Ready Racing Rapid Response R4 – Dirt Rider Magazine

If there’s a part on modern four-strokes that suffers from variable performance, it’s the carburetors. From bike to bike it seems that even when jetted identically you can still get some confusing results. We’re actually asking a lot of our carbs these days, and if you’re a perfectionist for performance, then the $79.95 R4 could be just what you need. This little billet machined piece replaces a plastic one inside the slide/pumper diaphragm activation pulley on all Keihin carbs less than the newest ’07 and ’08 Honda CRF250/450R and ’08 CRF450X.What it does is connect the throttle’s pulley assembly directly, without any free play, to the accelerator pump rod. This eliminates any initial delay and inconsistency when you hit the throttle. It’s been a trick to just wire the stock plastic piece tight to the activation arm but that isn’t really sano. This piece is how the race teams would do it and it’s that level of trickness that makes a factory bike a factory bike. The R4 is simple to install once the carb access is gained, which varies from bike to bike. Some bikes required taking the carb completely off the bike and others just required tilting the carb sideways. Once installed the fi rst thing we found was that it’s really noticeable on some bikes and on others it hardly makes a difference. On bikes where we had a hard time getting good throttle response, even after fi ddling repeatedly with jetting and fuel screw setting, the R4 remedied the problem. On bikes that weren’t finicky the R4 made less of a change. It doesn’t make more power, it just cleans up the carb performance at small throttle openings and when you get on the throttle hard. So if you have a bog and can’t seem to fi nd the answer, this is a step you need to look into. -Jimmy Lewis