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| When KTM introduced there first 250 four stroke in 2002 they based it on the same bike as the 400 and 520. Not that these bikes where bad in fact they where great bikes. The problem was the 250 weighted the same as the 400 and 520. This did allow KTM to test the waters so to speak and find that there are riders out there that wanted a 250 thumper. In 2005, KTM introduced the RC4 motor in the 250SXF. This was a new bike from the frame up. It no longer shared any thing with its bigger brothers. This bike was light, fast, and showed to have a much more reliable valve train than the other 250F’s on the market. Then in 2007 they released the XCF. Now KTM had a Moto Bike and a Woods Bike based on the RC4 motor. Early in December 2006, we got our 2007 XCFW250. In our very first testing, we found that this was a great little bike it made great power and handle like a dream, it had the “E” start button great looks what else could you want?? A bike that is great to start with makes our job harder unlike the old DR’s and XR’s of the past that had a lot of room for improvement this bike was very good out of the box. Russell and the guys in the shop went to work, first we disassembled the motor to see what we had to work with. Looking at the cylinder, we found that there was room to install a sleeve that would allow us to have a 82mm bore. To do this we worked with Advanced sleeve to develop at sleeve that was thin yet strong. They built us a sleeve from their DUCTILE 100-70-03 material. This material is the same we us on the Honda CRF270 kit and has proven to last has long if not longer than Nickasil Plated cylinders. Not only dose it have a long life it is very strong and has great heat dispassion properties, so we had the sleeve and WISECO built us a piston from a new forging that they developed just for this motor. The end product was a very light and strong piston that in our testing has excellent piston life. Our first test motor had over 50 hours of testing and the piston and cylinder was still within specs. So how did it all work? The 300 motor had huge bottom and mid power and would still rev a quickly as the stock motor. That is just what we wanted. This made the 250 much better in the woods and trails. Before you had to rev the 250 to get any power ride it much like a 125, with the 300 kit you can use the bottom end of the power curve and ride it more like an open class bike. We tested two different compression ratios 12:1 and 13:1. With the 13:1, the power is just bit snappy, great for the racer but not be the best thing for the causal trail rider. The 13:1 motor also needs 100-octane fuel. The 12:1 motor will run on pump gas and the power is a bit smoother and for most will be the best choice. If you have any question please guy our tech guys a call they will be happy to help you chose the right kit for your needs. |
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