[Dotini]

Howdy, CBR250R fans!

I'm a retired Boeing engineer who's raced cars and karts since the 60's. My motorcycling has been mainly touring on a Suzuki Bandit, with excellent memories of rides to Yellowstone and San Francisco, camping along the way and 0% on freeways.

My interest in the CBR250R is learning about its durability and weaknesses in high speed operation, then adapting maybe 3 of the engines to road racing kart application. I want to start a new class for 4-strokes. I might buy wrecked bikes for this, and have my eye on one already.

One thing I know already is that I will have a problem with gearing. With a 15 tooth drive sprocket, I will need an 11 tooth sprocket on my kart axle to achieve the same speed I do with my CR80 kart, which typically runs with a 21/24 front and rear. 10,000 rpm versus 13,400. So I will want a larger sprocket for the engine if it will physically fit. I may have to weld it off the side of the stock sprocket if it won't clear the case.

Another very important question I have is the weight of the CBR250R engine. Anyone know?

I will be very grateful and appreciative of your help.

Respectfully submitted,
Steve

 

[TheoR]

Hi,

The engine used in the CBR250R is a relatively new engine design, I believe introduced for the first time in 2011, so the real long term durability is not really known at this time, unfortunately.

However, there are lots of people on here who have put on quite a bit of miles in the 1 year period, so I think the engine is pretty stout.

As for high speed operation, this is a single piston engine so it really likes high revs, as in 10K RPM range.

 

[TX_Dj]

Honda wouldn't release the bikes (CBR250R, CRF250L, both using the same engine) unless they were going to hold up in the real world.

As for adapting for karting use, these engines are only about 22 HP, only about 17 ft-lbs torque, but they have a nice wide powerband with good torque up to 6500 rpm, and horsepower pulling strong to 8500-ish.

With the smaller tires of a kart, and weights similar or less than the original bike, picking a rear sprocket that gives you the max speed you'll need for the straights would be best, I think. I'm sure you already know that, though.