Xplorer Ultraflight
Performance Paramotors
for powered paragliding

Problems Starting your 210 engine?
written by Keith Pickersgill

Does your motor give you a mule-kick when you try to pull-start?
Does it refuse to start or run very badly?
Read on...

This was written specifically for the popular Two-Ten engines, either the SOLO 210, or the Hirth 210 (F36) models. However, much of this applies equally to many other engines as used in powered paragliding.

This article was written in response to a desperate cry for help by a USA pilot whom was building his own backpack unit. I initially addressed his specific problem, but then went on to include all starting problems.

Written by Ben:
I have been having PROBLEMS with my Solo engine. It has always been hard to start. If you can get it started it appears to run and idle fine after adjusting the carb. At the present time it is almost impossible to start. It wants to kick back very hard. Many times it will rip the starter handle out of your hand. This leads me to think that it is a timming problem.

This problem is quite common, yet has a rediculously simple solution.

Tighten your drive belt!

Sounds crazy, I know, but we have seen dozens of similar cases, all solved by tightening the drive belt, or by adding some good quality belt-dressing to the belt.

If this does not help, then remove the two pulleys and have them acid-dipped by someone whom knows what they are doing! This increases the friction between the belt and the drive pulleys. Remember to remove the bearings and any other steel components before acid contact.

All that is happening, is you do not have enough rotational inertia to drive the piston through the compression stroke when it first fires.

Your propeller (and prop-hub) is an integral part of the "inertial flywheel". Without the prop, you will not easily start the engine. Likewise, if the belt is slipping somewhat, the prop's rotational inertia is not available to carry the piston through the intitial compression stroke after firing.

    Causes are any combination of:
  • belt not tight enough
  • belt in poor condition
  • oil/fuel traces on belt/pulleys
  • pulleys worn smooth from excessive belt slippage

The Solo 210, like the DK's engines and most other paramotor engines, have static timing i.e. same firing at idle and full power.

For ideal performance, the timing should be advanced (earlier) at high power.
At idle, it should fire at TDC (Top Dead Centre).

In the absence of this, the timing is pre-set halfway between the ideal for idle-speed; and high speed. The result is that it fires a tad too early at low rpm.

What is happening here, is that your pull-starting gets the motor turning just fast enough for the CDI to fire; the ignition takes place as the piston is still travelling upwards with not enough inertia, due to insufficient traction on the drive belt, causing the piston to be driven down before rotating through TDC (top dead centre), i.e. the engine tries to run in reverse, which of course it cannot do.

The result is a Mule-like kick, feels like ripping your arm out its socket.

    Other contributing factors:

  • Composite props are very light, with numerous advantages in flight, but less inertia to assist the starting. Wooden props make starting easier.

  • Some manufacturers are removing the flywheel to reduce the weight of the paramotor by 800 grams, relying purely on the crankshaft counterweights and the prop to provide sufficient inertia. This is not a good practise! It cheats on the spec-sheets by showing lighter than realistic paramotor weights, which seems to be a major selling point even though the weight is only apparent during a few moments of ground handling and is NOT an issue in flight.

There are other ways of making starting much easier, but I cannot divulge trade secrets here...
However,I will give some basic advice:

  • Replace your starter rope with a longer length, such that the reel is completely full when retracted. This makes a HUGE difference, as the reel diameter effects the "leverage" and effort required.

  • Proper pulling technique is essential. Here is how it is done -
    • take up the slack,
    • then pull slowly as the prop turns, until you are up against the compression stroke. This is the point from where you must start your pullstart stroke.
    • However, if the rope has been pulled out of the reel to some extent, you may not have much more length remaining for your pullstart stroke. To remedy this, slowly release the line to retract all the way, and again take up the slack.
    • You should now have a very-short line extended, and up against the compression stroke.
    • There are TWO techniques for the main pullstart stroke, once you have turned the motor to the compression stroke and have a nice short length to pull from.
      • The first is a gentle yet firm, long, accelerating stroke; you are only trying to get to firing RPM (usually 800 RPM) at the second cycle. The first cycle is simply used to accelerate up to speed.
      • The second technique is a short, powerful pull, the length of only your forearm, to get the motor up to sufficient RPM immediately. Different people are better at the one or the other, depending on your physique.

  • Clean out all the magnetic debris and dirt inside the magneto area. They cause complications and lead to erratic problems.

  • Cut away some of the black starter cover material to give the rope free run without chaffing on the brass grommet.

