This quote is from the “David Klaus from Briggs Racing - What is WRONG with karting?” topic in general - but I think it fits better here, and I’d thought I’d add an update (at least from my research) on this topic…
I couldn’t agree more, and concur with David’s points. And I’m impressed with how well that 206 program has worked.
I had somehow missed that entire thread early this year when I joined, and just read it the other day, which is interesting because it’s exactly what I’ve been thinking and doing research into. What should be next after 206, at least from currently available commercial products?
The goal of course of this is not to find the fastest possible engine. Those already exist and are great for youngsters trying to move up series. Instead, here are some of the considerations I was trying to find an alternate low-maintenance engine to meet for the rest of us:
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Something fun that is just (or at least nearly) as easy to run / maintain as a 206. Change the fluids at the start or end of the season, check safety items and fluid levels before each race, add gas and go have fun.
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A 4-stroke engine. As David said, mixing oil precisely with expensive leaded fuel, changing plugs, jets, and reeds isn’t a great selling point for most people, so something that runs on pump gas is a big plus. Plus a 4-stroke allows for a wider powerband so missing a shift isn’t a race killer. More torque is also great for those that are a little more - robust.
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Gears with a clutch that is forgiving.
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A starter is highly desirable (at least by me) so when you kill it on the grid (or after a spin), no big deal!
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A major manufacturer with good parts availability and dealer support is a given - so something current is preferred.
So, after a few months of research, here is my top pick, and what I’ll be working with this year - the Kawasaki EX400, the engine from the new 2018 Ninja 400 streetbike. It’s actually somewhat between a 125 and 175 peak power-wise, so that’s the class I’d run with.
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It’s should be easy to maintain with LONG service intervals on internals, as in several seasons I would expect, beyond the oil and filter.
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A newly designed light-weight (for a 4-cycle) 399cc parallel twin with fuel injection. It has a semi-dry sump (a dry sump setup with the tank inside the case) - so oil pickup should not a problem. And of course it runs on common pump gas, although 91 or 93 (altitude dependent) would be recommended for track use. And hey, with that no leaded fuel fumes and with the stock cat and muffler it’s 50 state emissions compliant and should meet all track volume limits!
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A six speed close-ratio gearbox with a slipper clutch (slips when downshifting when the engine is much slower than the wheels), as well as assist (to lock in the clutch for less required clutch pressure).
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Starter - check! Combined with a lightweight lithium battery that can also power the mychron. Oh, and an alternator to keep it topped up!
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Kawasaki, a leader in current lightweight street sport bike engine design, with this engine being the baby and the H2R being the top dog.
Of course, getting the local race series to allow me to run it in an open, non-scored class is currently a sticky issue due to insurance regulations limiting displacement to 250cc due to 30 year old provisions. That’s rather nuts when they do allow twin 250’s that make 100 HP, but not something like this. Hopefully we can get past that soon enough so I can give this a good wringing to see if this is a good choice for 4-stroke karting to evolve and grow beyond the 206.
Another initial obstacle will be getting 428 sprockets made (520 is stock), probably in the 19t size to start with, as I have to order a lot of 100. And then fabrication of the engine mount, shifter mount, and clutch (easiest) along with all the other wire harness and packaging details.
Some of the raw specs:
Description: Twin parallel cylinders – 4 stroke
Bore: 70.0 mm
Stroke: 51.8 mm
Displacement: 399cc
Valve train: DOHC, 4 valves per cylinder
Compression ratio: 11.5:1
Lubrication: Semi-dry sump with pump and squirters
Ignition system: TCBI with digital advance
Transmission: 6 speed gearbox with wet assist and slipper clutch
Cooling system: Liquid (water with water wetter for racing)
Starter: Push Start
Fuel System: DFI with 32mm throttle bodies (2)
Max Power: 45 Hp @ 10,000 rpm
Max Torque: 28 Ft/Lb (37.9 Nm) @ 8,000 rpm
Max Rpm limit: 12,500
Weight: ?? Lbs
For reference, the new IAME X30 super shifter:
Description: Single cylinder – 2 stroke
Bore: 63.90 mm
Max Bore: 64.26 mm
Stroke: 54.40 mm
Displacement: 174.46cc
Ports: 5
Inlet system: Reed valve
Lubrication: Oil mixture
Ignition system: Analogical
Transmission: 6 speed gearbox
Cooling system: Water
Starter: Push Start
Carb. Model: HB-15A Tillotson
Max Power: 49 Hp @ 13,000 rpm
Max Torque: 27 Nm @ 12,500 rpm
Max Rpm limit: 14500
Weight: 85 Lbs