My old XR build info: The TTR has become the new choice for a thumper to race in endurance events but for me the XR was our flagship race craft. I started developing an XR platform with Peter K. back in 2010 when we attended our first 24/hr race. We spent about 2-1/2 years figuring out exactly what we could use and not use for racing that would not only make the bike fast and competitive, but also last a full 24 hour race. After putting our heads together, racing many endurance races for trial and error, we came up with the list of changes below. We obviously didnt create a masterpiece but it was pretty damn fast and worked well. I changed displacement 3 times and the bike itself changed wildly between chassis mods, suspension choices, brake setups, etc. Since Im a geek about sharing our setup info I thought I would post up what I remember from the bike that worked so well. This is the list of mods and setup info that applies to the XR as it sat when we won our class and took 2nd overall in the 2012 24/hr race. The benefit here is that these mods are still legal and are proven to work. Bike: 2003 CRF100 (XR100) Engine: -Stock bottom end -Clipping Point 115cc cylinder and piston -Clipping Point Superhead and race cam. -Much larger intake and exhaust valves then stock. ***NOTE*** BBR makes a 120cc kit for this motor but its designed for dirt riding. It gives much more midrange but not much else up top. You got about a 30-40% gain in horsepower. The 120 kit was good for about 9-11hp With the 115cc kit you can double your horsepower. Stock hp rating on the XR is about 7hp. With the Clipping Point head we received between 14-16hp with regular 91 octane gas. The bike is heavier than a KX65 but can match the bike in acceleration and top speed with this kit. It is actually faster because the XR ran 17s and ultimately has a higher top speed with that added advantage. -High flow oil pump ABSOLUTE MUST WITH AFTERMARKET HEAD -External oil cooler. (Oil line taps provided by aftermarket cylinder and head) Another must if you run the aftermarket head. Excess heat will destroy the performance of the bike as well as prematurely wear the piston rings. Oil cooled motors only make power if they stay running cool. -Retained kickstarted on motor to facilitate quick restarts after a crash. -26mm Non-CV Mikuni Carb. Stock intake boot -Uni pod filter for filtration. Used to gain room for rear shock mostly. Exhaust: -BBR Exhaust (no longer in production) **NOTE** Weve just recently learned the BIG GUN exhaust system does not work with the Clipping Point top end. Do not purchase that exhaust if you have one. Chassis: -Stock frame with nominal mods to fit upgrades. -Frame slightly modified with oil cooler mount. -Subframe slightly modified to fit rear shock reservoir -Top mount for rear shock custom fabricated to accomodate sportbike shock (much shorter overall) Front end: -1986 Honda CR80. Triples/forks/wheel hub/brake master/caliper -Lowered 5 internally using spacer above top-out spring. -Single compression hole welded shut in each dampening rod. -15wt oil -Standard sized mini bike dirt bars used -Bark guards used to protect brake and clutch levers during a crash Rear Shock: -2004 ZX10R rear shock. (only used because it was laying around) -Stock internals for shock. Chassis modified to fit rear shock and provide as much ground clearance as possible with stock uni-link cradle. Swingarm: -Stock swing arm -Modified at one point to allow for direct shock mounting. Not used during race. Wheels: -Excel aluminum 17 x 2.5 rims front/rear Tires: -Bridgestone 125GP slicks 90mm front/rear in super soft compound The biggest problem we faced with the XR platform outside of power-to-weight was ground clearance. I spent a lot of time just trying to find clever ways to keep the foot pegs from scraping the ground each corner. After a few failed attempts at raising the bike up to supermoto height, we settled on maxing out the rear with the stock cradle then keeping the swapped front end as tall as possible without loosing grip on the front tire. The reason why this bike was valuable to us was simple. There are millions of them out there and parts were very cheap. The XR motor is rock solid reliable and you can find a wide range of performance parts for the engine. Its even used in the NSF100 chassis so you can find tons of parts. This bike is still alive and kicking. You can talk to Peter at Nkb Motorcycles if you want to take an up close look.
Posted on: Fri, 06 Jun 2014 15:51:48 +0000
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