90 degrees crank
 

easy now CBR family. was thinking last night about making the F3 into a cross plane by turning crack 90 degrees.
has any one done this

Why do you want to do this?

Balancing the engine would be awkward and you'd have to completely rejig thevignition to get sparks in the right places.

Why? You’ve been mis-informed. Read up on differences between cross vs. flat plane cranks here:

https://www.motortrend.com/how-to/di...-plane-cranks/

https://www.enginelabs.com/news/vide...inder-engines/

To get cross plane crank in F3, you’d need to:

1. Cut crank into 4 pieces

2. Rotate journal for #2 rod 90-degrees, #3 270-degrees, #4 180-degrees

3. Re-weld crank back together

4. Grind custom cam-shafts for new crank timing

5. Re-program ignitor for new crank timing, or install aftermarket programmable ignition

6. Custom exhaust


In end, you’d make exact same amount of power and bike would be just as fast. So why???

Have to go back in history to “Big Bang” 2-stroke engines of 500 GP bikes. They had so much power that wheelspin and high-sides coming out of corners were common. Difficult to control monsters! They discovered if you group the ignition of cylinders closer together, rather than being spaced evenly apart, that there’s more traction coming out of corners. There’s still disagreement on why this is so because power & torque output is still same.

With migration to 4-strokes, “Big Bang” was forgotten because these newer bikes were heavier, weaker and slower. Smoother powerband was easier to control. But after a decade of R&D, 4-strokes doubled power output and again had same control issues of traction and highsides as earlier 2-strokes. Cross-plane Big-Bang engines came back as way to tame the slide on exit of corners.

So.. unless you’re having problems with F3 sliding out of corners under WOT and highsiding you all the time, why???

Inline-4 crank same as V8, leave out cylinders 5-8.
https://cbrforum.com/forum/attachmen...1&d=1716669574

On a 2 stroke it's easy, big bang vs screamer - it's a 360 degree cycle where you either get 2 bangs every 180 degrees or one bang every 90 degrees but on a 4 stroke its a 720 degree cycle and makes very little sense outside of motogp.

The standard configuration gives you a bang at 0, 180, 360 & 540 degrees - nice and even. Put the cranks crosswise and you could be talking 0, 90, 180, 270 then nothing until 720 or 0, 90, 540, 630 or 0, 180, 430, 610 or ... - all vastly unbalanced.

A hell of a lot of work for a vibrating mess of an engine.

Thank you all for replying on this topic:
wow 1st of all I have learned a lot and yes upon reading it is pointless, they is a lot more to it than I thought to be honest.
I thought hmmm Al cross plane my CBR thinking I only need to take crank out and adjust to 90 degrees hahah but no that's not the case.
When I have turbo manifold and plenum made i am going to turbo the F3 and thought making it a cross plane will help, but it's a job on its own doing turbo conversation and then I question doing that as it's only a 600.

​​​​​​Thanks again CBR family stay safe out there, burn rubber not the sole.

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Ah TURBO!! So much fun and wild power!!!

Would love to follow your progress on that! Here’s guy that converted his Ninja 250 to EFI. Then added TURBO! Then made his own dyno to tune it! :eek:
Swarfman64 project log: Ninja (EX250) turbo project

Don’t do Ecotrons, crap low-end stuff and non-existent support. Use Microsquirt instead.