[CJ's Wingman]

Looking for advice on the following engines; Magnum .52 & Saito .56 (4-strokes). Have been using these engines for some time - no problems. Then had both quit in the air - and unable to start after that. Did notice a metallic clinking sound from the Saito before it quit & on trying to restart. Have no experience in dismantling these engines. Does it sound like a valve problem? Am using Byron 15% fuel. Any advice would be greatly appreciated . . .
Blue skies, light winds & happy landings . . .

[OLD PRAIRIE RED NECK]

A bit of clicking on the ground is normal on a four stroke (valve lash noise) but should not be very loud especially if you heard it in the air!

Maybe some bad fuel if 2 engines acted up at the same time.

How about the oil content in the fuel?

Or were they both set lean & fried the glow plugs? Do they have compression?

What have you checked?

[Cougar429]

Some questions might help point to a cause.

How close together did both motors stop running? Was it soon after switching to the new fuel?

Other than the fuel, anything else common to both motors, (ie. were they in the same airframe)? Reason for this is to try and confirm if the cause was external to both motors. If set up correctly and treated right the likelyhood of two failing close together is highly unusual.

Does anything feel or sound out of the ordinary if you rotate the motors by hand? This would mean roughness or inconsistency from something mechanical such as gears or bearings.

Not familiar with the Magnum, but I would suspect this recommendation would work for both motors. One thing you can do is to remove the rocker cover(s) and if nothing looks out of the ordinary, such as a broken valve spring, then rotate the motor and view the action of the valvetrain. There should be minimal clearance between the rockers and valve stems when on compression and none at all away from that point.

Where in SW Ontario are you located?

[kip51035]

The large change in the weather lately makes the need on some engines to retune both the high and low speed needles, also a hotter glow plug might be in order. Leave the glow heat on and warm it up first. If it looses RPM when you take the heat off you need hotter fuel or plug.

[Max]

Had 2 Saitos break a valve spring over the years.

Cause: Overheating. Overheating caused the valve spring to anneal and lose its spring strength. One actually broke

Root cause: Bad fuel, which caused me to run leaner and thus hotter for the same power