The CBR250R's balance shaft wasn't designed to quell vibration with a larger piston. It would likely be more vibration prone. A big bore will increase torque, but will probably only marginally increase horsepower. Based on my experience having sampled an Athena kitted 166cc big bore Honda CBR125R - the bike had tons more torque, and could cruise easily at a higher topspeed - this part was great. But the bike showed much more vibration in the upper rev range to the point where I was concerned that the bike might vibrate apart (I never came close to bringing it to redline for this reason). As a result, the kit really mellowed the bike out - I felt I had to ride it like a low redline, high torque, V-twin cruiser which took something away from the high revving nature of the bike and robbed it of its stock character. Based on this experience, I felt the roughness just wasn't worth the additional power and torque to me. Either way - this would be a concern for me.So... do you think we will see some Big Bore Kits in the near future?
I'd love to see an increase in the displacement and would do it in a heartbeat.
Now if the material the stock piston is made of is heavier then aluminum they could potentially make it the same weight. I guess we will have to wait and see.The CBR250R's balance shaft wasn't designed to quell vibration with a larger piston. It would likely be more vibration prone. A big bore will increase torque, but will probably only marginally increase horsepower. Based on my experience having sampled an Athena kitted 166cc big bore Honda CBR125R - the bike had tons more torque, and could cruise easily at a higher topspeed - this part was great. But the bike showed much more vibration in the upper rev range to the point where I was concerned that the bike might vibrate apart (I never came close to bringing it to redline for this reason). As a result, the kit really mellowed the bike out - I felt I had to ride it like a low redline, high torque, V-twin cruiser which took something away from the high revving nature of the bike and robbed it of its stock character. Based on this experience, I felt the roughness just wasn't worth the additional power and torque to me. Either way - this would be a concern for me.
Mike
yeah its called a Ninja 300.So... do you think we will see some Big Bore Kits in the near future?
I'd love to see an increase in the displacement and would do it in a heartbeat.
my whole reason for buying mine was the great gas mileage,CBR250R 305cc Big Bore Kit
Sendler had posted about this in the CBR500 thread, but I figured it would be useful to have it in this thread for obvious reasons. I'm thinking kit + fuel controller + exhaust + dyno tuning = a lot of money to spend on a $4k 250cc bike. The question is would it be worth it? Anyone have thoughts?
Yup, and cheaper. As a commuter, I can't get over 75mph without looking around for police lights, so I went with lower gearing instead. Guess what speed peak power hits at now. It starts with "seventy" and rhymes with... "seventy-five miles per hour". The rear wheel torque is night and day difference over stock. Immediate pull in all 6 gears at any speed. No pussin' around. For a BBK, I'd think you need not only the kit, but a big valve header, high-flow pipe, fuel controller, and a custom map from a dyno, You could spend over 25% of the cost of the bike modding it when there are used 600 supersports out there that would still mop the floor with a maxed out 250... stock.There is other ways to make power than a big bore.
To maximize the effect of a big bore kit, I wonder if a larger throttle body would be desirable. Maybe the 305 cc displacement is within the stock throttle body air flow capability to feed the motor? Back in the day, many big bore kits included a larger carb, to flow more air/fuel mixture.... For a BBK, I'd think you need not only the kit, but a big valve header, high-flow pipe, fuel controller, and a custom map from a dyno...
we don't all live in caliyou don't need a big bore kit go to www.jetttuning.com John Ethell can get the same power w/250cc's he did on my bike![]()
true, if you live in the West (i used to have a VFR750, bought it for $1,000). here in India, however, any affordable used bike on the market is gonna be 150cc max. if it's as old as my VFR was, probably more like 100cc.You could spend over 25% of the cost of the bike modding it when there are used 600 supersports out there that would still mop the floor with a maxed out 250... stock.