Sweet Engine

I now have an engine that runs so sweetly that I can truthfully say that I've never had a properly running engine before. This is and older (1990) iron piston OS 40FPS that Len modified for me earlier this year. It ran fine in April when I first started flying and through the early part of June, then sat for over a month while I struggled with a virus and pneumonia. The only thing I couldn't understand was why Len said it should take "a little over 4 ounces" to fly the pattern and I was doing it on 3 1/2! Around the middle of July I started flying again and started playing around with props to see if any from local sources would work properly (neither BY&O nor Rev Up are easy to come by in my part of the world). The engine seemed to lack the kick it originally had. I put it down to the hot, humid weather we're currently experiencing. I had taken a couple of vacation days at the end of last week to go with the holiday we get today here in Ontario so I was getting in some flying every day. Friday morning the engine was very difficult to start, wouldn't go over 7800 rpm and died as I turned in the needle valve. After it stopped and cooled off it was very, very tight. I went home, pulled the engine apart and found a lot of black gunge on both the piston and liner (I had been here before with another engine). A little judicious use of some 1200 wet or dry along with some oil aand elbow grease cleaned up things and I put it all back togther.

Saturday afternoon found me at the field again. I went back to where I had started from in April and put on a Zinger 12-5, ground set to 8700 rpm as Len recommends and proceeded to fly with the sweetest engine run I've ever experienced. Fuel consumption was now where Len said it should be so my 4 oz. tank was too small. Saturday night I installed a 5 oz. tank and on Sunday had the four sweetest flights I've ever had. This morning was the same thing in a gusty 20kph wind. The engine just loafs around in a fat 2-stroke and then hauls butt whenever you need it. I used to think you had to fly fast to fly in wind! At the moment I feel it is slightly underpropped, but I can live with that. I do have a Bolly 12.5-5.5 on order and I'm eagerly awaiting its arrival.

Thanks Len for your great work on the engine. Sorry it took me so long to figure it out but sure glad I finally did.

Having been there as well, I can attest to the fact that his plane seemed to go wherever he put it, and didn't show any signs of even being aware of the breeze, even directly overhead. He obviously didn't have to worry at all about slack lines or anything. A real sweet setup, indeed! Maybe by next spring he'll have his Magnum finished to go with this engine.

Nice to hear from you, David, and glad to hear your report on the engine. If the engine ever isn't working right, check the instruction sheet or give send me an e-mail. I am always glad to help out.

David-guess I am missing something here. Were your problem runs due to less than 12" props? or??.
Interesting in that I have been getting some funky runs over the past month or so with a couple of FP's including one of Leonard's. In my case, engines were generally going too lean in air, along about the squares or 8's, this being two different engines, different airplanes. Checked tanks, lines, repeatedly-still no consistency.
Finally talked local hobby shop into stocking some decent CL fuel which is Powermaster 5% nitro, 22% castor/syn blend. Ran it straight out of the bottle and viola! perfect engine runs again. My previous(bad) fuel was Byrons 5%, 18% castor/syn with 8oz of castor added which has provided good results in the past-with this batch(the bad stuff)I outsmarted myself and added a drop or two per gallon of Armorall-this is the only difference and I feel it is the root of the problems I was experiencing. Now I have close to 3 gallons of Byrons/castor/armorall engine cleaning fuel-might could use it for break in's if I stay right by the needle.
Anyway, I am sold on the Powrmaster-22% blend might be a litte light on oil for some FPs. Shop owner has also agreed to stock Powermaster 29% all castor fuel which should be good for the OS 35S, Foxes, etc. or mix the two for desired oil content. It does not take a rocket scientist to figure out that adding 8oz of castor to fuel adds $2.50-$3 per gallon to your cost-insignificant until you figure you are burning 20+ gallons a year.

Forgot to mention that I have scored two 10 prop bags of Rev Up 12-5's on E bay which work well on Len's 35's and 40's as do the 12-6 BY &O's. The vendor, "RalC" out of El Paso seems to run these props pretty regularly and is a reliable seller. Plug in "rev up" on e bay from time to time and see what comes up. I understand the future of Rev Up is very much in doubt so stock up now if you like them.

Jim,

The only prop I tried smaller than 12" was a Bolly Clubman 11.5-5 which was used in an attempt to get back the kick the engine had exhibited in the cooler weather. By that time things were beginning to gum up and any flight results from it are pretty meaningless. My usual fuel is SIG 5% nitro 25% all castor. It's the only all castor fuel our local hobby shop carries and I take my hat off to Karl at Skycraft Hobbies for stocking it for the few C/L types in the area. I had bought some 10% nitro fuel (Canadian brand XL made in Calgary I believe) to try to compenstate for the hot weather. This is 20% oil, 75% synthetic, 25% castor (don't worry, I would have topped it up with extra castor). After cleaning up the engine I decided I wanted to keep a little synthetic lubricant going through the engine for it's detergent properties so I mixed up a bit of approximately 7% nitro (50/50 mix of 5% and 10% topped up with enough castor to bring total oil content back to 25%). First time out the engine loved it and I've used it on the 8 subsequent flights with the same results. I'll keep using it at least until the hot weather passses.

I suspect that the sequence of events went something like this: older engine purchase in 1990 shortly after I returned to flying, subjected to some questionable fuels and some abuse as the result of ignorance on my part causing the beginning of some varnish to form on the piston/liner. Working the engine a lot harder this spring and summer resulted in a lot more varnish forming and the subsequent halt. The first tip off should have been fuel consumption. I was flying the pattern on almost an ounce less than Len said it should take. The fact that I was ruuning that lean to get the ground set engine speed that Len recommends should have made me realize that something was rotten somewhere. Should I run into this set of circumstances again I hope I'll be able to remember this experience.

I've not had any problem with the engine running away. At the moment I think I have the tank just a shade too high - it's not really noticable during inverted flight but seems to really kick in during the ouside parts of some maneuvers, in particular, the outside loops of the cloverleaf. I'm currently using an OS #3 plug which keeps the fires lit nicely in chilly weather yet doesn't preignite in hot (Konstantin put me on to that one}. One less thing to worry about. I'll have few more flights as it is and then try a Graupner 12-5 that I have and see if it's any better or worse.

Thanks for the Rev-Up tip. Since I've never tried one I don't know if I like them or not. Not quite sure I want to shell out for 10 of them to find out. Depends on the price I guess.

Best. Hoovie

Thanks for the clarification-I couldn't figure out why your engine went sour. My Stuka 35FP needs a full 4 oz to make it and may not make it if a little wet. This has not really changed since new.
The two bags of props I got on e bay were extremely reasonable. Lap times are fractionally faster with the rev ups as opposed to BY&0. Line tension overhead may be better with rev ups but difference is minor if any. Hopefully will try the Bolly soon.

I'll let David post the specifics of his fuel here if he wants to, but I can say he mixed up a batch with a bit more nitro and a castor/synth blend instead of straight castor (I use 5% nitro and 25% pure castor, but I'm running "old iron"). He felt the castor content was gumming up the works, as it were.