s. It allows different ideas to come to fruition rather than getting forced into a very specific set up. This are these intangible qualities that reward competitiors.
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This stuff is addicting. Speaking of ideas, here is another one. Different valve profiles give you a different output and it’s for sure another tuning variable to mess around within the engine
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I’ve got a lot to learn so I’ll focus on the driving first, but engines are so simple and tuneable it would be a missed opportunity not to tinker with them
Ohhh it’s on now! Just you wait for that thing to get on the pipe with the 30mm slide. Big mid, same or more overrev.
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