launch at Valle de Bravo, Mexico powered paraglider launching from Evergreen Turf farms


paragliding training center

Polini Flash starter problems & fixes

by Had Robinson

Important update

September 2018 – Polini is now selling the Thor 190 flash starter internals for use in the Thor 100 & 130.  There are more turns in the flash spring for the 190.  Polini has also beefed up the method to hold the flash spring in the house.  More needs to be done but this helps.



  1. Use nitrile gloves.  Working with springs can be dangerous.  Wear eye protection.

  2. Remove starter from engine – The best way to do this is to disconnect the lower parts of the harness from the engine frame and then flip up the harness and hold it with some cord against the front of the upper cage.  Remove the (6) 5mm screws that hold the back plate to the frame.  You now have complete access to the starter.  Remove the (4) screws that hold the starter to the engine.  If you have the special lower screw that has a nut on it, it is MUCH easier to gain access to the rear of the engine if you drop the fuel tank six inches.

  3. Disconnect the lower and upper pulleys and pull the starter out.  See the photo in paragraph A.1 below for the names of the parts of the starter.

  4. Relieve the tension on the rewind spring by pulling out about one foot of the starter cord while holding the pulley from turning.  Pull enough cord off the pulley until you reach the notch in the pulley.  Put the cord in the notch and gently let the pulley completely rewind with the cord in the notch.  Be sure to hold the pulley with a rag or your thumb so that it turns slowly.  It is under tension!  This way, the cord is not retracted but the pulley turns and the spring tension is relieved.  The cord and handle should remain attached to the pulley.

  5. Remove the center starter bolt.  Pull the pawl cover out.  Remove the two pawls and two springs.  The flash spring will exposed.

  6. Carefully pull up the pulley from the starter housing just enough to let the rewind spring start to pop out.  The rewind spring will go everywhere unless you restrain it some way.  Be ready for this.

  7. Thoroughly clean the rewind spring with mineral spirits to get every trace of grease off of it.

  8. Leave the Flash spring in the pulley.  It can be removed, however, but it is under great tension (see the next section).  I recommend leaving it in the pulley unless you have had experience working with very powerful springs.  Clean the Flash spring as best as you can.  A brush, mineral spirits, and air work the best.  Get as much of the grease out of it as possible.

  9. If the Flash spring must be removed, secure it to a solid surface, as here.  A bolt put through the pulley and held in a vise will securely hold it while working on the springs.  Failure to do this can result in serious injury if something gets loose.  The Flash side is facing up because I was about to remove the spring.  Use of pair of "needle-nosed" Vice-Grips to grab the inner tip of the spring.

    securing the Flash starter pulley


    safely holding a flash spring starter

    Here is another way to safely hold the flash spring in the pulley while installing or removing it.  If the outer end of the spring is firmly in the jaws of a vise, it won't go anywhere.  Thanks to Tom Bird for this tip.

    Polini Thor flash starter

  10. At this point, you can work on the starter assembly.  This can include attaching the Flash spring to the pulley, as in step #B1b below.


  1. Look carefully at #3a in the photo below in order to get the spring oriented correctly.  Start with the outside end of the spring and work the spring into the pulley.  The spring must be held at its outside circumference in order to keep it from popping out.

  2. After the springs are installed, use fine machine oil (e.g. air tool oil) to lubricate them.  MORE LUBRICANT IS NOT BETTER.  Do not use grease except a small amount around the surface of the inner shaft and on the inside of the bushing of the pulley.

  3. The threaded hole in the center of the starter housing center post must have all traces of oil and grease removed.  Use brake cleaner and air to do this and to clean the bolt, as well.  The bolt must be installed with threadlock.  If there is any trace of lubricant left on it or in the hole, the threadlock will not hold.

  4. There is a hole near the center of the pulley which is used to make sure the hook on the inner end of the rewind spring is properly installed in the slot adjacent to the inner shaft.  The slot can just be seen in #1 in the photo below.

  5. Wrap most of the cord in a counterclockwise direction when the rewind spring side of the pulley is facing up.

  6. Put the Flash pulley on the center shaft, making sure no grease gets in or on the threaded hole in the shaft.  A Q tip can be used to clean any grease away from the threaded hold.  Once the pulley is fully pushed down into place, it can be turned in a clockwise direction and the hook in the end of the spring guided into the slot adjacent to the shaft.  A small screwdriver can be used through the hole to push the hook into the slot, if necessary.

  7. Install the springs, the pawls, and the pawl cover in the pawl holder.  Turn the pawl cover as you push it down so that the pawls are correctly engaged in the slots of the pawl cover.  You can check things by turning the pulley in a clockwise direction to see if the pawls will push out to engage the starter ring on the flywheel.

