462cc +4 bore cylinder works cylinder, +4 Hotrods crank, High compressioin CP piston (The old VCP 14.25:1 piston from Venom with slight modifications bringing it down to 14:1)
Custom Web cams, +1/+1 Ferrea valves, all from CFM Motorsports, Kibblewhite springs
FCR 42.5 with the carb to head boot from a 05 TRX 450R, the intake is a Fuel customs intake for a carbed YFZ, and it has been shortened about an 1.5"
The head is a +1 head from CFM Motorsports, which is in bad need of an update. The airflow is not on par with with my current heads
Barker Full System
Dyna Programmable ignition box, curve #1,
Stock coil, CR8E
Big heavy 20" Duro street tires on steel rims. (only non knobs I have sitting around)
13/38 JT sprockets, RK X ring chain
Watch for updates, as I don't think I'm finished with this yet. I tried a lot of different cam and intake combinations before landing on this one. It's been as high as 59hp, but it gave up too much torque. It's been as low as 54 hp with a little more torque than this, but this was the best compromise, averaging the most power.
The intake cam is very close to a Megacycle X-5, but it's timed different. The exhaust cam is a Web 539. I had a FCR 41 and a FCR 42.5 on during this testing, and the 42.5 was marginally better. I wouldn't be afraid to skip the carb boring if you found a 40 or 41 for this setup.
The biggest changes to the curve were actually with the variety of intakes. I started with a Honda TRX 450R boot from an 04/05 model. It wasn't bad, but the length was a little out of sync with what the engine wanted. I remember from when I put it on, that it felt like a big improvement over the 400EX boot that I had on there prior. I did not have it on the dyno at that time.
Don't be afraid of a foam filter. The K&N style filters did allow for a change in the main jet, so there is a difference in airflow, which I knew, but that didn't translate to more power on the dyno. When I switched to the FCI intakes, it really didn't make more peak power, but it did make more torque in certain areas where the intake was in tune. The intake itself was responsible for the changes, due to the changes in resonance tuning. The filter had little to nothing to do with the changes.
You can still see a slight dip in the torque curve. There were 3 of them, and they were worse, when I started with the full length version of most of the FCI's, and with the Honda boot. Intake resonance tuning is simple, but complicated. If you have ever slapped your hand over the end of a pipe and heard the sound, that's basically what is happening in the intake. That pressure wave bouncing back and fourth can have advantages and disadvantages to the engine, based on when the wave gets back to the valves. So in certain parts of the rpm range, it will help, and in certain parts, it will hurt.
The longer the intake, the lower the frequency, and the lower rpms where the effect will be helpful. The opposite is also true. So first I found the FCI that was the closest to right, which was the one for an early YFZ. It's also a nice fit in the chassis. I cut a half inch off of the carb side, and tried it again. It improved. The peaks in the torque moved up in rpm, and started filling in the dips. I cut another half, and it followed the same trend. I cut another half inch, and The only dip left is still shown in this curve, and it's half as deep, if that.
This ended with a really great, usable curve for just about anything. 40 ft lbs of torque is huge from a 462, and when you drop the clutch on a start, you have that monster torque to keep you from dropping below the powerband, or to keep you from having to down shift when you climb a big hill. Even with all that torque, it still pulls hard all the way to the limiter, and when you shift, the shift drop puts you right in the heart of that other bump in the torque curve around 7500-8000 rpm
As I said, in the beginning, watch for updates. The head on this is from a long time ago, and it is not on par with my newer stuff. I will be making changes to the head when I can find the time. I think this thing can see 60 hp.