[Gabes]

It definitely can make 56-57HP (or more with some major tweaks) and a lot of info can be found on this web Also check my showcase...

Thanks very much for the reply and info! What costs were involved with making that power? Power only - what mods would you need to match your figures?

 

[Gabes]

The engines are designed to meet worldwide LAMS/A2 regulations. Everything about their design -- valve diameter, timing, lift, duration, port volume, runner length, compression ratio, fuel delivery, exhaust design and rev limit -- were spec'd to meet those numbers, as well as delivering a smooth and torquey power curve where the majority of riders of the class actually need it.

There's an old hot-rodder maxim that goes something like "horsepower is in the heads." This mostly applies to this engine too though the low compression ratio (10.7:1) and low redline (8500?) put a bit of a damper on how much you can get: A low rev limit means if you open up intake runners and ports and put an aggressive cam grind in it designed for 12-13K RPM you won't be able to use them to their fullest and you'll hurt low-end performance. If you could raise compression to something closer to 12.7:1 you might see a 6% or ~3HP increase; without bumping the static compression you're leaving that on the table.

The engine is basically a "square" design -- it's bore and stroke are virtually identical. The 67mm bore is pretty small for a "big" twin (and MT07 has an 80mm bore) which constrains valve size. RPM is not limited by valve-springs; with a 66.8mm stroke the mean piston speed of the CBR500R at 8500RPM is the same as a CBR600RR at 13500RPM. In other words, even if you put a desmodromic valve control set up in a custom head, you'd still not be able to rev it out without going deep into the bottom end to install exotic parts.

That bore size -- the same as the CBR600RR -- would be fine if the cam/port/runner design flowed a ton at high RPM like a 600RR and the engine could spin that fast, but they don't and it doesn't.

Anyway, major choke points for power is basically in the head, the compression ratio and RPM limitations, not the tune. If you want 55-60HP from this engine you're going to need to spend a fair chunk of money to get it. IMO it would make more sense to put those funds toward a new bike -- CBR650R, SV650, MT07 etc -- and leave this one intact for another A2 rider.

Thanks for a very in depth reply, some interesting stuff for sure!