  8. Apply blue threadlock to the bolt and install it.  Tighten to about 10 Nm.  Check again to be sure the pawls push out when the pulley is turned.  The pawl cover should not turn easily – which is the purpose of the circlip around its split shaft.

  9. Tension up the rewind spring the same way the tension was relieved.  The notch on the pulley allows the pulley to be turned (and the spring tensioned) without unwinding the cord (by pulling on it).  There should be enough tension so that the pulley will fully rewind against the friction created between the pawl cover and the center bolt.  If there is too much tension, there is the risk of pulling either of the spring fastening hooks out of the slots in the starter housing or pulley, respectively.  If there is too little tension, the starter handle may work loose and get in the propeller and make a huge mess!  One pilot has suggested that the starter pull handle be fastened with Velcro to the frame after starting so this cannot happen.

  10. Reinstall the starter on the engine.  All the screws should be torqued to 4-5 Nm except the top screw which should be just snug.  Threadlock must be used on all screws.  DO NOT USE THREADLOCK ON THE SCREWS HOLDING THE BACKPLATE TO THE ENGINE FRAME!  If you do, you may not be able to get the screws out of the screw holder that snaps into the frame.

  11. Just remember that no matter what you do, parts of the starter will wear out fairly quickly.  Read the details on this below.  The starters on these engines are FRAGILE so be gentle with them.

A. The problems

1. Flash mechanism

The Flash starter on the Thor 130 and other models has various problems and a short life because of design and material issues.  Rather than have a durable starter with few moving parts (Top 80, Simonini) Polini came up with a scheme that fails after a few dozen hours of engine operation.  It has little to do with whether the starter is even used.  The intent was to reduce the effort necessary to start the engine.  In this regard, the Flash is a success.  In fact, the Flash mechanism greatly reduces wear and tear on both the pilot and the starter mechanism, as a whole.  With some design changes, the Flash mechanism could be used and the starter also last much longer.

The Flash starter

Polini Thor Flash starter parts list

Starter mounting screws (not shown) – (3) 5mm x 80mm and (1) 5mm x 25mm.  However, the bottom 80mm screw should be replaced with a 90mm screws and locknut.

The failure of the Flash (including the standard) starter is primarily due to the extreme vibration that is created in lightweight 2 stroke engines.  Anything that can bend or move against some other surface will quickly wear or shake apart – unless it is protected in some way.

Why are starters on some other paramotors much more reliable and durable?  It is because as many moving parts as possible in the starter are attached to the flywheel so that they cannot move once the engine is running.  The extreme centrifugal forces of the rotating flywheel prevents the critical starter parts mounted to the flywheel from moving, rubbing, and wearing out.  The Miniplane Top 80 is an example of this design.  This starter will last the life of the engine.  The Top 80 starter housing and pulley that are attached to the engine housing has only one moving part (other than the spring) which rarely wears out.

The Flash starter has three issues:

  1. Rapid wear of the pawl holder [#4], the pawls [#7], and the pawl cover [#5].  The standard starter also experiences rapid wear of the pawl holder and its associated parts.
  2. Bunching up of the white anti-friction band that helps the Flash spring move smoothly.
  3. Movement of the Flash spring away from and out of the Flash pulley (As of February 2017, Polini has fixed this problem in new starters.)

The moment the engine is running, the starter begins to fail:

  1. The Flash spring begins its movement out of the Flash pulley towards the pawl holder.  This has been fixed on the newer models.
  2. The white tape bunches up and begins to interfere with the operation of the Flash spring as well as helping it push up on the pawl holder.  Newer versions of the flash spring do not have the tape.
  3. As the pawl holder is forced against the pawl cover, the pawls jam and are prevented from engaging the starter ring on the flywheel.  This is largely cured on the newer models, thankfully. 
  4. As the engine continues to run, the pawl holder wears badly where the pawls contact it, the pins break off, and pawls fail, and the pawl cover looses all of its grooves and ridges that direct the pawls.  It appears that newer versions of these parts are better hardened and have less tendency to wear out so quikcly.

After more engine time, the pawls will become free of the holder and cover.  They then get sucked into the cooling fan, wrecking everything.  I launched one time and a minute later I heard this awful noise.  I landed immediately and saw what had happened.  It was a mess that kept me on the ground for days.  Even though the newer versions of the flash are less flimsy, pilots must keep their eyes on things, just the same.

