New Engine Preparation


Muffler: The nuts holding the muffler will tend to vibrate loose after a number of flights, regardless of how hard you tighten them. The Saito instructions suggest that for a new engine you should oil the threads, attach the muffler and tighten the nuts; then after running the engine, when engine is hot, re-tighten the nuts. The muffler nuts are still likely to come loose after a number of flights. There are several solutions. The use of Loctite 620 hi-temp retaining compound is said to be an ideal solution, although I have not tried it yet. Permatex high-temperature thread locker is another alternative. Whether you use Loctite or Permatex brand you should get the high-temperature versions of these products. Another solution is to wrap some teflon plumber’s tape on the threads. Another option is to use high-temperature silicone sealant and coat the threads before re-assembling and tighten nuts, however I have found this is not always a permanent fix.

The pressure nipple on the older mufflers can often vibrate, or blow out over time. It helps to fix it in place with JB-Weld. The nipple connection to the muffler is not a mechanically strong joint so you should not stress it by gripping the muffler via the nipple when you tighten the muffler nut.

Crankcase Vent:  Check that the crankcase vent nipple is tightly attached. I once had one that was loose.

IMPORTANT !!   The crankcase vent must be kept open to the atmosphere. This is NOT a pressure tap. It should not be connected to the fuel tank. Its purpose is to allow excess crankcase oil to drip out and it must never be sealed. It is convenient to connect about 4 inches of fuel tubing to this vent so that excess oil drips can exit outside the model; the fuel tubing is also useful because it is easy to squirt after-run oil into the crank-case through this tube. (see also the Maintenance web page).

Saito engine vent rear Saito Engine Vent Front

Note: Most engines have the crankcase vent on the backplate as shown above left. Some have the crankcase vent located underneath the engine toward the front as shown above right.

Carb Needle Settings: On a new engine the low-speed mixture adjustment is set fairly rich. For all the engines except the Saito-30, the top of this adjustment screw is just slightly below the top of the plastic housing as received new (see picture below). For the Saito-30 the low-speed air-bleed screw should be about 4 1/2 turns out as received new. Don’t adjust this as it is a fairly rich setting that is OK for initial starting and running. The high speed needle should be set 4-5 turns out. See the ‘Throttle Setup” page of this web site if you are unsure about the carb adjustment screws.

The above Saito-82a shows the position of the brass low-speed mixture adjustment screw when new; don’t change it because it is preset to make starting easy with a fairly rich setting. For the plastic throttle arm (like on this engine), the top of the brass screw is about 1/2 mm below the top level of the plastic housing. This is a good rich starting point if you need to reset the mixture. If your engine has a metal throttle arm the position of the brass screw should be approximately flush with the top of the throttle arm for an approximate initial rich setting.

Propellor: Make sure the prop that you use is properly balanced with a hole that has been reamed out to the correct metric size. See the “Prop Sizes” web page for more information on prop reamers.

Lubrication:  Before starting the engine for the first time you should thoroughly lubricate the engine. Attach some fuel tubing to the crankcase breather nipple and squirt lots of oil inside, then turn over the prop by hand several times. Remove the valve covers, drip some oil down the pushrod tubes, and on to the rocker arms. See also the “Maintenance” page of this web site.

Muffler Pressure: The fuel tank is pressurized by connecting fuel line from the muffler pressure tap to the tank.

Tank Setup: See the other page on this web site that deals with fuel tanks.

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