Which 250R frame is best?
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Lonestar updated their frame last year, I'm not familiar with the probs mentioned because I don't have one. Lonestar does make a frame for the YZ426 motor that I belive is based on their 400ex chassis. As far as the motor goes, the YZ makes more power than the crf in stock form. As far as having the motor, all you have to do is come of with about another 10-12 grand for the complete chassis,plastic,etc if you want new. A custom exhaust system will be in order and whatever tinkering you have to do to make the intake match up with the different carb/motor combination. You will also have to adapt the wiring harness from the motorcycle to the quad if you want to maintain the advantages of the TPS carb and 3D mapped ignition which is standard on these motorcycles. If you use a 426 motor, make sure there is room in the frame to get the valve cover off, or you'll have a real bad time adjusting the valves which is a pain the backside on this motor. I would advise the use of priemium clutch components from the supplier of your choice, as the extra traction afforded by two wide tires as opposed to one skinny one places a lot more strain on the drive components. You will also need an external oil tank if you use the 426 unless you convert it to a dry sump(available from Doug Dubach Racing). Make sure that you understand that you need to change the oil very frequently on these motors. The 450 might require less oil changing, as the motor oil is separate from the clutch, but it doesn't hold very much oil.
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I would stick the 450 in the new LRD frame, they should make them to fit that motor. The LRD frame looks and sounds awesome. I have heard it is hard to get a Walsh frame because he only builds a couple a year, and some of them are for him self. I could be mistaken, he may have a bigger inventory now and expanded his production. Go with the LRD man, be ahead of the game.
#20
if you want to run a yzf426, get an aftermarket 400ex frame. i have a buddy that custom fabricates engine mounts just for the 426 for the ex frame. he was in a couple magizines for it. if you want to go that route let me know and i can get ahold of him for ya. he hasnt had a problem with them yet and has been running this setup for a year now, mostly motocross.