Okay... I'm totally confused now.
My buddy just picked up a YS 1.10 for his new bird, which prompted me to pull my Magnum .91 out and dust off an old P47 ARF that I've had for a couple of years.
I always thought that all YS engines used YS20/20, other 2-strokes would use standard Powermaster 5-15%, and other 4-strokes would use Powermaster 4-cycle fuel.
Not seeing Powermaster 4-cycle anymore, and one of the shop guys said to just run the 15% that I've been running in my 2-strokes.

Now my buddy is telling me that he's read (on RCU) that castor will gum up the valves, and ALL 4 cycle engines are best run with 20/20.

Tower's write-up on the Magnum says:
2-Stroke Fuel (Recommended: Power Master 10%, Not Carried)
Break-In: No More than 15% Nitro-Methane, No Less 20% Castor Oil.
After Break-In: No Less Than 16% Castor Oil Should Be Used.
Synthetic Oil Content Should Not Be Used.

The instructions that came with the engine say:
The Magnum XL 80 & 91 Ringed Four Stroke Cycle Engines run on standard
commercially available model glow plug engine fuel. Because these
engines are Ringed, it is especially important to fuel with castor oil, with
a recommended 18%. Additionally, a fuel containing 5-15%
nitro-methane is recommended.

Who's right? Has the experience of the RCU members discovered something over time not indicated in the manual and on Tower's site, or is my buddy listening to the wrong person?

IMO all four strokes perform better with 14 to 18% oil, but warrienties may be voided, thought I don't know how they would know. Four strokes do not need as much oil because the oil remains in the crankcase till it fills up and the excess is dumped out the breather. Some may have lube problems on the rockers with low oil content, thought mine never did. A small amount of castor improves lubrication and doesn't affect the valves. Saito used to require all synthetic oil, I think they now recommend a small amount of castor in the mix.

YS is a bit differant as all of the oil goes throough the crankcase and should have at least 18% oil, 20% is better. I think castor is bad for their diaphram. Sure some YS owners will give you the right info.

For all YS 4-stroke motors, perhaps the best fuel is 30% Heli for power and ease of running. 25%, and 20% Coopower also work very well. I have also used the 20% Pro-Pattern Coolpower which works well but is actually more expensive than the 25% Coolpower. I understand that the Japanese use a sythetic blend with only 15% in their YS 4-stroke.

My experience is that 30% Heli is the absolute best but it is not absolutely necessary.

I only use Coolpwer as the other American premium brands are not imported to Europe. I would bet the Wildcat and the other premium blends would work as well as Coolpower. Plugging for Coolpower, Morgan Fuels is a huge supplier to competition sports requiring exotic fuels and they surely know their business.

Again, any of the Coolpower (all Synthetic) fuels with 20%-30% will run nicely in the YS motors. They also leave the motor free of varnish and deposits.

Mark

Horizion advocates 30% Heli fuel for the oil content and the fact that the extra nitro improves idle and accelaration in the Saitos.
All other 4 stroke manufactures advocate regular 2 stroke glow fuel. That's what they where all designed to use. 15% Nitro helps idle and accelaration.
A small amount of caster in the fuel is good, say 5% to help with film strength. But to much and it can build up on the exhaust valve if you run the engine a little to hot.
If you read the book by Clearance Lee of RCModeler titled the RC 4-Stroke Engine, it can help with a lot of questions. [&:]

Good tip. I have a lot of respect for Mr. Lee.
So it sounds like my regular Powermaster 15% will be fine for this Magnum. Guess my buddy just bought two more gallons of 20/20 that he doesn't know about yet

Just another note,

It has been said that some castor in 4-stroke fuel will act as a rust inhibitor and eliminate the need for after run oil. I have been running 2 stroke fuel with 18%-20% oil and some of it being castor for a number of years. Well, no gummed valves and no rust to boot. I do use after run oil though....hehe.

Tom

Since all YS engines have a NIKASIL like sleeve, the Castor oil protection so revered in ABC/AAC/ABN engines is not necessary.
Also, it (the Castor oil) is said to gum up the fuel pump diaphragms and valves.

Use 20/20 YS, or 30% nitro heli fuel for best performance, in YS engines.
Use the full 20% synthetic oil, in all YS engines.

For any other four-stroke, 10%, sometimes even 5% nitro is good, with a synthetic/Castor oil mix.
For an improved idle, response and power, up to 20-25% nitro can be used.

Castor in the fuel (Except in YS engines) is correct for these reasons:

Anyone telling you to run all synthetic has their head in the sand. Anyone telling you that some castor in the fuel will gum up an engine has their head further in the sand. These folks claiming this don't know that:

1) good quality castor oils like Klotz brand, (which is the same brand that Wildcat fuel uses for their Premium and Premium Xtra fuels, and any of their castor content fuels) are very good quality and "degummed" which means they are clean burning and offer superior protection. Yes, they will turn your piston a caramel color, but that is fine, means the oil is working properly, and it is not gumming up your engine. Castor oils from 40 yrs ago, were not "degummed" and would run much less clean. And they were ALL castor content fuel lubricant package. Not 20 or 30 percent of the total lube amount. I think the anti castor guys don't want to accept this or realize this. Old and outdated word of mouth dies hard.

