blw

My Feedback: (3)

PCV and normal venting

First, some back ground. The Japanese have much tighter emission controls on engines, and they are influencing some Japanese manufacturers of model engines. In this country the Eco-Nazis are trying to get all piston engines covered by federal regulations. In California where most of the nuts are already out of the wood work, the C.A.R.B. has mandated emission standards on lawn equipment - that's why you buy weed eaters there with four stroke engines now.

The case vent going back to the intake is very close to the Positive Crankcase Ventilation on our cars, differing in that auto engine have valving to ensure a constant flow through the case into the intake over and above the amount of piston ring leakage. The model 4s engine vented this way would have only the ring loss to flow back into the engine's intake.

It does have the advantage of catching the oil that would otherwise go onto the plane or the ground, but if you're running a castor blend (as you should be) I really think there's about as much going out the exhaust as out the vent.

The disadvantage is the volume of air from the case will displace an equal or greater (because of temperature expansion) amount of fresh air being taken in, leaving less free oxygen, and not being able to burn as much fuel. This leads of course, to lower power available.

I think it is worth an experiment. Set your Saito up with the recirculation and see how much difference it makes. At the same time, to be fair, plug the recirculation on your OS and see how much power it gains. In both cases you'll have to reset the mixture.


Prop drive

The prop drive is on a centering cone with an angle that is referred to as a "Locking" taper. It requires a strong puller that will latch into the groove in the drive washer. Some have had success with inexpensive pullers, but many just ruin the cheap ones. Many auto supply stores will lend tools, you might visit one and pop the drive off while you're there.

The puller I use is a lot more money than you would want to have sitting unused for 99.999% of the time, but I do use mine often. It's a Snap-On tool.


Tappet changes and “S” big block models

Not mushroomed cams, but the tappets. The increased diameter of the cam end of the tappet will increase the valve duration and overlap with no other change. In the first attached picture the plain tappets are in the left column, what I call "Mushroomed" tappets are on the right.

This composite shows all the external differences between the old style big block engines and the "High Cam" versions. Also shown is the original "S" cam, just used for a short time in the original FA-120S. If you see a 120 with a curved intake pipe instead of the cast pipe it's an "S" model, the hot one. The later "S" 120s had the cast pipe and a normal cam, but still with the wide headed tappets so they were still a bit hotter than the early ones.

Second picture is the hot "S" 120. See the intake? Third picture is the standard 120 cylinder next to the "S", both shown with the intake pipe. Finally, current production FA-120S showing the return to the cast intake.


Cam bearings and oiling, gear lash

All Saitos have cam bearings, but if you mean ball and/or roller bearings, no. The camshaft has bronze bushings that run on a 4 mm steel shaft.

An alternate way to oil the cam, its bearings, and the tappets is to put a big slug of oil in the crankcase, then hold the engine nose down to get the oil to run up front, then angle the engine back a bit to get it all into the cam chest.

Other ways to get strange noises in a Saito:

A seized crank bearing sliding the balls instead of rolling them, this is rare, almost unheard of. The other is an assembly problem, not leaving enough clearance in the timing gears. This is set by selective thickness of the cam box gasket. If you always use the gasket from the engine kit you're OK. If you have too much clearance the typical "Click" as you turn the engine will be louder - it's the intake tappet pushing the cam forward against the gear teeth.