Ethanol: Your Small Engine Worst Nightmare

I am sure at some point, you have heard someone saying how horrible Ethanol is for your engine.  Ethanol has become more common the last few years, starting in the Midwest states and now seems to be everywhere, and whether we like it or not, it seems as if it is here to stay and is going to be used a lot more.

Ethanol is absolutely terrible for small engines.  Why just small engines and not just all engines?  Because the automotive industry is worlds ahead in ethanol technology and lawn and garden companies are trying to play catch up.

What does Ethanol do?

The worst thing Ethanol does, it attract water.  Not only does it attract water, it sucks it through your fuel lines and gaskets, causing them to swell and deteriorate.  So not only are you pulling in a non-flammable substance into something that's whole purpose is combustion, you are destroying the engine components that are vital to operation.  Secondly, small engines still have carburetors, as do older vehicles.  Ethanol will also destroy your carburetor.  The quickest that I have seen this happen, is in one tank of gas.  The ethanol separates from the gas (phase separation , attracts water, and clogs fuel jets within the carburetor, and can cause your needle valve to stick.  Third, it lowers that octane of your fuel, so 87 Octane, is now more around 84 octane.  Finally, related to the octane rating, Ethanol causes lean running conditions. Lean, means hot, which mean a whole world of engine problems.

So, what can you do?

Small engine manufactures have begun advising everyone to use AT LEAST 89 octane fuel.  Now, this still have Ethanol in it, but it is still better.  It will start at a higher octane, so as it sits and degrades, it will still have a high enough octane to not cause damage to the engine.  There are also multiple Ethanol treatments and Fuel stabilizers available on the market today.  The two that I work with the most is K100 and Restore USA's fuel treatment.  These Ethanol treatments prevent phase separation, and maintain a higher octane level over longer time spans.  Do not use Sta-Bil, I have seen engines come in that have run fine for years, and then the operator has added Sta-Bil, concerned that his engine will stop working.  The reason I know it was Sta-Bil and not Ethanol is because it discolors the gas as well as the fuel filter, and will gum your carburetor.

Are there still stations that sell ethanol free gas?

Sure are, they are rare and far between, and becoming further in between a lot quicker, but there are still a few out there. If you are filling up at an unfamiliar station though, pay close attention to what the pumps say.  Why you may ask? Because the stations that I have seen that have E85 available, are not very well marked, and putting E85 into a non Flexfuel vehicle, let alone a small engine, will ruin your engine.

The picture shown is what ethanol combined with Sta-Bil will do to a carburetor. 

Tricks to Replacing a Valve Guide

Engine parts wear, although, most things that are metal coming in constant contact with other things that are metal will wear.  One part that will leave your engine in a not so well operating state is a worn valve guide.

This is the part of the head (in the case of an over-head valve engine) or block (in the case of a L-head engine) that the valve travels up and down in while opening and closing.

Now, getting the old worn guide out is relatively easy, you can pound it out, heat and press it, grind it out, as long as you do not hurt the engine component that it sits in.  Getting the new one in can be a little bit more tricky.

The one trick that I picked up and use most often, I feel works the best and is the easiest.  First, you are going to put your new valve guide in the freezer until it is frozen solid.  Once that is done, you want to start heating the seat (I typically use a propane torch or a acetylene torch).  Now going off of the presumption that common sense is in fact not so common I will explain why.

The new valve guide must fit inside the seat, so it must be small enough o fit in, but snug enough not to fall out under normal use.  Freezing the guide will cause the metal to shrink, while heating the seat will cause it to expand.  Thus, making the guide slip more easily into position.

Once the guide is frozen and the seat is heated and everything is ready, place the guide into the seat (take extra precaution to ensure that it is completely straight).  With a towel over the guide (protecting it from mushrooming and ruining it), pound it into place (the use of a impact socket provides a nice contact surface and displaces the force evenly across the top of the guide).  Pound the guide until it is perfectly flush with the surface.

The engine is now ready to reassemble.

Thrown Valve Seat

Today at work, we had a customer bring in the head of his engine, with a thrown valve seat.  Usually once an engine throws a valve seat, it means its time to replace the head, but there is a trick you can do to try and save the head, and it is success more often than not.

First thing you must do is obviously remove the head and valve covers.  Before doing anything further to repair the seat, you should check the head and engine block to ensure that they are not warped and need replaced anyways [To check levelness of the head, use a flat surface (a plate of glass), and a feeler gauge.  Set the head on the glass and feel around the edges with a .003 in. feeler gauge.  If it does not slip between the head and glass, your head is level, if it does, depending on how badly warped the head is, you can use a fine grit metallic sandpaper laid on your flat surface to shave the head until level.]

Once you are certain that the head is level, clean the head and the valves with a wire wheel or buffer disks (I usually prefer starting with the wire wheel to get the majority of carbon build up off, and then put a nice smooth finish on it with a buffer disk).  You will also need to clean the valves and the valve seats.

