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8. CYLINDER/PISTON

8-0

Mongoose/KXR 250

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CYLINDER /PISTON

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SERVICE INFORMATION -------------------------------------------- 8- 2

TROUBLESHOOTING ------------------------------------------------- 8- 2

CYLINDER/PISTON---------------------------------------------------- 8- 4

Summary of content (9 pages)

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8. CYLINDER/PISTON Mongoose/KXR 250 SERVICE INFORMATION GENERAL INSTRUCTIONS • The cylinder and piston can be serviced with the engine installed in the frame. • After disassembly, clean the removed parts and dry them with compressed air before inspection. TROUBLESHOOTING • When hard starting or poor performance at low speed occurs, check the crankcase breather for white smoke. If white smoke is found, it means that the piston rings are worn, stuck or broken.
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8. CYLINDER/PISTON Mongoose/KXR 250 SPECIFICATIONS Standard (mm) Service Limit (mm) I.D. 72.705_ 72.715 72.8 Warpage æ 0.05 Cylinder Cylindricity æ 0.05 True roundness æ 0.05 0.015_ 0.055 0.09 Ring-to-groove Top clearance Second 0.015_ 0.055 0.09 Top 0.15_ 0.3 0.5 Ring end gap Second 0.3_ 0.45 0.65 Piston, piston ring Oil ring 0.2_ 0.7 0.9 Piston O.D. 72.67_ 72.69 72.6 Piston O.D. measuring position 10mm from bottom of skirt æ . Piston-to-cylinder clearance 0.010_ 0.040 0.1 Piston pin hole I.D. 17.
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8. CYLINDER/PISTON CYLINDER/PISTON Mongoose/KXR 250 Gasket Cam Chain Guide REMOVAL Remove the cylinder head. (Refer to the chapter 7) Remove the two dowel pins, cylinder head gasket and cam chain guide. Dowel Pins Screw Cylinder Unscrew the clamp and disconnect the water hose. Remove the cylinder Water Hose Gasket Remove the cylinder gasket and dowel pins. Clean any gasket material from the cylinder surface. °ØBe careful not to drop foreign matters into the crankcase.
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8. CYLINDER/PISTON INSPECTION Inspect the piston, piston pin and piston rings. Remove the piston rings. °ØTake care not to damage or break the piston rings during removal. Clean carbon deposits from the piston ring grooves. Inspect the piston wall for wear/scratches/damage. If any defects are found, replace the piston with a new one. Install the piston rings onto the piston and measure the piston ring-to-groove clearance. Service Limits: Top: 0.09mm replace if over 2nd: 0.
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8. CYLINDER/PISTON Mongoose/KXR 250 Measure the piston pin O.D. Service Limit: 16.96mm replace if below Measure the piston O.D. °ØTake measurement at 10mm from the bottom and 90° to the piston pin hole. 10 mm Service Limit: 72.6mm replace if below Measure the piston-to-piston pin clearance. Service Limit: 0.02mm replace if over CYLINDER INSPECTION Inspect the cylinder bore for wear or damage. Measure the cylinder I.D.
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. CYLINDER/PISTON Mongoose/KXR 250 PISTON RING INSTALLATION Install the piston rings onto the piston. Apply engine oil to each piston ring. °Ø• Be careful not to damage or break the piston and piston rings. • All rings should be installed with the markings facing up. • After installing the rings, they should rotate freely without sticking. Top Second Side Rail Oil Ring Side Rail Measure the connecting rod small end I.D. Service Limit: 17.
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8. CYLINDER/PISTON Mongoose/KXR 250 “IN” Mark °ØBe careful not to drop foreign matters IN PISTON INSTALLATION Remove any gasket material from the crankcase surface. into the crankcase. Install the piston, piston pin and a new piston pin clip. °Ø• Position the piston “IN” mark on the intake valve side. • Place a clean shop towel in the crankcase to keep the piston pin clip from falling into the crankcase. CYLINDER INSTALLATION Install the dowel pins and a new cylinder gasket on the crankcase.