WFO_Pete Posted December 17, 2015 Just wondering, I have an old fourstroke XL250 with a rould slide 32mm Mikuni on it. It uses a air screw to adjust low speed mixture. Now a days 4strokes use fuel screws to do the same thing. Why? Share this post Link to post Share on other sites
KRAYNIAL My Rides (7) Posted December 17, 2015 If it's a pumper carb it has a fuel screw. If it's a non pumper carb, it can have fuel or air. If it's a CV carb, it can be fuel or air. Older carbs do not have separte Main air jets and Pilot air jets. Share this post Link to post Share on other sites
WFO_Pete Posted December 17, 2015 (edited) But why? Since a F/S is located on the intake side of the carb and a A/S is on the filter side; was this done for better throttle response on 4strokes? Not sure what you mean when you said: Older carbs do not have separte Main air jets and Pilot air jets Edited December 17, 2015 by WFO_Pete Share this post Link to post Share on other sites
KRAYNIAL My Rides (7) Posted December 17, 2015 The location of the screw is irrellevant. It's all about the passages inside. Older carbs do not have as many jets as new carbs. Share this post Link to post Share on other sites
