How ro replace engine bearings


How to CORRECTLY replace your bearings in  your 2 stroke Glow engine

This project  will be in TWO parts:

(1) Disassembly and parts inspection
(2) Reassembly and test run

NOTE: This project is best viewed with your PC set at 1024x768 resolution

         The project engine will be a Thunder Tiger .61 which began sounding weird on a receint flight. It also has developed a slight clicking sound at top dead center. This indicates that a bearing may have failed or something got through the engine at some point. This engine has had a hard life in my Kyosho Super Stearman running very high RPM frequently. It never ran lean, but it often ran well over 16,000 RPM over and over again.  

         Two Stroke engines are relatively easy to overhaul becuase they have very few parts to contend with. However, these parts are "critical fit" and must be carefully handled. In order to perform an overhaul, the engine must be totally disassembled, thoroughly cleaned, inspected, replace parts as needed, and very carefully reassembled. With any luck at all... you may only need to clean it, replace the bearings and reassemble. Engine bearings should be replaced no matter what, and they are relatively easy to remove. You only need minimal tools to disassemble the engine plus a propane torch. 

If you've never dis-assembled an engine before, there's some specific things you need to pay particular attention to.

WHEN REMOVING THE:

SPECIAL ORIENTATION, MARKINGS, or POSITIONS to pay attention to

BACKPLATE  There's an indentation on the backplate located towards the top of the crankcase.This is critical
HEAD  Mark the head to the crankcase so it goes back on the same as it was. Not crtical though
PISTON & ROD  Mark it,  so it goes back the same way it was originally positioned. This is very critical
CYLINDER SLEEVE  If it doesn't have an orientation pin on the crankcase, mark it so the sleeve  goes back in the exact same location This is very critical
HEAD GASKET  If it has one, replace it with a new one. Not crtical though

         During the disassembly, you may find that the piston sleeve is stuck in the crankcase (very common). Heat up the crankcase jug around circumfrence of the sleeve area. As depicted in photo 1. Gently and carefully grasp the sleeve with pliers and lift it out as seen in photo 2. Do not force it out, add more heat to the crankcase as needed. The sleeve is chrome plated brass and is easily damaged.

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Let the engine cool off naturally, or you may spray the engine with a fine mist of water to speed up the cool down. Do not "dunk" the engine in water or solvents. Mark the rod so you will know which direction it needs to be during re-assembly. Remove the rod & piston by pulling the rod towards you to release the rod from the crankshaft. Then push the rod & piston out the top where the sleeve came out.  

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