Priming & starting paramotors

By Had Robinson
updated August 12, 2019

Introduction

Here is how to prime a stock paramotor engine so it will start the first pull – every time.  This technique will not flood the engine.  Pilots must be able to easily position the inlet side of the carburetor lower than outlet side.  Note:  With engines where the carburetor is mounted vertically e.g. the Minari, a slightly different technique must be used – see below.

If you do not know the parts of a carburetor, study this diagram of the WG-8 carburetor or the WB-37 carburetor.  Note that the diagrams are of generic WG and WB series carburetors and that the actual shape of some parts of your carburetor may be slightly different, such as the metering diaphragm cover and the fuel pump cover.

The priming lever (or spring) is not present in the official diagrams of the carburetors.  Depending on the model carburetor, it may be missing entirely or look like either of the following photos.  If it is missing, use a broken toothpick to push down on the metering diaphragm beneath the cover.  Thankfully, a pilot cannot easily damage the ML diaphragm by pushing on it through the hole.  It is strongly recommended that a priming lever be installed.

WG8 carburetor priming lever

or

Walbro WG-8 priming lever

A flooded engine will take a lot of pulling on the starter to clear things up.  It may be so flooded that the engine will require the carburetor and reed valve be removed in order to drain out the accumulated fuel and oil.  Frustrated pilots routinely damage their starters trying to start flooded engines.

Additionally, using the technique given on this page will also tell pilots that the fuel system is in good condition.  (Go here to get more info on how to easily test the fuel system.)

No engine will start easily unless the ignition and carburetor adjustments are in good order so be sure these are OK first if you have been having starting problems or it has been more than a year.  The low speed idle adjustment is precise and needs to be accurate for the engine to start or run smoothly midrange.  A broken core in the secondary wire, a fouled, old, or loose spark plug, or bad/old fuel will always make the engine hard or impossible to start.  If it has been more than a year since the carburetor has been rebuilt, it MUST be done.  All fuels are hard on the flexible parts of the carburetor, especially ethanol blends.

Non-flash starters   If your starter is not the flash type, a bit more strength is required (unless it is an 80cc engine).  Proper priming is even more important to ensure that the engine starts the first time.  The ignition timing on all 2 stroke engines is always advanced by 15 degrees or so (the plug fires 15 degrees before the piston reaches top dead center TDC).  This means that a the engine may kick badly or be hard to pull through TDC.  This means that the priming technique is more critical to make starting the engine easy.  It is better to under-prime some because the "kick" will be weaker (less fuel).  When pulling on the starter, pilots will find it may pull through TDC fairly easy and start if they go easy on the prime.  Of course, if the engine is flooded it will also pull through TDC easily.  Pilots will have to experiment and keep close attention to how many seconds they press the priming lever down for.  Start with just 2-3 seconds and work up from there.  Speed does not help that much as the ignition systems will make a spark.  A steady pull is the best and it can be done the safest by having the engine on the back.  A clogged decompression port (DCP) will also make starting the engine extremely difficult.  It can only take (50) hours or less for the port to clog.  Keep records of when it was last cleaned.

Leaks in any part of the fuel system will make the engine harder to start and can lean it out at the high end.  This often causes engines to burn up!

 If the engine is properly primed, it will start.

Warning: If pilots must start the engine on the ground, ALWAYS put the throttle hand on the engine frame in such a way that the sudden start of the motor does not cause the throttle to increase accidently!  Larger engines can be terrifying if they go even 1/3 throttle, much less full throttle.

BE CERTAIN THAT THE THROTTLE IS IN YOUR HAND WITH YOUR THUMB READY ON THE KILL BUTTON!

A run-away paramotor is both terrifying and dangerous and pilots must always be ready to shut it down.  (Don't ask me how I know this....)  Kill switches can fail.  This is why newer pilots should use their glider strap or a line to tie the propeller to the cage (clutched engines only) until they get thoroughly familiar with their engine. 
Miniplane-USA supplies propeller covers with a strap for this purpose.  None of this is necessary, however, if the engine is started while on the back.

Jeff Goin, President of the USPPA has these warnings about starting a paramotor.  Don't be an idiot!  (Yours truly is working on it....)
  1. Time limit – This technique is only good for about (5) minutes because the fuel will evaporate and the prime will be lost.  Modify the times given in the steps below for your particular engine, as needed.
  2. Fuel line to the carburetor – It must be visible so you can see when the fuel is clear of air or bubbles and a solid stream of fuel is entering the carburetor.  It greatly helps to extend the priming tube with a 6" piece of 5/16" OD polyethylene tubing or windshield washer tubing so the fuel line is more visible. 
  3. Tilt the paramotor – Facing the rear of the engine, tilt the paramotor to the right about 20 degrees so that the intake of the carburetor is just pointing down from the engine side.  Note: This step cannot be done on engines with vertical carburetors!  If this is not done, the engine can flood.   The principle is that extra fuel will run harmlessly out of the carburetor instead of into the engine, flooding it.  However, do not tilt it excessively because you want some fuel to be present in and about the carburetor throat.
  4. Blow into the priming tube on the fuel tank as hard as you can.  Use the tip of the tongue to hold the pressure.  There has to be enough air pressure to raise the fuel in the tank about 18" (the distance from a nearly empty fuel tank up to the carburetor on the engine).  If you have a primer bulb, squeeze it repeatedly until resistance is felt, then squeeze again and hold it while performing the next step.
  5. Push down on the priming lever (a.k.a. the "primer spring") on the carburetor for 5-8 seconds.  If there are bubbles or no fuel in the line going into the carburetor, more time will be required to purge the fuel system of air.  If nothing happens you may not have blown hard enough into the priming tube.  (If there is no priming lever, order one from Miniplane USA or use a toothpick.)  Hold the lever (and fuel tank pressure) until ALL the larger air/vapor bubbles in the fuel line go into the carburetor and then hold it another (4-5) seconds.  If there is air in the system you may be able to hear it go past the metering valve (a hissing sound).

