How To rebuild a DLE 55 cc engine

In the next few days I will complete the rebuild of a DLE 55cc engine after a crash. The only visible damage to the engine is a broken cooling fin and the throttle shaft was sheared off from the carburetor. The plane crashed nose first from a high altitude so even if the shaft looks straight without x-ray or other methods I cannot tell if any microscopic fractures are developed due to the crash.

WARNING:  The following procedure assumes that you have some experience disassembling and assembling engines. If you have not done this operation before seek help from an experience air-modeler who have worked with this type of engine. Also, by disassembling the engine you most likely voided the warranty.

The following parts except the carburetor are replaced as a precaution and probably not absolutely necessary. Due to reasonably priced DLE parts I decided to replace the following parts.

• Complete crankshaft (includes connecting rod) for $39.99
• Both main roller bearings (front and back) for $9.99
• Walbro carburetor due to broken throttle shaft for $39.99
• Gasket set for $5.99
• Screw set for $5.99
• Woodruff Key for $1.49

DLE 55 parts after disassemble and clean

Cylinder and carburetor are removed.

 DLE 55 Gaskets (bottom left gasket not part of OEM gasket set)

The circular gasket is custom made and goes between the carburetor

 and Troy Build Models (TBM) Small Velocity Stack.

Use a pulley extractor to separate the propeller hub from the crank shaft.

From Top clockwise: Reed valve gaskets, Reed valve spacer, spark plug, piston pin retainer clips and reed valve.

1. Remove the spark plug.
2. Remove the 2 bolts holding the carburetor and reed valve assembly. Probably the gaskets between the carburetor, reed valve and engine body will brake so make sure you order a new gasket set.
3. Separate the reed valve  from the reed valve spacer and carefully examine the reed valve petals. Be careful not to break them petals. If any of them are missing or cracked you will have to replace the reed valve.
4. Remove the 4 bolts holding the cylinder.
5. Gently separate the cylinder from the main body. Do not twist the cylinder too much when removing it from the main body because it can catch the piston ring and brake it.
6. Remove the 4 bolts behind the main body and gently separate from the crankcase from the back plate.
7. Using a long socket unbolt the crankshaft extension were the spinner bolt goes.
8. Remove the propeller hub and careful not to drop the Woodruff Key.
9.  With a plastic tipped hammer gently hit the crankshaft from the front until it is removed from the engine case.
10.  Check the bearings (front and back) for smooth rotation. If any "scratches" are identified the bearing should be replaced. They come in pairs so may as well replace both in this case. I like to warm up the crankcase in a toaster oven for 15 minutes at 450 degrees Fahrenheit and makes the bearing removal easier. Use wooden or plastic dowels to remove the bearings from the case without damaging the bearing seats.
11. Install the new rear bearing on the crankshaft. To make the operation easier I put the crank shaft in a zip-lock bag and put them in the freezer for a few hours. Now the bearing should slide much easier in the shaft. Insert the spacer sleeve in the crankshaft.
12. Insert the crankshaft from the rear. To make the operation easier I put the crank shaft with the installed bearing in a zip-lock bag and put them in the freezer for a few hours. I also put the front bearing in the same bag too (for the next step). Now the bearing should slide much easier in the body.
13. Insert the front bearing from the front of the crankcase. If the crankcase is warmed-up in the toaster oven for a few minutes it could make the installation even easier. Make sure the bearings are fully seated.

Pictures and more details of the rebuild will follow.