I just got a Hobbico Avistar(with and OS .40 LA engine) from Tower Hobbies. After flying for several months on realflight, I decided i was ready to solo(dumb idea). Well, I broke in the motor about 5 tanks of gas, very very rich. I flew 8 successful flights and now my engine is very noisy. At low RPM it rattles really loud. It also has a lot of end-play in the crank. The sound goes away at higher throttle settings though. I know it is a LA with oilite bushings instead of ball bearings, is that noise normal for these engines?

Thanks,
Brandon

Some rattle at idle and mid range is normal with the LA engine. A little crankshaft slop is usually normal as well. Of course since I can't hear your engine, I can't promise you that your rattle is normal, but I can tell you that the LA's I have owned do rattle at lower rpms. Good little engines though. Not big on power, but usually pretty reliable and will take a pretty good lickin and keep on tickin. The O.S LA engines remind of the old ford 300 6 cylinder engine. The lifters will hammer and rattle, the engine might smoke and be plum wore out, but it will just keep going and going!

My first trainer had an la 40 as well. I believe that mine had a little play in the crank too, but it shouldn't rattle. Make sure that the muffler screws are tight first, then check the other screws on the motor. If that doesn't work, you probably have a bent crank. Have a fellow club member take a look at it. If you aren't in a club, join one. Best $25 or so you'll ever spend.

It's not just LA's but any plain bearing engine tends to rattle a little at low throttle settings. There's nothing to stop the crankshaft moving backwards and forwards and they must have a small amount of movement to allow for the crankcase expanding slightly as it warms up. The rattle goes away as the revs increase because the extra thrust from the prop holds the crankshaft forward. Don't lose that steel shim washer that fits between the crankcase and the prop driver though. It sets the amount of free play but more importantly it stops the crankcase getting worn out when you use an electric starter.

As kangaroo and downunder have already indicated, many bushing engines can and do develop a little rattle at low idle. No worries. A few years back we had a going little event for pylon racers using the K&B .28 Sportsters a delightful little engine known locally as "Teakettles". You know what, the noisiest of the teakettles were always the best engines and tended to always be the winners!

I still have some of those nifty little teakettles going strong fifteen years latter.

John

Hmm... It didn't rattle till after I changed props... Mabey I lost the washer? I don't think so though, because I never pulled the spinner backplate off. Its more like a buzz or clack than a rattle. I checked everything on it, it's all tight. Also, when I first got the plane, I loc-tited all of the engine and mount hardware, so if i missed checking something, its loc-tited anyway. So it's normal for these?

Rattle is normal for all bushing engines. Some will make more noise that others. To reduce the noise as much as possible, go to a fuel that has a major part of the oil package being castor oil. Synthetic-oil fuels will allow the engine to be noisier. If your oil mix is all-castor, then the noise will diminish over time as a slight varnish will build up between the case and the crankshaft counterweight.

Don't worry about it, though. It's not going to hurt anything.

Take Bax's advice here, and just run the thing. IT IS NORMAL FOR THEM TO RATTLE SOME! If you send it off to Hobby services they will just send it back to you because it is typical for a bushing engine to rattle some especially at lower RPM's. If you are running Full synthetic fuel and the rattle bothers you, then also do as Bax suggest and buy some fuel with Castor, or I would recommend instead of wasting the fuel you have to just add about 2 fluid ounces of 100% Castor per gallon of fuel. Bakers Castor is fine, or you can order a bottle of Klotz to add to your syn fuel. The engine will quiet down with the castor in the fuel over time, but you will trade off this benefit by having a tarnished looking engine, and more mess on the Plane itself to clean.

I know this fellow was trying to be helpfull, but I would not worry about your crank being bent unless it developed clanking noise after it was plowed into the ground nose first at 50 mph. Even in those cases I have seen these engines picked out of the ground with a screwdriver, cleaned out, and put right back into service. So unless the engine has suffered some severe crash and developed a noise directly after, then more than likely it is fine and the noise you hear is normal!