Cougar429

My Feedback: (3)

Bill, welcome to the Saito club. You'll be hooked for life now.

That screw can be set to allow the throttle barrel to JUST close even before mounting. It should not be used to set the idle speed since it would then prevent stopping the engine with the radio. I normally set mine so the throttle trim on the Tx controls the idle speed and the spring loaded "Trainer" switch is programmed to close the throttle completely when I want it to stop.

When you first stated it would not run, wanted to ask if you confirmed good compression. Asking as there are a few things that can stump getting one of these firing off that can be exacerbated from long storage:

First is a stuck or leaking valve. If it sat with one or both of the valves open for a long time then carbon on the exhaust, gummed up lube or simply a bit of carbon stuck between the valve and seat can cause a compression robbing leak. You can tell where this is coming from by simply listening at the intake or exhaust ports while winding the motor around to compression stroke. A hissing or whistling will tell you that compression is forcing air out somewhere.

NOTE: You will near that whistling anyway from the case vent as a normal process from the piston moving up and down, so will have to try and focus on the ports instead.

Second and more insidious would be a result of a hard stoppage and I have ONLY seen this on a 65. A friend had me tear his down since after a boink he could not get it started. I found it had torn some cam teeth loose so the crank was turning, but the cam was not. Does rotating the crank have the rockers activate?

A final cause of low compression would be a stuck ring. I once added a metal conditioner to my standard After Run Oil mix as it had a pretty tenacious "Stickiness" I thought would make it bond to surfaces better for storage and protection. Worked that way quite well, unfortunately it also seemed to harden pretty good after a while. With engines stored successfully for 20 years or more with my stock 50/50 mix of ARO and Air Tool Oil, to see this occur with the second 125 in approx a year was disappointing and required a teardown to free the ring.

Last and most simple is a failed glow plug. Have you tried the plug out of the head to see if it works?

Also the final question, how do you have it mounted? Orientation and tank height can perhaps be the problem and simple changes all that are required to solve it.

Only warning I give to new 4-stroke owners is to NEVER have yourself or others in front of the engine or to the sides, especially when first setting them up. Saitos do not like to run lean and can stop on a dime once you wind them up to work on the HS needle. This frequently ejects the prop at high speed and energies.