Straick

I have an OS 18TM that has been eating both recoils and one way bearings lately. After the last one, I took the recoil off to fix it again, and found melted plastic from the recoil's spool(OWB locked to starter shaft and spun inside the spool) and a coppery looking paste inside the backplate's dished in area. After some further looking, I found that the starter shaft is loose in the backplate as well, so a new backplate and starter shaft have been ordered. I pulled the back plate, and everything inside looks normal, rod isn't loose and the crank can be turned over by grabbing the flywheel. The big question here is what caused this to happen? I have never let it run lean before and I followed the wear in as best I could from the manual that came with the engine. It's got about 3 gallons through it so far, and low on compression. I think that the low compression is from the air leak created by the bushing and shaft going bad on me, because I tune it every time I run it due to weather extremes. I currently plan on replacing the piston and sleeve this spring when it'll be warm enough to be able to break them in, but want to prevent this from happening again if possible. Thanks.

Bax

My Feedback: (11)

It sounds like you just don't have enough lubrication. If you're using a so-called "R/C Car" fuel, you likely have a very low oil content in the fuel. Most "car fuels" have 12%-14% oil content, which is really too low for your engine. You should use a fuel that has more oil content. O.S. typically recommends that you use a fuel with 18% oil content or better. That's the same as "airplane" fuel...and will prevent premature wear of the starter shaft at its bushing.

Straick

Thank you. The oil content could be why I've had nothing but trouble running Traxxas fuel, but other fuels ran beautifully. One final thing, is it safe to run airplane fuel in a car engine? I had heard not to because of the differences in the fuel.

Bax

My Feedback: (11)

"Airplane" fuel is just regular glow fuel. R/C car operators make a distinction because "Car" fuel has lower oil. "Airplane" fuel usually has 18% oil or so. "4-stroke" fuel has 16% oil or so. The only difference between the different fuels is oil content, but the ingredients are all the same...oil, methanol, nitromethane. The oil can be castor oil or a synthetic lubricant that works in model engines...there are different ones. In North America, Klotz synthetic oil is usually the one, and it's also mixed with castor oil....depending upon the blend being made.

"R/C car" fuel was developed by racers because it clears-out very well when throttle is applied. Car racers are on and off the throttle a lot and quickly. Airplane fliers are slower and smoother on the throttle. With a car, any hesitation when the throttle is changed can cost a race. Lower-oil fuels will clear very quickly and give faster throttle response. The low-oil fuel will provide lubrication as long as everything is ideal, however, get the slightest bit of dirt in the engine, a bit of air in the lines, some vibration-induced fuel foaming, and your mixture goes lean quite quickly. If you're a dedicated racer, though, an engine rebuild per racing weekend isn't out of the question. If you're a backyard "basher", then you want engine life over maximum performance.