ircfly

I have a long running saito 65 that ran great one tank and the the next tank starting sounding hot. On landing tha engine was very stiff. After disassembly I found that the engine was dry as a bone. I used solvent in a sonic cleaner to remove all buildup and residue from the engine. I replaced the ring and after reassembly It looks and feels like new. However the problem was not changed in any way. 2 or 3 ounces of fuel and the engine will again be stiff and dry. I do not understand where the oil in the fuel is going. When I oil up the motor and run it I I can see the oil blowing normally out of the crankcase vent. The piston and ring lands are clean. the vent is not clogged. Anybody got any useful ideas?

gkamysz

My Feedback: (19)

What kind of fuel are you using?

w8ye

My Feedback: (16)

All Synthetic oil fuels like regular Cool Power will do this on a lean run.

rcdude7

My Feedback: (264)

That is interesting, I have never seen that happen. I never use cool power either, even my YS engines get a little castor in thier diet.

w8ye

My Feedback: (16)

I think the measure of adequate oil in fuel for four strokes has been to remove the back plate and examine residual oil in the bottom of the crankcase.

With the 16% lube oils and a run with the mixture set correctly, there will be residual oil in the crankcase after a full throttle run. But let a little piece of trash get in your needle and the engine will be very dry inside.

I think a little castor oil in the lube package will give you a little "What If" protection in one of these instances.

I seem to get along well with all synthetic when the total oil is 20% or 22%

But at 18%, I like to see the 75/25 synthetic/caster oil package

I just don't like just 16% total oil in my four stroke fuel. It just doesn't leave enough of a safety margin in case of a lean event. I think 16% total oil (all synthetic) is an invitation to more trouble.

I sometimes buy the 16% oil fuel when I get a good deal, but I add castor oil to it.

ircfly

This was a sudden problem All of my other saitos are perfectly happy with how they are operated. This engine has run for dozens of gallons of fuel perfectly Even on a lean run a saito will overheat then preignite and blow the prop off long before the case goes dry.

charlie1960

I would atleast try a different brand of fuel. At the least, a fresh jug of which ever you run.
Just on the off chance. Ive seen weirder things happen.

blw

My Feedback: (3)

It is easy to try some fuel with at least 2% castor to see how it runs. Richening the low speed needle valve is easy too. If you aren't sure about the expense of fuel with castor, you can buy some at the drug store.

Kimhoff

My Feedback: (22)

With all those leaks t sounds like the crank vent is clogged.

w8ye

My Feedback: (16)

The crankcase vent nipple on some Saito's is almost closed off with a flashing. It takes a scribe to punch out the flashing so the vent will work

SeamusG

A bit of a tangent - I'm having a problem visualizing the source for the castor / synthetic lube in the crank case.

According to my mind's eye (yea, some argue that my eyes are closed) air-n-fuel enters directly into the head through the intake manifold, and sucked through the intake valve into ye 'old combustion chamber. Exhaust-n-fuel residue exits the combustion chamber through the exhaust valve and out the exhaust manifold. There are gaps around the valve guides that allow some unburned / burned fuel residue into the valve covers and then down (upright mounted engine) the push rod tubes into the cam area of the crank case. I guess some air-n-fuel or exhaust-n-fuel gets past the ring into the crank case.

My question (finally) how, by design, does "most" of the oil get into the crank case?

Thanks (and yes, 4-stoke only - no 2-strokes or rotaries)

ircfly

That is exactly the part I am stuck on. The engine is lubed by piston/ ring blowby. I cleaned out all varnish and carbon so that if anything blowby is maximized. The oil does not burn because the is not enough heat in a glow engine so where the hell is it going? I have an assortment of saitos that are all perfectly happy.

wcmorrison

My Feedback: (2)

Oil gets down into the crankcase by "blow by" from around the piston/ring assembly. There is large gap in the ring assembly. About 4 MM from end to end of the ring (e.g. no end of ring overlap). This gap allows a significant amount of lubricant to get by the ring down into the crankcase. The turning of the crankshaft with its connecting rod pin sticking out so to speak, beats the by passed oil into a mist. The mist lubes the sides of the cylinder walls, get on the bearings both front and main, and escapes up the crankshaft to the cam shaft and cam followers and up to the rocker arms. It does not take much lubricant to keep the rockers going (indeed early four strokes had open rocker arms). Consider that Saito and YS for instance say in their manuals use at least 20% lubricant in the fuel. You need it to by pass into the crankcase for lubrication of the moving parts of the engine.

