well i have got quite a few hours of use out of my supertigre g-51, starts first flip and spinns a 12x4 at a respectible 13,500 rpm. i have noticed a leak in the front of the engine. the only thing i can think of is the bearing because that is the seal for the front end. its not a terrible leak, when it runs thier is a small drip about every 5 seconds or so and when i let it sit for a few hours i find a small puddle of fuel under the engine. nothing too bad, just a little annoying. my second questian is what i could do to the engine to maybe make it perform better. im running 10% fuel on a #8 plug. are thier any "aftermarket" parts i could put on it? or just any general tips or tricks to make it get a few more rpms would be appriciated. thanks for all your help in advance.

Don't worry about it. If it is fuel then it is siphoning from the tank into the carb while the plane is sitting. Most planes will do this if there is not much nose up attitude on the ground, especially when the tank is full.

It could also be carb spit accumulating around the front of the engine and dripping.

Our engines are designed to use a total loss oiling system. That is, the oil is intended to be blown away in the air stream. If some oil did not leak out of the front bearing area of the engine, the bearing would go bad because of lack of lubrication. Of course, an exceptionally loose fit (it happens) between the crankshaft and the crankcase bore can let more than normal amounts of oil leak.

How do you know if it is too much?

Simple. If the engine has normal fuel draw, it is not too much.

Glow engines, being total loss lubricated, are messy. Some mess is to be expected, unlike with gasoline engines.

Mikey,


As Kevin wrote, as to your first question, you shouldn't worry about a small fuel leak, since this is not an engine with a 'closed loop' lubrication system. The system is a 'total loss' type, where oil is consumed with the fuel.

The only problem you might encounter is am unsightly 'runny nose' and maybe difficulty shutting the engine down by closing the throttle fully.

About your second question, getting more power out of this engine; there are several tuned exhaust systems that will fit.
Jett offers the Jett-Stream and Turbo-Jett tuned mufflers, Nelson offers their UltraThrust and the MVVS has the #3248, which will fit with a suitable header and costs less.

You can also make a 'mousse can' magic muffler, which if you make your own header, will cost you very little.

ok, thanks for all the help. one more questian, approx. what rpm should it idle at and what should the top rpm be. i have a pitts style muffler on it right now and will look into a tuned pipe. thanks again

Well your on a 12x4 prop and that is 3D useage. If your not 3D ing and looking for more speed then a 11x6 would be in order. A cheap pipe would be the Tower 46 at $15 but has to be tweaked at mount to fit ST. Your on a pitts now so you may not have other pipe choices room.

I don't like engines leaking fuel as it sits. I consider the engine worn out if old, and junk if new. Course it's common with old designs, but not new ones. If it is covered on warrenty, and it's leaking from the front bearing, I suggest sending it back for some warrenty work. If they won't fix it then sell or replace the front bearing with one that has a good seal.

Hi!
A rubber seal or any other seal is not helping in this case. The leakage is due to the fact that the inner crankase to crankshaft surface is worn out or made with too large tolerances...no steel or rubber seal will fix that!
Remember the rubber/steel seals on a ball bearing is made to prevent dirt getting in or holding grease in...not holding glow fuel in!
Picture shows open, C4 bearings from Swiss company WIB the size all .40-.49 engines on the markert use (28x15x7mm) except Rossi.

Regards!
Jan K
Sweden

With model 2-stroke engines, some leakage is absoutely NORMAL. If you store your engine nose-down, then all the fuel residue/after-run oil in the crankcase will wind up either dribbling out the carburetor or through the front bearing. That's why I've always tied a rag around the front of the engine where the drive washer meets the case...or made some other arrangement to catch the drips. If anybody thinks these engines should be "dry", they need to spend a LOT more time working with them to learn about how they work.

You HAVE to have some oil pass through the front bearing to get it lubricated. As was stated in an earlier post, if your engine's running well, the leak's not serious to worry about. If the nose of the model is being wet with raw fuel, then the leak's worth worrying about. If you can just notice there is a leak, then forget about it.

The seal is not made by the bearing. The seal is made by the close fit between the crank and case between the carb and front bearing. If raw fuel is spraying out and the engine's operation is compromised or fuel consumption has gone 'way up, then the crank, case, or both need to be replaced to stop it.