11 Practical Tips for Assembling a FL4-175 Engine Model | StirlingkitSeptember 23, 2022
Every engine hobby builder has its own theories and methods that have worked successfully for multiple builds and rebuild. Here are a few tips and tricks that might come in handy while you plan to build an FL4-175 engine.
1. Installing cylinder liners and O-rings
A wooden dowel can help install the cylinder liner O-rings. Make sure the o-rings are seated in their grooves in the engine block, to avoid pinching the o-ring while installing the cylinder liners. Take your time with this step ensuring the o-rings are correctly seated. For the each cylinder liner installation, make sure to clean and oil each cylinder liner before installation. If an o-ring is pinched between the engine block and liner, coolant can leak into the crankcase.
2. Oil adjustment grub screws
When installing the grub screws that adjust oil volume to each outlet, install the oil fittings and use a small squeeze bottle filled with oil to force oil through the oiling orifice to see the oil flow to each outlet. Once the grub screws are adjusted for even oil flow, use high temp gray silicone sealant over each grub screw to prevent leaks.
3. Brass Cam gear installation
When installing the inert brass gear, cam drive gear and crankshaft gear, the fit will initially be snug. Use a little assembly lube on these gears, and once gears are installed, rotate the crankshaft to work-in the grease. The gears will fit correctly and rotate smooth once the engine has been started and run-in.
4. Pistons and piston ring installation
We recommend using the 2 cast iron rings option when building the FL4-175. Install the upper and lower piston ring with the ring’s end gap staggered 180 degrees apart. This prevents blow-by. When installing each piston connecting rod, note each number that corresponds with each cylinder position.
5. Piston & rod installation
Install piston & rod assembly through the top of the cylinder liners. Oil each piston assembly before installation. Use your fingernail to compress each piston ring, until the piston & rod assembly drop into the cylinder liner. Do not force the piston; ring / sleeve damage can occur. When installing the connecting rod end caps, line up the reference marks on the cap and rod end. Use blue loctite on the connecting rod end cap screws.
6. Starter gear & bearing
When installing the bearing in the large starter gear, make sure the bearing ID numbers are on the side of the gear with the smaller center boss. Place the 2.5mm starter motor screws in the holes before installing the large starter gear onto the shaft. Using a dab of RTV sealant can help hold the small pin in place on the crankshaft. Lightly grease the gears on the starter motor gear assembly. The new Cison geared starter operates well on a 2 cell 7.4 volt battery. Do not use an 11.1v battery, motor damage can occur.
7. Valve, spring, and retainer installation
When installing the screws in the valve tappets, it is very important to use blue loctite to prevent the screws from backing out of the tappets. After installing the screws, let the loctite dry, then wipe any residual loctite off the tappets before installing them in the block. The valves are each numbered and have a matched location in the engine block. Using tweezers and a pick can help install the springs, retainer & clip when installing the valves.
8. Oil pump assembly
The driven oil pump gear no longer uses a dowel pin. The absence of the dowel pin will not cause problems with the oil pump.
9. Water pump assembly
Use loctite around the water pump front seal to hold the seal in place. A thin layer of RTV sealant on the water pump gasket / shim can prevent leaks.
10. Pulley installation
The pulleys are held in place using loctite. Make sure the pulleys line up with the 2 belts. Loctite can be removed using heat from a pen-torch.
11. Trigger magnet installation
A vise can help installation of the trigger magnet in the pulley. It is important to face the colored side of the magnet outward, facing the Hall Effect sensor.
Edited by Jon Cook
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