HPI Racing Nitro Star engine has composite body rotary valve carburetor with 5.5mm bore with silver colored cooling head. SG (pilot) type crankshaft. Specs: High Speed Needle Setting: Turn clockwise in 1/8 turn increments to lean fuel mixture. Do not exceed 2-1/2 turns from flushIdle Adjustment: Adjust for about 0.04" (1mm) gap between slide valve and carb body at bore openingLow Speed Needle: No adjustment recommendedDisplacement: .18 cu in (3.0cc)Distance Between Mounting Holes Same Side: 0.43" (11mm)Distance Between Mounting Holes Opposite Side: 1.22" (31mm)Height/Bottom Mounting Flanges to Top of Cylinder Head: 2.99" (76mm)Height/Bottom of Crankcase to Top of Cylinder Head: 3.5" (89mm)Length from Pull Starter to End of Crankshaft: 4.13" (105mm)Length from Pull Starter to Front Bearing: 3.3" (75.3mm)Length from Center of Crankcase to End of Crankshaft: 2.96" (75mm)Diameter of Carburetor Bore: 0.21" (5.5mm) Requires: Fuel: Car blend with 20-25% nitro contentMisc Items: Fuel tubing and track equipment