The Flash starter (original, old style) in the photo below has less than 10 hours of engine time.  The end hook on the Flash spring has already begun moving out of the Flash pulley – jamming the pawl holder into the cover.  The white anti-friction band that is in the flash spring is bunching up and out.  It, too, will eventually jam up against the pawl holder forcing it into the pawl cover.

Polini Thor flash starter problem

Thor 130 flash starter failure

Below, wear points on the pawl holder from the vibration of the pawls while the engine is running.  The pawls have started to wear into the holder (red arrows).  The yellow arrows point to the pins, now broken off, that held the pawls in place.

Polini Thor Flash starter

Below, the red arrows point to deep grooves cut in the pawl cover by the vibrating pawls.  The presence of much grease only slightly slowed down the damage.  The yellow arrows point to worn down rims of the pawl cover that aligns the pawls correctly.  As a result, the pawls would not engage the starter ring on the flywheel and the unfortunate pilot could not start the engine.  He had to pack up and go home.

Polini Thor Flash starter

The tang that advances the pawls into the starter ring when the starter is first pulled has been worn away.  When these tangs wear away, the pawls will not be retracted when the starter rope is released.  They will then hit the starter ring and the tips will grind away, quickly making the starter useless.

Polini Thor Flash starter 

2. Weak mounting structure

Pilots in the normal course of starting the engine may also pull the lower starter housing mounting bolt right out.  Sometimes, the bolt will shear at the threaded end, as on the right.  As of 2018, this problem still exists.

Polini Thor flash starter mounting bolts that failed

The mounting points for the Flash starter.  The top mounting point can twist in the plastic cooling housing and make the screw difficult to remove.

Polini flash starter points of failure on the engine shroud

Below is a photo of the Polini Flash starter mount reinforcement.  It helps prevent the movement of the starter when it is pulled – and the stripping/shearing of the existing bolts and mounting points.  However, it does nothing to prevent the disintegration of the starter itself.  This part is not available in the Western Hemisphere at this time.  If the lower mounting screw is replaced with our special screw and locknut, the starter should not come loose as easily.  So far, the starters on our engines have held steady without the addition of this reinforcing plate.  But this is the least of the problems with the Polini starter.

Polini flash starter mount reinforcement

3. Starter cord

The OEM starter cord wears out quickly.

4. Pulley failure

I do not know if other frame manufacturers use the same pulley brand (Viadana) as Miniplane does.  This pulley is of poor quality.  The starter cord can easily cut into the rotating part of the pulley if the bearings seize.  They are guaranteed to fail after a short period.

Below is a photo of the OEM pulley that was destroyed by the starter cord on a Thor 130.  The plastic ball bearings seized, preventing the pulley from turning.  The movement of the cord around the pulley quickly cut a groove in it.  This pulley was not designed for the load.

Miniplane starter pulley showing how the cord can destroy it

Replacing a failed OEM pulley with another OEM pulley is useless as it will just fail again.

B. Fixes for these problems

1. Flash starter fix

Pilots can replace the Flash mechanism or modify it.  I recommend keeping the Flash but it must be modified.

a. Replacing the Flash mechanism

Option 1 Install standard starter   (Note: This is not the best option.)  If you are not handy with tools, you can replace the Flash starter with the non-flash standard starter.  It is easy to do but it is the most costly solution.  A downside is that you will no longer have the easy starting of the Flash which is important for all clutched engines.

Option 2 Install non-flash insert  (Note: This is not the best option for the newer versions of the flash system.)  We have developed and manufactured a solid machined aluminum insert to replace the Flash spring and pawl holder.  It is easy to install.  The main advantage of the insert is that it eliminates the problem of the Flash spring moving out of the Flash pulley and jamming against the pawl holder.  Another advantage of the insert is that it has steel roll pins rather than the flimsy plastic pins as are in the OEM pawl holder.  However, the use of the insert (which eliminates the Flash mechanism) means that more strength is needed to start the engine.  Many pilots will have to place the motor on their backs and start it with both hands.

The aluminum insert kit is available from Miniplane-USA (it is listed at the bottom of the web page).  The kit includes the machined insert and also a replacement bolt of better quality with a locknut.  Please be sure to follow these instructions for installing the Flash starter insert.  Southwest Airsports can install the kit for a nominal charge.  Contact us for more information.

Even though the insert is metallic, it will still wear some due to engine vibration.  Note the dimples (red arrows) caused by the plastic pawls.  The pawls from the insert were completely worn out due to vibration of the engine.

Polini Thor Flash starter insert

Summary   I recommend that you install the complete standard starter or the aluminum insert ONLY if you are unable to do the modification given in section b. below.  If you can do the work in b., you can keep the Flash mechanism, which is the best option.