Once the thrown seat is clean, use a grinding wheel or coarse sand paper to lightly rough the outer edge and the bottom of the seat.  Now, you will mix a high temperature adhesive (We use JB Quick Weld) and apply it to the outside and bottom of the seat, and put it in place.  Using a socket (Deep well impact sockets usually work best) lightly tap the seat into place until it is flush with the surface of the head.  As an extra precaution, using a center punch, go around the seat, about 1/8 in. out, and tap the head in 1/8 in. intervals all the way around the seat.  This will force the metal of the head around the seat to mushroom slightly over top the seat, holding it in place.

Next, you want to take a fine valve grinding compound and smear it on the valve.  Insert the valve into the seat, and rotate it back and forth, "lapping" the valve and valve seat.  By checking the wear marks made from the compound on the valve and seat, you can tell whether the seat needs to be recut or the valve needs replaced.  If everything is as it should be, you're finally ready to reassemble the engine.

Gasoline Four Cycle Engines (Four Stroke)

Four cycle engines, also known as four stroke, are the engines that most people are familiar with.  Four cycle engines are found in vehicles, tractors, and most lawn mowers.  Diesel engines can also be classified as four cycle engines, even though they are slightly different to the gasoline four cycle engines.  Unlike gas operated two cycle engines, four cycle engines have an oil reserve in the crankcase, providing constant lubrication of moving engine parts, as well as valves and a cam shaft.  Although there are more moving parts to these engines, their operation is still rather basic.  As your crankshaft turns (the part of the engine that converts the power of combustion to usable energy), it moves the piston up and down through the cylinder.  The crankshaft  also plays another vital key to the engine operation.  As it turns, the spline gear on the shaft engages your camshaft, which has lobes on the shaft itself with controls the opening and closing of your valves. As the camshaft turns the lobes come into contact with tapits, which push against your valve guide rod opening and closing the valves in sequence.

There are four stages in a four cycle engine operation, hence it being a four cycle engine.  The first is intake.  As your crankshaft and camshaft rotate, the camshaft opens the intake valve as the crankshaft pulls the piston away from the cylinder head, creating a vacuum which draws the atomized fuel-air mixture into the combustion chamber.  Once the piston reaches top dead bottom (TDB), it begins the second stage, compression.  [During this stage, the intake valve is open while the exhaust valve is closed, and the piston is fully retracted]

The camshaft closes the intake valve as the piston begins moving back towards the cylinder head.  As the cylinder approaches top dead center (TDC), it compresses and heats the fuel-air mixture, making for easier combustion  After reaching TDC, the mixture is ready for the next stage, combustion (also known as the power stroke).  [During this stage both valves are closed, and the piston is fully extended into the cylinder]

Now the the fuel-air mixture is ready to do its job, the ignition coil discharges, sending 20,000 volts through the ignition wire to the spark plug, igniting the fuel-air mixture. NOTE:  This is not an explosion.  As the spark reaches the diodes, it ignites the mixtures and a flame front spreads throughout the cylinder.  This build up in pressure forces the piston back down towards the crankcase, while rotating the crankshaft, which is what powers whatever you have attached to the engine.  As the piston reached TDB, the camshaft opens the exhaust valve, preparing the engine for the final stage, exhaust. [During this stage both valves remain closed until the end, and the piston is fully retracted]

Now that the cylinder has went through its power stroke, it must expel the waste from the cylinder in perpetration to fire again. At the end of the power stroke, the exhaust valve had opened, allowing gasses to escape.  During the exhaust stroke, the piston moves back towards the head, forcing the remaining gasses and carbon out of the cylinder.  Once reaching TDC, the exhaust valve closes, and the cylinder is ready for the intake stroke. [During this stage, the exhaust valve is open while the intake valve is closed, and the piton returns to TDC]

Here is a link to an animated version of a four stroke engine showing the crankshaft, camshaft, and valves during operation:    http://www.animatedengines.com/otto.html

Why I am Blogging

Hello everyone, I am Aaron Remai.  I am 23 years old and have been working as a mechanic for almost a year now.  I have my Expert Technician certification from Kohler engines, which is the highest rating you can achieve, and am currently working towards earning my Master Mechanic certification through Briggs and Stratton.  In that time I have already seen quite a few things that my boss, who has been in the industry for 13 years, was just seeing for the first time as I was.  This just goes to show that no matter how long you have been doing something, there is always a good chance you can still be surprised.  The purpose of this blog is to hopefully give a little bit of insight into how engines work in general, whether they be a passenger vehicle, diesel, four cycle, or two cycle.  As I get further into my blog, I hope to begin giving step by step how to's and eventually instructional videos.  I hope that as I post more and more, that you will enjoy reading my blog, and will be able to find information that you are looking for.  If you have any questions about how to do something or how something works, feel free to contact me and I will do my best to respond in a timely fashion.