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SOUTHWEST AIRSPORTS

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Polini Flash starter problems & fixes

by Had Robinson

Important update

23 May 2017 --  The best options for improving the Flash mechanism are listed in steps B1b and B1c below.  Steps B3 and B4 should also be done.  I am looking at other starters and seeing how difficult it would be to mount them on the Thor and Minari engines.

Maintenance notes  Use nitrile gloves to handle things.  Working with springs can be dangerous!  Wear eye protection.  When assembling the starter, only put a small amount of grease on the starter housing center post.  Springs should have all traces of grease removed and fine machine oil (air tool oil) used instead.  Secure the flash pulley in a vise or use some HD screws with washers through the spaces near the outside of the pulley to firmly attach it to some surface.  Failure to secure the pulley can result in serious injury!  Carefully remove the rewind and flash springs by pulling the center end of the spring out little by little while using your thumb/hand to prevent the entire spring from popping out.  Once the springs are removed you can clean them thoroughly.  Installation is the reverse.  Start with the outside end of the spring and work it in the pulley moving towards the center.  After the springs are installed, use fine machine oil to thoroughly lubricate them.  Do NOT use grease.  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 and if there is any traces of lubricant left on it or in the hole, the threadlock will not hold.  Just remember that no matter what you do, parts of the starter will wear out fairly quickly.  Read the details on this below.

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 an outstanding 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 last much longer.

The Flash starter

Polini Thor Flash starter parts list 

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 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 -- and wearing out.  The Miniplane Top 80 is an example of this design.  This starter 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 wear 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.
  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.
  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. 
  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.

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.

The Flash starter 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.

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 bolt is replaced with our special bolt 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 and lacks sufficient breaking strength.

4. Pulley failure

I do not know if other frame manufacturers use the same 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:

a. Replacing the Flash mechanism

Option 1  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.

Option 2  Pilots who are handy can replace the Flash pulley (#3) with the standard pulley.  It is now available in the U. S. and we stock it.  It costs a fraction of a new starter and much less than the aluminum insert.  However, it will not last as long as the aluminum insert.  The pins that support the pawls are plastic and quickly break.  Pilots must have modest mechanical skills to trade out the springs and parts of the Flash with the standard starter.

Option 3  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.

Polini Thor Flash starter insert

Summary   I recommend that you install the complete standard starter, the standard pulley, or the aluminum insert 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.

Warning  THE POLINI STARTER -- EVEN WITH THE MODIFICATION -- IS DELICATE.  DO NOT YANK REPEATEDLY ON THE STARTER!  THIS WILL WEAR IT OUT QUICKLY.  THE STARTER MUST BE CAREFULLY MONITORED AND MAINTAINED -- SEE THE THOR SPECIFICATIONS SECTION FOR MORE INFO.

The standard starter pulley

Polini Thor stadarnd starter pulley

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.  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.  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.  There does not appear to be any improvement in the overall design of the starter pawl assembly.  I am still trying to figure out how Polini missed all of this?  Did they ever test these starters more than a few minutes?  One wonders....  Great engines, otherwise.

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.  Do not use 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.

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 bolt and 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.

4. Better pulley

Pilots fed up with the poor quality pulley from Miniplane can purchase the Harken 082 Single Bullet Block to replace the upper pulley.Harken 082 single bullet block  The lower pulley has a swivel and is equivalent to the Harken 166 Bullet Block Single with SwivelHarken 166 bullet block single with swivel

 

 

 

These pulleys have a (5) year warranty.  They are about twice the cost of the OEM but will never wear out.

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.

vulture