Whatever option you choose, learn how to properly start your engine.  We have developed this technique that allows any engine with a horizontal diaphragm type carburetor to be started the first pull, every time.  No choke is used nor is it necessary.  It works when the engine is hot or cold.  It will not flood the engine.


The aluminum insert.  Note the black steel roll pins.  They will not break or wear out, like the plastic pins in all of the OEM starters.

replacement for the Polini flash start mechanism 

b.) Modifying the Flash pulley and spring

This modification is a better option than replacing the Flash mechanism with the non-Flash standard starter.  Note: If you have the newer versions of the flash system, these modifications have already been done at the factory.  The pulley and the flash spring are joined together so that the spring does not work its way out, eliminating the need for replacing it.  Here are the steps:

Southwest Airsports can make this important modification, if needed.  All we need is the intact starter.  Contact us for more info.

Here is the modified Flash pulley and Flash spring with the screw holding everything tight.

Polini Thor modified Flash starter spring

Pilot Larry Koral sent me these photos of some new Flash starters from Polini with the flash spring secured (as of January 31, 2017).  They added a small raised plastic extension for a screw and washer.  However, I do not think such a small screw can successfully resist the lateral pressure from the spring.  Our fix for this would require the screw to be sheared off – something that would not happen.  Everything in the starter is subject to extreme vibration.  Will it hold fast?  Pilots can always do the modification detailed on this page if this fix from Polini fails.

As of 2018, Polini has added a second screw to hold the flash spring in place.

new Polini flash starter modification

new Polini Thor flash starter modification

c.) Premature wear of the pawls, the pawl holder, and cover

There is no solution to prevent these parts from quickly wearing out but as of late 2018, the quality of the material used to make the pawl assembly has improved.  I suggest that pilots use only the smallest amount of grease – it just gums up everything and makes a sticky mess that must be cleaned up next time.

We stock a kit that includes the pawl holder and all of its internal parts for $15 (price subject to change) + shipping.  Contact us to order.  These parts should be considered consumable items, like the spark plug.  We hope Polini will do a major re-design of the starter so that it does not wear out so quickly and more resembles the Top 80.

If modification [b.] above is done, pilots will only have to remove the starter from the engine, undo the center starter screw, and install the pawl holder kit from step [c.]  The engine will be good to go for another 25-50 hours.  How do you know when to replace the parts?  The starter will no longer work....  It is a good idea to keep an extra kit around.  Remember that you are wasting your time if you do not secure the Flash spring in step [b.] above.

Make certain that the center threaded hole in the starter is absolutely clean of oil/grease by using brake cleaner and air.  If there is but a trace of grease/oil on the screw or in the hole, the threadlock will not hold.  Here is what happens if you are not careful to clean things.  You will be flying along and your engine will make a horrible noise as the cooling fan eats up starter parts....  It will continue to run but there will be no cooling and the engine will quickly overheat.

2. Improving the weak mounting structure

The most important modification is replacing the lower starter mounting bolt with a longer, higher quality bolt and locknut.  This is included in the insert kit from Miniplane-USA.  If the insert kit is not used, we can supply the special screw for replacing the OEM screw located at the bottom of the starter and a locknut.  Contact us.

3. Heavy duty starter cord

Use a Dyneema cord.  It lasts forever and is designed for this sort of use.  It is available from Miniplane-USA.  Scroll down to "Top 80 Starter Cord, Dyneema 1.25m".  It will also work in other Polini Thor engines.  However, be sure to cut the new cord to the exact length of the cord in your starter.  Having too long a cord can result in the main spring being yanked out of its anchors.

4. Better pulley

Pilots annoyed with the poor quality pulley from Miniplane can purchase the Harken 082 Single Bullet Block for about the same price and replace both the upper and lower pulleys.  The best price is from APS (< $15).Harken 082 single bullet block  However, if you use the Harken 082 for the lower pulley, it is not as easy to remove as the Viadana because the Harken does not have a shackle.  You will have to unscrew the anchor to disconnect the starter system from the frame.  This is a small inconvenience compared to the expensive (2X) Harken equivalent to the lower Viadana pulley, the Harken 166 Bullet Block Single with Swivel (< $26 at APS)  The Harken pulleys are particularly designed for high loads (136 kg/330 lb) and rough use.  They will NOT fall apart like the Viadana pulleys.    Harken 166 bullet block single with swivel




The Harken pulley (block) should never wear out.  If you purchase the OEM, it WILL wear out quickly.

The Polini Thor engines are among the quietest and smoothest running of all paramotors.  That is why we created these pages to help improve them.