BG's Engine Clinic

Service Tips


(Also known as our "Did You Know..?" section)


Did you know?  Running your lawn equipment at full throttle results in better fuel economy. Most modern engines are designed with two specific power ranges in mind - Idle, and Full Throttle.  When you operate your engine outside of the engineered top RPM power range, several things happen: First off, your engine has to work harder to do the same work, decreasing fuel economy and performance. Secondly, whatever the engine is powering was engineered at the factory to run at full throttle. Reduced engine speeds cause poor performance of the equipment.  If you need to adjust the forward speed of your tractor, change gears or change transmission range. 


Another reason you should always run at full throttle is to help the engine maintain the engineered operating temperature - Reduced engine speed reduces the cooling air flow over the cooling fins, which can cause overheating and reduced engine life.  It also reduces the amount of oil being circulated to lubricate the engine, which also can cause shortened engine life.


Finally, on engines that are equipped with electric start and battery, the engine needs to run at full throttle in order for the alternator stator to produce enough voltage to charge the battery. Quite often we will see a tractor that keeps having battery failures or dead batteries that is traced to the user operating the equipment at part throttle.


Every manufacturer of air-cooled engines recommends that engines be operated at the full throttle setting (top governed RPM) for best performance and longer engine life.


Did you know? While you may see many advertisements warning off the dire consequences of ethanol blended fuel, the current government regulations 1 state fuel may be blended with *UP TO* 10% ethanol. (See footnote). What this means:  All power equipment manufacturers state that warranty is void when operated on greater than 10% ethanol.. but most any gas you buy will be well within that range.


(For detailed information, see our full article on motor moonshine)


1. - Footnote - This has changed on October 13,2010- A ruling by the EPA that allows up to 15% ethanol blends, so this issue is now a *very real* concern. It is already a big issue in the Outdoor Power Equipment industry.


So, how CAN you tell whether the fuel you are using is safe for your power equipment or not? If you suspect that the gas you are using may have too much ethanol, you can purchase a low-cost alcohol fuel tester - the kit works pretty simply: Fill to the specified line with clean water, and then fill the rest of it with the suspect fuel, and let it stand for 5-10 minutes. If the water level appears to have increased beyond the 10% mark on the tester, then your fuel contains too much ethanol.


Did you know?   Gum and Varnish can form in fuel as it ages, even in as little as 2-3 months. What's Varnish?  Varnish looks like.. well. varnish - a brownish translucent film of hardened material that builds up like plaque on teeth - when it starts to flake off, it plugs up fuel passages and fuel filters.  Gum is a sticky jelly-like substance that also builds up in fuel systems, which can collect dirt, and coalesce (like plaque in your arteries) until it plugs up a fuel passage - this is most often the tiny fuel jets in the carburetor.  When equipment is run and used regularly, the movement off fuel through the fuel system helps to "scrub" these passages and keep things running fine, but when allowed to sit for extended periods (such as weedeaters stored all winter, or snowblowers stored all summer), this is what causes many of the problems we see in spring and fall.We've seen a couple of snowblowers that we have to rebuild the carburetor and clean the fuel tank every year due to this issue.


Preventing this build up can be achieved by many methods, including starting and running your equipment on a regular basis for 10-15 minutes or so, once a month. Addition of fuel stabilizers  can also help extend the storage life of your fuel.  Another method people have used is if your equipment has a fuel shut-off - simply turn off the fuel and let your equipment run out of gas. (PLEASE DON'T DO THIS WITH DIESEL ENGINES - They very likely wont start again and will require a service call!) While that doesnt keep fuel ffrom breaking down, it does tend to restrict any deposit build up to the fuel tank, and the fuel filter will strain that stuff out the next time. (if there is a fuel filter, that is..)


A good rule of thumb: Never buy more gasoline than you can use in a month. If you do, pick up a bottle or two of fuel stabilizer , which helps your fuel stay fresh in storage longer.


A last note on using fuel stabilizer: Don't bother using it in old fuel you already have on hand - it will not do any good. Fuel stabilizer works best when mixed with clean, *fresh* gasoline. It will not magically "restore" old gasoline to "fresh" - at best it will only keep the old gas from degrading further.


Did you know?  Engine oil breaks down over time, just like fuel. So, even if you have a brand new bottle of engine oil , if it has been sitting on the shelf for 2 or 3 years, it may look clean and fresh, but using this oil when changing your engine oil may be just as bad as not changing the oil at all!  If you like to stock up on oil for oil changes, don't buy more than you might use in a year. - if you DO happen to have a bottle of old (but new) motor oil sitting on your shelf, you can always use it for oiling foam air filter elements (if you have any that require oiling) or use it for other lubrication purposes. Alternatively you can take it to a used oil collection center.


Did you know? Your spark plugs may look clean and fresh, but even a brand-new spark plug has been known to "short out" from time to time.. Like with any electrical part on the planet, just because it is brand-new, does not mean it's Good!  If you have any doubt, get a second "new" part and test that, or bring it in to the shop, and we can hook it up to specialized test equipment or a known running unit and verify that the part is indeed a good part. That "But, it's a BRAND NEW part!?" issue has many times tripped up even a seasoned professional mechanic ,  - so it is always a good thing to keep in mind: Just because it is new, does not mean it is good.  In most cases, such parts are covered by a warranty, but sometimes an improper installation of a part will cause it to fail immediately, and these are not warranty failures.


Did you know?  If you shut off your equipment and regularly get a loud "bang" or backfire (correctly called afterfire) , this may mean your equipment is due for a tune-up and carbon cleaning.  When you shut off the engine, the spark goes away immediately, however the engine may continue to rotate a few more times, and this will pull fuel through the carburetor into the combustion chamber - If there is carbon build-up in the combustion chamber or on the valves, the carbon can still be red-hot and ignite the fuel mixture, causing the backfire (most often backfire through the muffler, since the exhaust side will be far hotter).  A properly tuned engine can help to reduce this issue in many cases (air filter, carburetor cleaning & adjustment, governed RPM adjustment) , and sometimes the problem can be controlled by allowing the engine to run at idle speed for a few minutes before shut-down, allowing the superheated carbon time to cool sufficently that it does not ignite the fuel. However, the problem will only get worse, until the engine is serviced and carbon cleaning and/or valve job is completed (during which the carburetor and fuel system will probably be checked and cleaned as well, anyway).

This is the reason that many newer lawn tractor engines are equipped with a solenoid on the carburetor - It is an anti-afterfire solenoid, it DOES NOT sut off fuel flow from the gas tank! It simply blocks off the main fuel supply jet so the engine will not draw fuel into the cylinder while it is coasting to a stop.


 Did you know? The Windows in Kerosene heaters are made of Mica (A type of silicate mineral resistant to high temperatures.) If your mica window is broken or missing, it can cause many burning problems, including odors, poor burning, flickering flames, "spitting" noises from the wick and burner chimney, etc.


  •  A variety of sizes of mica are available to fit any type of kerosene heater and many wood stoves.
  • Replacement of broken mica windows can make seemingly large burning problems just a minor, inexpensive repair.
  • Well-maintained mica windows insure proper air flow and cleaner combustion and help avoid unnecessary odors and hazards.


Welcome to BG's Engine Clinic, where we help to put the POWER back in POWER EQUIPMENT.
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Motor Moonshine - Our article on Ethanol Blended Fuels and Outdoor Power Equipment

Motor Moonshine   What's up with Ethanol?   O.E.M. Manufacturers, warranty, and Ethanol   What does Ethanol do to my lawnmower?   What if it's older gas? It looks OK,...

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