paragliding training center
by Had Robinson
December 2018 – French ultralight pilot, Catalin Atodiresei, has developed a clever way to adapt the superior Miniplane Top80 starter design to the Thor engines. See paragraph B(1)d below for more info.
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 could also last much longer.
The Flash starter
arter 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 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:
The moment the engine is running, the starter begins to fail:
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.
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.
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.
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.
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.
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.
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.
The OEM starter cord wears out quickly.
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.
Replacing a failed OEM pulley with another OEM pulley is useless as it will just fail again.
Pilots can replace the Flash mechanism or modify it. I recommend keeping the Flash but it must be modified.
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.
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.
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 ON MAINTAINING THE STARTER.
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.
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.
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.
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 apparently 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.
An ultralight pilot in France, Catalin Atodiresei, has adapted the durable and simple design of the Top 80 to the Polini Thor starting system. It is somewhat technical to do but he has offered to help pilots with some of the more difficult aspects of this complete redesign of the Thor starter. I was hoping someone in the world would do this and Catalin has generously done the work and stepped forward helping all those who love the quiet and otherwise reliable Thor engine. His modification was for the Thor 100 but can easily be used on other Thor engines that utilize the Flash starter.
Please navigate to this page for the details on adapting the Top 80 starter design to the Thor engines.
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.
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.
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). 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.
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.