CLICK ON THE PICTURE TO THE LEFT TO SEE APPROX MEASUREMENTS * * * THE MEGA CAM SEEMS TO WORKS FINE WITH MOST XR50 CRF50 XR70 CRF70 TRX90 AND LIFAN HEADS THAT USE THE HONDA TYPE CAM SHAFT. IE LIFAN 120CC & 138CC ENGINES. BUT !!!!!!!!!! WITH SOME HEADS YOU NEED TO BE CAREFUL THIS CAM HAS SO MUCH LIFT AND DURATION THAT YOU NEED TO MAKE SURE THE VALVES DON'T HIT WHEN PASSING EACH OTHER,, AND THAT THE VALVE SPRING DON'T BIND OUT COIL TO COIL. I HAVE HAD TO ON SOME HEADS GRIND OFF THE OUTER EDGE OF THE VALVES SO THEY CAN PASS EACH OTHER. IF COIL BIND IS A PROBLEM , USE OUR 200149 SET OF WIDE COIL VALVE SPRINGS. (TRX90'S AND LIFAN 120CC WON'T HAVE BINDING PROBLEMS SO USE THEIR STOCK SPRINGS.) BUT WITH THE LIFAN 128/138 YOU WILL NEED THE 200149 SPRINGS MEGA_CAM @ e HEAVY_DUTY VALVE_SPRINGS WITH_WIDER COIL_SPACING FOR_HI_LIFT_CAMS IN_50_70_HEADS (GREAT_STOCK_REPLACMENT) (S1129) ALSO WORK TO REPLACE STOCK 50 AND 70 STOCK SPRINGS AND ADD SOME MORE TENSION S1129 @ *28_TOOTH CAM SPROCKET FOR THE OEM HONDA TYPE BEARING CAMS 14321-GBG-900 1/22A (200025)THIS IS FOR CRF50 CRF70 TRX90 STOCK TYPE CAMS THIS WORKS ON THE LIFAN 140CC ENGINES IF YOU USE A HONDA TYPE 2 BOLT CAM 200025 @ *32 TOOTH_CAM SPROCKET FOR STOCK HONDA_BEARING_CAM AND Z28 OR MEGA CAMS (200156)This cam shaft sprocket will allow you to run any Honda bearing cam with your LIFAN monster engine 120CC 138CC OR 140CC that requires a 32 tooth cam sprocket. These engines will usually if not always have a 78 mm tall cylinder. 200156