2) Castor oil is a superior lubricant, especially to protect against hot and/or lean runs. Part of the job of oil in the fuel, in addition to lubrication, is to carry away heat, or "heat disippation". Castor does this better than any synthetics can. The engine gurus know this, recommend this, and will tell you this if you read their engine reports/columns, i.e., Dave Gierke and Clarance Lee.

3) Because synthetic is a different chemical composition than castor, increasing the content of synthetic from 17% to say 22%, (or whatever) will not give similar protection as castor. Because they are different oils, no amount of extra synthetic added can make up or duplicate the qualities of castor. This is because they are different.

Am I against synthetic? No. I suggest and believe in fuels with BOTH castor and synthetic lubricants. Ideally 30 castor and 70 synthetic. (or 20/80 if you like) This is because each one has certain qualities, strengths, and weaknesses. Used together like in Omega, Wildcat Premium, and Premium Xtra, you will have superior engine and bearing protection than all synthetic.

If you really want to be kind to your engine, run a total lube amout of 20%, divided 20 or 30 and 70/80.

As far as all synthetic proponents, they are the same guys telling you to forget the low rpm breakin on a 4 stroke with a test stand, and usually tell you to breakin the engine flying the plane.

And don't forget this: All synthetic only guys seem to justify the use of all synthetic lube by saying that the engine runs just great. Well sure it does, but that doesn't mean anything. The point is that it will WEAR LESS and LAST LONGER by using a fuel with castor content. And if that's the goal, castor is the ticket. Period.


http://www.rcuniverse.com/forum/m_13...tm.htm#1329330

That's kinda what I was thinking. It matched what I had always thought, but wasn't 100% sure.
I remember about 8 years ago, my buddy (different one, not the one telling me to run synth) bought a gallon of Hobby Shack's house-brand fuel and it left an awful black gunk all over the side of the plane AND would not tune worth a darn. When he complained about it, the guy at the shop told him that it was 100% castor and would do that.
We just dumped it and went to Powermaster, never turning back.

Anyhoo... ya, my buddy recommending synth is totally unfamiliar with 4-strokes, and was repeating what he had read here, however, his frame of reference is his new YS 1.10. Where the comment came from that it would gunk up the valves, I have no clue, but I know him well enough to know that he wouldn't make stuff up. 'N fact, if there were any way to save the $5/gallon, he'd run straight 15% Powermaster in his YS

Read This for good info from the maker of both types of fuel. It is very informative.

http://www.powermasterfuels.com/facts2.htm


Max

I disagree that 4 cycles need less oil The entire engine is lubricated by oil that is blown by the piston ring. Not much oil as far as I am concerned and what little oil is blownby the ring is blown out the vent by blowby crankcase pressure. I'd use nothing less than 18% oil for a 4 stroke. Just because it runs better on lower oil doesn't mean its better.

Ever tilt the plane on its nose and have oil pouring out the vent? Or opened up the backplate after taking care not to let it over flow into the vent or up the cylinder? Well I have and I assure you the crank case fills up with oil right up to the crancase breather. The fact that the breather is now on top is one reason four strokes have problems running inverted. Too much oil in the crankcase slowing down the rotating inertia keeping the engine turning between power strokes. Some engines have a groove between the back plate and case to allow excess oil to flow into and prevent excess drag on the rotating crank and conrod. If they get enough lube to the top end, they run fine on 14% oil, maybe less.

[quote][Anyone telling you to run all synthetic has their head in the sand. Anyone telling you that some castor in the fuel will gum up an engine has their head further in the sand. These folks claiming this don't know that:/quote

Why are all my engines that run on Caster gummed-up while the ones run solely on 100% synthetic remain spotless inside and out?
If Caster is so much better than synthetic, why are all the heli, car and DF fuels 100% synthetic? Because they run hotter, harder and faster than most plane engines.

Someone had a thread a while back about 'Bearing Failures' -- I posted pics of two engines there.
Take the back cover off of one your engines run on de-gummed Caster and one run on 100% synthetic and tell me what you see.

Kirk

Nope, never had a crank completely full of oil in a 4 stroke Maybe your aren't breaking in your 4 strokes correctly and getting excessive blowby past a ring that isn't seated properly???

I didn't say the crankcase is completly full. Just full up to the crank vent or about even to the bottom of the crank. Inverted engines drain much of it past the rings into the cylinder. Though rare it is possible to hydro lock them from oil that has drained past the rings into the cylinder after shut down.

Don't know why you are replying to me and quoting someone else. Don't know about car fuel but most heli and ducted fan fuel has castor oil. In fact some ducted fan fuel is 11% castor and 11% synthetic. Castor varnish is good for your engine. It has to be very old or run with 100% castor oil to gum up significantly.

Yup... I was curious about this, so checked when I was at the LHS today. The only 100% synthetic fuel they carry is YS20/20. Everything else, including their 30% and higher nitro fuels marketed at the nitro car guys, is a synth/castor blend.