When an excess of oil builds up in the crankcase, the excess is vented overboard via the crankcase vent on the back plate of the engine. Some newer engines from Magnum and OS now have a sort of positive crankcase system where the manifold vacuum is used to pull the excess oil through the cam shaft area and back into the intake manifold. The excess oil is ported through the combustion chamber and out the exhaust pipe. Some of the ported oil may be consumed in the combustion process. But this set up makes for a slightly cleaner engine exterior in that the excess is expelled from the exhaust pipe and not a vent that is sometimes inside the cowling of some airplanes. No matter, I think the positive flow system is better in that it assures lube gets to the cam area.

And like many others, I always make sure there is some Castor oil in the mix. It is a superior lubricant, protects bearings and holds up under lean runs.

Cheers,

Chip

SeamusG

Thanks wc. I didn't pay attention to the ring gap on my Saito 91 when I did its rebuild.

Sidebar - a club member installed a Saito nearly inverterd. He plumbed the lower valve cover with the same fitting used on mufflers for tank pressure and ran a fuel line/copper tube drain tube adjacent to the exhaust to drain the valve cover.

Hobbsy

My Feedback: (102)

This typical of what Jim said about the residual oil, this my 1.00 which I sold a few weeks ago right after a run on green 20/20 that I had left over from my YS days.

gkamysz

My Feedback: (19)

All glow four stroke engines I've had apart have a standard ring gap of .004" per inch of bore. Maybe the Magnums have a bigger gap, but only twice what Japanese engines have. Still oil does get by. It's just one ring and there is a lot of oil on the walls assuming it isn't boiling off.

There is plenty of heat in a glow engine to burn oil. We still don't know which fuel is being used. I know very well that if I run an engine hot on all synthetic right after shut down I can hear oil boiling in some cases and turning the engine over results in a large puff of smoke out the exhaust. This is vaporized oil. Vaporized oil burns just the same as fuel in the engine and vaporized oil is not on the cylinder walls to lubricate the engine.

If you are using a synthetic oil especially something with a relatively low boiling and flash point the oil is boiling and burning.

blw

My Feedback: (3)

The engine can get hot enough to burn oil. This is the main point for using castor for those who do.

ircfly

A glow engine can get hot enough to start burning oil but it should not. (other than in the exhaust) If the oil was burning off in the cylinder I would expect heavy carbon deposits. The amount of time this engine runs before going dry has no relationship to how rich I set it. Blubbering or tweaked to the last rpm 3 or 4 minutes is all there is. I have been tinkering with this motor on and off for the last year or so. That means that the this issue has ranged over many different jugs of fuel. If it was a bad jug of fuel it would have soon been resolved when I used up that jug. Onset was sudden. One flight was fine the next no good. I am baffled by there being clear evidence that there is a normal to a little more than normal blowby with no lube to the bottom end. I can watch the oil I manually put in the case blow out the breather. The piston does not come out dry if anything with the motor set so rich the piston is too greasy. The oil must be exiting the engine in some other way but there is no evidence of any leaks anywhere. The outside of this thing is dry and clean. So the only egress left is out the muffler and I don't see how that is possible. I am very tempted to send this thing to horizon just to get an answer. As a footnote when the engine is running as rich as I can get it the exhaust temp is only 180 deg after 3 minutes at full honk. I cannot imagine any oil burning completely at that temp especially without carbon crapping up the piston and ports.

gkamysz

My Feedback: (19)

The same thing happens on the bench and in the air?

blw

My Feedback: (3)

When it comes to deposits in the engine, you will get more evidence of a lean run with castor than you will with synthetic. Synthetic oils tend to burn up and go out the exhaust.

Mr Cox

I guess the expression "burn up" could be a bit missleading. I think the synthetic evaporates and then goes out the exhaust, rather than actually burn, while the castor will leave a residue even at high temps.

wcmorrison

My Feedback: (2)

Oops, you are right. 4MM is a lot bigger than .004. I did mean to say .004, got the stuff scramble in my head. I was focusing on the the gap and that's the right answer.

On any initial run of my poppet valve four strokes, I take the valve cover off and dribble oil all over the rocker arms and down the push rod tubes before the first run. That way I know the cam area is not dry to start with. The other day, I had the back off YS 63 and before I put a new gasket in, I dribble a bit of compressor oil on the main bearing, back of the crank and on the cylinder walls. I was really surprised how fast it fired up after the work. A little lube goes a long way. And Castor hangs around when the other stuff seems to disappear.

Cheers,

Chip

ircfly

You guys are making sense in that I like the idea that the oil may be vaporizing and just going out the muffler. Out the muffler when there is no sign of a leak anywhere is the only thing that makes any sense at all. I think I will dump a bunch of castor in a bit of fuel and see what happens.