When i first got my OS40 LA, i was suffering from major impatients. Inever broke the engine in as per the manual. It seems to run fine now that i have run about a gallon though it.... should I go back and rebreak it in, is that possable or should it be fine to keep running as is.

If it aint broke, don't fix it.

Leave it alone now. Next time...make sure to follow the manual. You might not get so lucky on the next one.

+1

Ialways used thefuel and fly break in with the LA series afterI used a touch of lock tight to the four head screws. They don't require a lot of breaking in.

The .40 LA is one tough little customer.  Most pilots just fill them up, tune them ever so slightly rich, and fly them with no more than a tank or so on the ground.</p>

It's not likely you did any harm to your .40 LA, enjoy!</p>

engines these days really dont care. sometimes they wont idle well/wont be as powerful but </p>

as long as your are not lean (the most important one), dont run the engine at full throttle or idle for more than a few seconds (for the first half gallon or the first couple of tanks depending on the engine), you should be good to go.</p>

</p>

In over 30 years of flying, I have never broken in a 2 cycle any where other than in the air. I run them on the rich side for a dozen flights or so and then lean them out a bit. Now 4 cycle is a different story. They need to be broken in as they are a lot more picky about things. If you see a dark grey almost black oil residue on your plane, then you might have an issue with the engine, however it usually turns out to be a loose screw on the muffler or engine mount. Good Luck, Dave

The OS LA series are a very user-friendly engine. Keep in mind they are a plain bearing engine rather than a ball bearing example. You not only need to break in the piston/cylinder liner but the crankshaft/bushing as well as the conrod lower and upper ends.

Best way to do that is run it per manufacturer's instructions. Most important factor is to use a proper fuel. I wouldn't recommend an all-synthetic blend for the first gallon. At least some castor and a minimum oil content of 18-20%. Go to a smallish prop and run it to just barely below peak RPM. A couple of tankfuls like this on the ground will give you an engine capable of maximum performance and longevity.

This from the OS Max Engine Manual for the LA 40, 46 and 65 engines:

Running in &amp; ordinary use: 20% castor oil, 5% nitromethane
More power &amp;flexibility: 20% castor oil, 15% nitromethane

Only readily available commercial fuel with 20% castor is Sig Champion all castor. I'm sure their regular Champion fuel would work OK. It has a 50/50 castor/synthetic blend but same overall oil content.

I bought a quart of castor oil at the LHS and add abit to the gallon for my bushinged engines, especially during break-in. Powermaster fuel has a 15%nitro,18% oil, 1/3 Castor and 2/3 synthetic that I currently use.

jack

Pretty much how Ido it too unless the two stroke has a ring. The SK engines Itake the time to bench run and they break in a bit different then other two stroke engines. Takes a bit of time but they really are great engines for any price.

If you already ran a gallon through it, I'd say it's already broken in!

40 LAs are nice little engines, but they're a little wimpy for most 40 sized planes. The 40LA is right between the 25FX and the 32SX for power and weight, so I actually use mine on 25 size planes. I consider it a "poor man's 32SX". It'll do OK on a 40 sized trainer, in fact I'm planning to put one on a 40 sized Tower Trainer for my son. He likes to peg the throttle and yank the controls around, so the slower flying the plane, the better!

Wimpy is in the eyes of the beholder.</p>

I  fly a TT GP42, which is essentially the same as the LA40 and properly prop'd it pulls a 6.5 pound spad Trainer (Debonaire) around very nicely.  Good loops, quick take off, etc.  While it may be a stepping stone, it's not a wimp.</p>

Jack</p>

As I said, it will fly a trainer OK, but it's pretty wimpy for most 40 sized aerobatic or 3D planes.

The .40 is a bit on the short side of power, I used one on a trainer and it worked OK. On the other side of that is the .46 LA and Iused and still have a couple of them. Iused nothing but the .46 LAs on the Tower Up-Roars and any of the other fun fly planes Iwas building. They weren't all that far behind the .46 FX in the fun fly planes but fell off a bit in top speed.

I use Rich's Brew fuel with 5% nitro and 20% all castor oil.

Iwonder what all those people that mix their own fuel, and successfully fly with it, AND have longevidy with their engines, would say about that.

Brand name fuel is just that.. brand name fuel.I happen to use S&amp;W from Pennsylvania.It's just fine and it's what the LHS has in stock. I've also used CoolPower which is what the other LHS has in stock.It's just fine. I've used the Tower brand, expensive to ship, but available.It's also just fine. If it's quality fuel, it doesn't matter who makes it.. even if it's made in the garage.

As far as breaking in your engine is concerned, if it runs ok, well,I guess you lucked out. Iusually run a tank or two, very rich, (Iwon't go through the break in procedure because that's in the manual), and then fly it. It runs better after each tank of fuel for the first 10 tanks or so. I only fly OSengines, by the way, from .46 to 1.60 with just about everything in between.. and they all run just fine. Can you break it in while flying it? Well,Dave says he does, and has never had a problem. I guess it comes down to personal choice. Since I was taught to break them in, I follow a modified procedure, but as I said, I do run a tank or two through it on the ground before flying it. I guess it comes down to a sanity check and more for the owner than the engine, but I am no expert on that subject.

CGr.

Another commercial made fuel : Fox "Duke's" fuel is 20% castor.

There is nothing wrong with commercial fuels. Heck, I don't have the storage area (secure and with ventilation) to make my own or I would. So, those of us that can't make it will gladly buy it.. even if the cost has gone up 50% in the past year. It's something we have to deal with. But, if you can manage to make it yourself, it's not that difficult (as a lot of Aussie's and Euro's will attest to) and works just fine.</p>

But, this goes beyond the point of the original post topic, doesn'***.And, yeah, I'mguilty ofadding the fuel issue,but I was trying to add to the content.Let's stick to the topic.</p>

CGr.</p>