Engine Mount

Engine Mount: Any type of mount is fine. The Saito-180 seems to have significantly more vibration than the 120 and 150 and a soft mount for the Saito-180 might be a good idea depending on your particular airframe and tolerance for vibration. If you choose a soft mount the “Soft n Safe” mount sold by Gator RC Products is a good one as it is not too soft but provides some reduction in vibration.

Upright, Inverted, or Side Mount ??  Any engine orientation is OK. A frequent question is -- can I run the engine inverted ?  A scale or pattern type model looks better with the engine inverted. Inverted engines run fine but can be a real inconvenience when starting. Attaching a glow-plug ingniter, and keeping it on, can be a real pain. Also fuel may accumulate inside the piston when inverted, causing hard starting, or possibly engine damage when forced over with an electric starter. This latter problem with inverted engines is minimized if you turn the engine over by hand 5 or 6 rotations before attaching the glow plug battery; any excess fuel inside the piston will run out the exhaust (if the exhaust points downward). If you are new to 4-stroke engines it is preferable to mount the engine vertical or sideways. It is important to note that the centerline of the fuel tank should be level with the carb or a little lower; if you invert the engine the tank  may be a long way above the carb and you may have fuel running down into the carb making it difficult to get the fuel mixtures correct. Therefore, before deciding on an engine mounting orientation remember to consider the tank location. If the idle mixture is set correctly there should normally be no need for an on board glow system.
The dreaded “hydro-locking”. Often mention is the term “hydro-locking” with inverted engines. It is easy with an inverted engine to get the piston full of fuel and it will be difficult (or maybe impossible) to turn over the engine by hand and application of a strong electric starter may damage the engine. The instructions with engines purchased from the  Horizon Hobbies (distributor in North America) suggest that in such a situation you should remove the glow-plug and drain the excess fuel. While this will work, I suggest that procedure is inconvenient, unnecessary, and undesirable. It does nothing except wear out the glow-plug thread, maybe strip the thread in moments of frustration, and certainly waste a lot of time. There is a simple fix; (with glow-plug igniter removed) just pick up the model and tilt it sideways so that the exhaust port points down, turn over the prop by hand and you will see the excess fuel that was in the cylinder run out the exhaust.
For an inverted engine you should first make sure you can easily turn over the engine by hand before applying an electric starter.

Saito inverted mount

Inverted Saito-150 in 2m pattern model. Note fuel tank over wing. Model uses a Perry pressure pump.


The metal mounts sold by JTEC are already drilled and tapped and are therefore quite convenient. However these mounts are somewhat heavier than plastic mounts. Saito also sell similar metal mounts. They are also nice, easy to use, and come with mounting hardware. However they are also much heavier than plastic mounts. The Saito mount for the Saito-220 weighs 10.7 oz (part number SAI220A95)  Since the Saito-220 is such a large engine you might be better off with a metal mount, despite the extra weight compared to plastic.

Kyosho Sensation: Weight 5 pounds 14 oz       Saito-91 mounted inverted, APC 14x7 prop, Dave Brown 60FS engine mount, Perry P-30 pump, standard tank that came with model mounted over wing, 5 cell 800 mAH battery under the rudder/elevator servos. Picture at right shows pump mounted just behind engine.

Saito 45 degree mount

Saito-91 mounted downward at 45 degrees from horizontal. This is a convenient way to mount the engine as the muffler exits at the bottom and is mostly hidden from view. This particular setup uses a Perry oscillating pump and tank just behind the firewall. The oscillating pump is mounted on the engine firewall.

Here are some examples of Dave Brown plastic mounts.
for Saito-30      -- Dave Brown mount 202L
for Saito-50,56 --  Dave Brown mount 4045L
for Saito-72,82a -- Dave Brown 60FS-6004
for Saito-91     --   Dave Brown mount 60FS                           or      Dave Brown mount 90FS  
(Use the 60FS for tight cowls. The 90FS has longer beams and a bit larger back-mount size.)
for Saito-120,150,180 -- Dave Brown  120F

Saito inverted in Kyosho Sensation

The rear-mounted throttle arm on most 4-stroke engines can make the servo linkage quite difficult. The DuBro “4-Stroke Throttle Linkage” can make the servo connection more convenient. A typical setup is shown to the left.

Compatible Engine Mount Sizes
Saito-45S,50,56,56F,62,72,82a (all these have same mounting dimensions)
Saito-220, FG-36

The Saito Metal Mounts
If you are not concerned about the extra weight of a metal mount compared to a plastic mount you should consider the Saito metal mounts. For the larger engines like the Saito-150,180,220 the plastic mounts are probably not advisable. The part numbers for the Saito metal mounts are as follows.
Saito-220 and FG-36:   SAI220A95
Saito-120,150,180      SAI120S95
Saito-100 and 125a     SAI10095
Saito-65,80,91,115      SAI6595
Saito-45,50,56,72,82   SAI5095
Saito-40a                     SAI40A95
Saito-30                       SAI30S95

The dimensions of the Saito metal engine mounts are shown below


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