    If you are using cheap fuel or the weather is hot, you may not be able to get rid of the vapor bubbles (not air bubbles) in the fuel system.  The vapor bubbles can be so many that the engine may become starved of fuel and will not start.  Pouring cold water over the carburetor and fuel tank will fix this problem temporarily enough to start the engine and launch.  If the priming lever is held down too long, causing fuel to go everywhere, it does not matter because the fuel will harmlessly accumulate in the airbox and/or run out of it.  The engine will not flood.  Most pilots do not prime the engine long enough.  As you repeatedly perform this step, you will become familiar with your engine and better able to adjust precisely the time needed to hold down the priming lever.

    If there is a foam-type filter in the air box, the system will be more sensitive to flooding, even with this technique.  If there is enough fuel that has flooded into the filter, the fuel vapor can saturate the space inside the filter so that the engine acts like it is flooded.  In such a case, you may have to be more careful experimenting with the number of seconds needed to hold down the priming lever.   

    Minari and others with a vertical carburetor: hold the priming lever down for about 5 seconds.  This assumes that the fuel system is purged of air.  If it does have air or bubbles, hold the lever down to complete the purge and then another 3-5 seconds.  It is easy to flood these types of engines.  You will have to get familiar with how your engine works.  How many seconds you need to hold the priming lever down can vary but you will learn how your carburetor and engine function so as to get just the right amount of fuel in the engine to prime it.

    Most engines  If the air box is removed, you can watch fuel dribble out of the carburetor (except the Minari where it dribbles into the engine and floods it).  If it does not, you know you have a fuel system problem and the engine will never start until it is fixed.  Note: the fuel filter will always have some air/fuel vapor in it.  It rarely means that there is a fuel system leak.

    THE ENGINE MUST BE STARTED WITHIN A FEW MINUTES OR THE PREVIOUS STEPS MUST BE REPEATED.  THIS IS BECAUSE THE FUEL WILL EVAPORATE FROM THE CARBURETOR THROAT AND AIRBOX AND THE PRIME WILL BE LOST.
  6. No choke – do not use the choke.  It is unnecessary if the engine is primed correctly.  When this technique for starting the engine is mastered, the choke is not used except to stop the engine in an emergency (failed kill switch), to start it mid-air after the engine has been stopped for 5-10 minutes or more, or if you are unable to prime the engine for some reason.
  7. Put the paramotor on your back.  This is optional but very smart if you have a large engine.  It is unnecessary to start it while it is on the ground and always safer to start it on your back.  However, if you did not prime it correctly, you will have to remove the engine from your back and start over which can be a nuisance.
  8. Slowly turn the engine over 3-4 times with the manual starter.  It takes little effort if done slowly enough.  This will charge the crankcase and cylinder with the fuel/air mixture.  If you do not have a manual starter, skip this step.
  9. Open the throttle about one quarter but only after you first test it for function.  ALWAYS SQUEEZE THE THROTTLE TO FULL A FEW TIMES AND FEEL IT RETURN TO IDLE!  You must be sure that the throttle is working properly.  A stuck, wide-open throttle is the most terrifying thing a pilot will ever experience.
  10. Non-flash starters only – Pull slowly on the starter rope until the compression stroke of the engine is felt.  Hold the starter in this position for a few seconds.  You want the piston to be about an inch before the top of the cylinder with no pressure in the cylinder.  Holding it a moment allows the pressure to bleed off.  Be certain to let the starter rope retract fully before continuing with the next step.
  11. Flash starters only Pull smoothly and steadily on the starter to turn the engine over.  NEVER YANK ON THE STARTER.  It should immediately fire and start running.  Do not pull so far that the starter cord is pulled to the end.  If it is pulled to the end regularly, full strength used, the pull handle yanked, or pulled repeatedly, the starter can be damaged.  Remember that anything amiss with your carburetor or ignition is not cured by repeated attempts to start the engine.
  12. Electric starters Hold the start button down until the engine starts.

The engine can be hot or cold.  If it does not start the first pull, you probably did not prime it long enough.  It may take a few times for you to master the idiosyncrasies of your carburetor/engine combination.

A flooded engine may have to have the spark plug and air box removed, the throttle tied open, and an hour to sit for things to dry out.  I have seen engines so badly flooded that I had to remove the spark plug, turn the engine with the open cylinder head pointing down, and crank the engine while watching the fuel pour out of the cylinder.  This can happen if step #1 above is not done correctly.  If an engine is mildly flooded, open the throttle fully and slowly and fully pull on the starter 5 or 6 times and then attempt to start.  If this does not work, remove the spark plug and crank the engine 5 or 6 times.  Let the spark plug dry a bit, reinstall it, and try again.  As often as not, there was an ignition problem on the flooded engine.  You are certain your ignition system is 100% in order, right?

If a pilot is careful, the starter will also last much longer – even the life of the engine.  I have never had to replace a starter on my Top 80, only the cord after a few hundred hours of use.

Turkey Vulture

USHPA
USPPA