  • Settings make a huge difference. Here are the correct settings:-
    • Spark Plug must be B6HS or equivalent (on the Two-Ten engines), set to 0.6 mm gap.
    • Timing is fixed, but check if your woodruff key is undamaged, otherwise the stator-wheel (bolted onto the flywheel) may be out by a few degrees, upsetting the timing.
    • Magneto clearance must be 0.2mm on both sides.
      Let me clarify this. The coil is U-shaped and the two tips must each be 0.2mm from the magnets on the stator-wheel. Make absolutely sure you are setting against the magnets, and not the counterweight on the opposite side of the butterfly shaped stator. If you do this, the magnets will collide with the coil, destroying it. Use two seperate 0.2mm keys under each tip, and let the magnets pull the coil up against them (with the key seperating the two) before you tighten the two locking screws.
    • The carb air-mixtures can obviously only be set once the motor is running, but there is another setting very few know about (another trade secret...) This is the carb pop-off pressure, critical on all diaphragm carbs, e.g. Walbro, Tillotson, etc. You need a pop-off gauge, but you can make one using a cheap pressure gauge (approx 2 Bar max) and a pump of sorts. Try the squeeze bulb from a medical Sphygmomomenometer (blood pressure monitor). The design is a T-junction, with pump on any leg, gauge on another, and a short (3cm or so) piece of 6mm silicone fuel tubing on the last, which you fit on the fuel inlet of the carb.

        Here is the procedure:
      • First prime the carb to ensure it is filled with fuel.
      • Then remove the fuel line from the carb and replace with the pop-off tester.
      • Slowly pump, as the guage increases.
      • Stop at about 0.5BAR (7 PSI)
      • The needle should NOT drop noticibly over a few seconds. If it does, the engine is prone to flooding. The needle-valve and valve-seat need replacing (a few dollars).
      • Having established that the needle-valve will not flood the engine, now slowly increase the pressure until the needle-valve in the carb opens (pops-off) and the pressure drops sharply. This should happen at around 0.6 to 0.8 Bar, or 9 to 12.5 PSI

        Usually, it pops-off too early; remedy by replacing the valve spring (a few cents) with a calibrated replacement. Every carb spares supplier will carry these in stock. In an emergency, the old spring can be stretched very slightly and re-tested as above.

        If it pops-off too early, the motor will tend to run rich, no matter how you set the mixture screws.

        If it pops-off at too high a pressure, the engine will run lean and risk overheating and seizure.

Another possible problem: My, there are lots of them, aren't there?

If the oil-seals at either end of the crankshaft leaks, then you will have great problems, sometimes in-explicable sporadic complications and will waste lots of time searching elsewhere. At low power, fuel/oil/air will escape, and at higher RPM it may suck in excess air through the leaking oil-seal. Replacement seals are a couple of dollars each, from any oilseal supplier.

Quick-check for leaking oil seals: remove the carb and exhaust. Pour fuel-mixture (yes, with your 2-stroke oil) into the carb, until the level is at the inlet port, i.e. way above the crankshaft level. Now look for fuel running out at either end of the crankshaft. The propeller end is easy, but the starter end will be easier spotted if you first remove the entire starter assembly. Remember to re-set the magneto clearance when you re-install.

Any leakage at all warrants oil-seal replacement. You need not open the crankcase to do this. The old seals can be pulled out with a simple tool made from some stout wire into three legs (like a wheel puller) which penetrate through the old seal (destroying them) and gradually wiggle them free. The new seals can be easily eased into place if you use enough oil on the crankshaft. Total time, 20 minutes.

Last word of advice: When priming, tilt the entire engine toward the carb (15 degrees or more) and prime until fuel drips out of the air-filter. Let it stand like that for about 15 seconds, then upright for another 15 seconds with throttle wide open, then release the throttle and start your pull-start procedure.

This practise ensures the carb has indeed been primed fully, and prevents any excess fuel from running into the engine and flooding it. The excess runs out the carb via the airfilter instead.

Always start with the throttle at idle, unless you have assistants whom can hold the motor firm, and a reliable buddy whom can hold the throttle slightly open (15-20%) and will release to idle the moment it starts.

Never try to hold the throttle open by yourself and pullstart. When the engine starts, it will start thrusting toward you and you will be forced to "push back", which will invariably cause you to un-intentionally squeeze the throttle to full power, and you will be trapped into a runaway situation. If you release the throttle, you will be forced to release your grip on the thrusting motor with disastrous results. We had such a case recently with the pilot severly damaging his left arm which was mangled by the prop, resembling a serious shark attack.

I hope this helps Ben and all the others with similar problems.

Address comment to Keith Pickersgill at keith@xplorer.co.za