Engines

Before running:

I hate to tell you to take apart your nitro motor before ever running it but at this point I do it for every new motor. At least 50% of the time I find little surprises inside and the reason I started to check is that I had catastrophic failures right from the get go.

This is a piston out of a Worlds O.S. Hara engine. You can see there is a piece of steel hanging off of the wrist pin clip. 

Engine Disassembly: 

1) Put piston up to top dead cylinder (TDC) or more importantly away from bottom dead center (BDC) . You must remember to do this otherwise you risk breaking off part of the piston skirt.

2) Remove backplate

3) Remove cooling head

4) Move piston back down to the bottom of its stroke

5) Insert the end of a zip-tie or wooden stir stick into one of the intake ports, not to far

6) Rotate the crankshaft and the piston will push on the zip-tie which will push the sleeve out. Remove Sleeve.

7) Remove Piston very, very carefully

8) Remove crankshaft

Engine Preparation:

Apply the non-drying gasket sealant just like this.

The smallest amount still gets squeezed out. (I put a little loctite on the screws) 

Apply heat transfer compound between the button and the cooling head. This is even more important on an engine like this where the cooling heads lower surface isn't machined smooth. When they leave the cast finish, the heat has to transfer through the tips of the rough surface. 

Apply 3452 Dow Corning grease (or equivalent) to the threads and O-rings of the carburetor. Make sure to notice where they were initially (Flush with the body, 3 turns out from closed, etc).

Apply non drying gasket sealant to the carburetor cinch.

Apply non drying gasket sealant to the carburetor  upper O-ring area.

Engine Break-in 

Items needed:

• Heat Gun
• Temperature Gauge
• Tuning Screwdriver
• Fuel, ignitor, fuel bottle, etc.
• Something to turn flywheel if engine gets stuck at top dead cylinder (TDC)

Overview:

 A controlled wearing-in or seating of the piston and sleeve. The theory of this process is to seat the piston and sleeve at normal operating temperatures with an excessive amount of oil (by using a full throttle extremely rich mixture). Both low and high engine speeds are avoided as well as any sudden changes in engine speed (blipping of the throttle is not recommended during break in)

Temperatures:

Through trial and error we found it best to keep the engine at normal operating temperature during the break-in process, between 200-230ºF. Running an engine cold during break-in doesn't allow the metals to wear or "seat" into each other as easily. The molecules of the aluminum have more freedom to move around each other and mold to the cylinder easier when at a higher temperature. In a cooler running situation if they do happen to reach a point where they wear into each other and you then increase the temperature, say when you start to tune the motor for power, then the components will expand and have to re-seat themselves at this new temperature. The problem now is that you are running a leaner mixture which has less oil to carry away contaminants and reduce friction (in some cases galling can be seen on the piston).

Quick Tuning Guide (After Break-in):

Check for the following symptoms after clearing the engine out (i.e. after driving it around with a couple full throttle pulls or revving the engine a few times on the pit stand)

Top-end or high-speed needle adjusts how high the engine revs, if the engine really screams at WOT than it is probably too lean. If it gurgles, blows a lot of smoke, and is slow than it is too rich. 

Low-end adjusts the fuel mixture at idle and in the low throttle input ranges; when the carb opens past a certain point the needle is no longer in jet and the high-speed needle takes over. If the engine idles without "loading up" than your low-end is lean and the engine will be at higher temperatures than necessary. I prefer the engine to be able to idle for ~15 seconds without loading up but it still needs to load up after some time.

I usually have the fastest engines at the track and the engine temperatures after 5 minutes or 30 minutes are always the same (~210) 

Air Filter Oil:

We run Bel-Ray motorcycle air filter oil, you get a quart of the stuff for $10 and never have to buy it again. I do NOT recommend HPI air filter oil, have had extremely bad luck with the stuff.

After Run Oil:

We run preservative through our engines after we are finished for the day (Always do this unless you run your car every day). The object is to prevent corrosion (aka rust) of the internal parts and to displace any left over fuel.

The chemical aspects of corrosion are very simple in that the surface of metal reacts with something else (metal, water, oxygen, etc.) creating a battery, moving electrons, and converting the metal it into an oxide. The moving of electrons is a basic electrical circuit and so you want to prevent the flow of electricity. A substance that resists flow of electricty is known as a dielectric where the higher the voltage rating, the greater the protection.

Sprayon #711 has a 47,000 volt rating which I found to be one of the highest around plus it is safe on plastics. The engines start right up no matter how long they have been sitting and it doesn't fowl glow plugs.

http://www.kpg-industrial.com/products/711_the_protector_lubricant/

Other commonly used oils are Marvels Mystery Oil and WD40 which are better than nothing.

This is what happens when you let the fuel sit in the engine for months at a time. The fuel turns into a sludge and really doesn't prevent any rusting on its own.

Sludge

The ball bearings and their races were damaged pretty badly