Four stroke engine maintenance

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How do the valves get lubricated in my thunder tiger F54S? Should I grease them?

 

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It looks very dry in here...

 

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[NitroR/C]

I don't think grease is necessary, just use oil.

 

[fstnd]

It felt so great disassembling such a different engine for the first time, that I forgot about a little thing... valve timing lol. I'll have to figure out, and I'll make a test bench because I probably won't do it right the first time

I don't think grease is necessary, just use oil.

I just realised that all oil will instantly be sucked into the compression chamber. I'll oil it of course anyway but it'll take a while to unflood the engine. I don't understand how these valves get lubricated...

 

[tudordewolf]

It felt so great disassembling such a different engine for the first time, that I forgot about a little thing... valve timing lol. I'll have to figure out, and I'll make a test bench because I probably won't do it right the first time

I just realised that all oil will instantly be sucked into the compression chamber. I'll oil it of course anyway but it'll take a while to unflood the engine. I don't understand how these valves get lubricated...

Enough oil sneaks through the valve guides, I think it gets blown up through the exhaust valve and drawn back down through the intake. if you don't gasket the rocker cover it'll leak oil, if you invert it it can fill up and even run that way, though I believe it "empties" during full throttle.

here's the .52 on mine, a little hard to tell but they're oily.

 

[fstnd]

I set up everything, but as expected, the valve timing is incorrect. I see fuel being pushed back into the tank. Is there a quicker way to change valve timing than to reposition the crankshaft?

 

[NitroR/C]

I did a search with the help of AI and got this. I hope it helps.

Valve Timing and Adjustment Procedure for Thunder Tiger F-54S
Correct valve adjustment and engine timing for the Thunder Tiger F-54S are fundamental operations to ensure optimal performance and prevent mechanical damage. This 8.86 cc four-stroke engine, featuring a 24.0 mm bore and a 19.6 mm stroke, requires a methodical approach to maintain synchronization between the camshaft and crankshaft, as well as the correct clearance between valves and tappets.
Tool Preparation and Safety
Before starting any work, it's essential to have the appropriate tools: a set of hex wrenches, calibrated feeler gauges (0.05-0.15 mm), a dial indicator or TDC indicator, and a protractor for checking valve opening/closing angles. The engine must be cold and mounted on a stabilized test bench, with the propeller removed to prevent accidents. During operations, maintain a safe distance and use protective gloves to avoid cuts from sharp components.
Cylinder Head Removal
Removing the cylinder head (part number PN0149) requires unscrewing the four top bolts with a 3 mm hex wrench. Before disassembly, mark the camshaft's position relative to the crankshaft using a permanent marker to facilitate realignment during reassembly. During this phase, inspect the valve seats for any signs of wear or carbon buildup, cleaning them with a cloth soaked in a specific solvent.
Valve Clearance Adjustment
Identifying Top Dead Center (TDC)
Position the piston at compression TDC by rotating the crankshaft counter-clockwise until the "TDC" mark on the flywheel aligns with the reference notch on the crankcase. Verify that both valves are closed: in this position, the valve rockers should have measurable play between the cam and the tappet.
Measuring and Adjusting Clearance
Insert the feeler gauge between the valve head and the rocker arm, checking that the value matches the manufacturer's specifications (0.08 mm for the intake valve and 0.10 mm for the exhaust valve). If the clearance is insufficient or excessive, loosen the lock nut on the rocker arm adjuster with a 5 mm wrench and turn the adjusting screw with a flat-head screwdriver. After adjustment, re-tighten the nut while holding the screw to prevent slipping.
Timing Procedure
Camshaft Alignment
Correct timing requires precise positioning of the camshaft relative to the crankshaft. After removing the cam cover, verify that the reference mark on the camshaft's gear is oriented towards the top screw of the cover (Fig. 3 in the manual). This alignment ensures that the valves open at the correct times in the thermodynamic cycle.
Checking Opening/Closing Angles
Using a protractor mounted on the crankshaft, determine the valve opening and closing angles:
* Intake valve: Should open 15° before exhaust TDC and close 45° after intake BDC.
* Exhaust valve: Opens 45° before expansion BDC and closes 10° after exhaust TDC.
Any discrepancies require removing and repositioning the camshaft, ensuring that the gear teeth do not show any play or wear.
Post-Adjustment Checks
Compression Leak Test
After reassembly, perform a compression test by connecting a pressure gauge to the glow plug hole. Optimal compression should be between 8-10 bar when the engine is cold. Values below 6 bar indicate valve leaks, necessitating seat grinding or valve replacement.
Bench Test
Start the engine with a 20% oil (preferably synthetic) and 10% nitro fuel mixture, using an 11x6 propeller to avoid overloading during break-in. Monitor idle response: a stable idle speed around 1,800 rpm confirms correct adjustment. Any oscillations or sudden shutdowns require re-checking valve clearance and timing.
Preventive Maintenance
Periodic Inspection
Every 10 hours of operation, check valve clearance and seat cleanliness. Carbon buildup exceeding 0.5 mm in thickness should be removed with a non-abrasive tool to prevent compression loss. Lubricate the rocker arms with specific four-stroke engine oil during each service.
Replacing Worn Components
The valves (part numbers AA0474 and AA0475) and springs (PN0146) should be replaced every 50-70 hours of use, especially if there are signs of deformation or reduced elasticity. During replacement, re-verify the timing to compensate for any tolerances of the new components.
Conclusion
Valve adjustment and timing for the Thunder Tiger F-54S require precision and attention to detail, with particular emphasis on mechanical alignment and adherence to manufacturing tolerances. The use of calibrated tools and adherence to the procedures described in the technical manual ensure reliable operation and consistent performance over time. Regular maintenance, combined with systematic verification of operational parameters, constitutes the optimal strategy for preserving the structural integrity and thermodynamic efficiency of this engine.

 

[fstnd]

Thanks, I've reset my engine valves. The fuel is still being slightly pushed back into the fuel tank when I block the carb with my finger but... whatever. The engine sounds to me like it did before I touched it. Video:

 

[NitroR/C]

I have never had a 4T engine but it seems to run well by ear.

PS: perplexity.ai is really great for doing research.