Specifications for the Polini Thor models

Most troubleshooting, assembly, & tips are the same as with the Top 80


Carburetor – The Thor 100 and 130 use the WG-8.  The Thor 190 and 200 use the WB-37. The Thor 250 uses the Polini carburetor.

Compression, engine – 130-150 psi, depending on altitude.  This is what you can expect for a new engine.  Used will be less.

Cylinder base gasket – thickness 0.5mm, install gasket with the lettering facing down.  Never use sealant on engine gaskets.  It is unnecessary (manifold gaskets are the only exception)

Cylinder head gasket – install with the ridge on the gasket UP

Cylinder Head Temperature Maximum 230°-250°C  This may be increased to 265°C-280°C for brief periods.  These values are from the Polini User Manual which seem high.  We use the TTO brand of gauges which register a lower average maximum running temperature than the Polini values.  Under full load, I have rarely seen the temperature exceed 180°C.  In any case I would not run the engine above 200°C using the TTO CHT.

Flash starter

Fuel filter Info – Use a 10 micron inline filter.  We stock a commercial chainsaw filter.  Contact us to order.  Miniplane-USA has the OEM filter.

Fuel line/tubing size – Use Tygon® LP1100 Low Permeation Fuel Tubing (ethanol resistant).  It is available from Miniplane-USA.  Do NOT use ordinary vinyl tubing as it will become stiff quickly and stress the connections on the tank and engine.  Auto parts stores do NOT have the right type.

Fuel pump vacuum – 5" Hg (dry) 7" Hg (wet w/ fuel)

Fuel Info – Note: The Polini manual specifies that pilots use unleaded fuel (the only kind available to pilots in the EU).  We contacted Polini and they specifically stated in writing (available on request) that pilots may use AVGAS in any of their engines.  AVGAS is preferred over gasoline containing ethanol.

Ignition, coil – The official Polini user manual states that the spark plug boot terminal to ground is 5K Ohms but a new Thor 130 measured 9K Ohms which means that the secondary wire is a carbon-core ignition noise suppressing type i.e. some Thor models may have different values.

Ignition coil primary resistance (all models except the 190) – 1K+ Ohms (blue wire to engine ground).  The coil has electronics in it which makes this value difficult to measure so any value greater than 1K Ohms is OK.  If you get no value switch the Ohmmeter leads.

Ignition coil secondary resistance – 9K Ohms ±10% (spark plug terminal to engine ground)  Can be 5K Ohms on newer models.

Ignition magneto coil resistance – 290 Ohms

Mounts, engine – 30mmL x 30mmW x 8mm (stud x socket) There are (4) mounts, total

Muffler spring removal – Use paraglider line to stretch the springs for replacement/removal.  Do NOT use pliers to stretch the springs because this will nick the tempered surface of the spring and weaken it.  Here is a video on how to properly do it

Power output

Propeller shaft, seal – 26 x 36 x 7 mm

Redrive oil – Here is a list of the correct oils that may be used in the Thor redrive.

Reed valve – if the petals get weak, chip, or break into pieces the engine will not achieve full power or may not run or start.

Spark plug (other than the Thor 250) – NGK BR10EG, gap 0.9mm (0.035")  This is a resistor type spark plug.  Pilots may also use the B10EG/ES or B9EG/ES.  Use of a non-resistor plug will only increase the amount of noise created by the ignition that may be picked up by a two-way radio.  BE SURE TO PUT RED THREADLOCK ON THE PLUG TERMINAL OR IT WILL LOOSEN AND SELF DESTRUCT!

Spark plug Thor 250 – see the Thor 250 page

Special tools for the Thor engines.  These include the special pullers used to disassemble the engine.

Starter cord – 1.8m (6') When cord is fully installed, wind the spool 3X to ensure adequate tension on the cord which keeps the pulley out of the propeller.

Starter cord pulleys – Harken 082 (superior to the OEM Viadana)

Starter mounting screws – (3) 5mm x 80mm and (1) mm x 25mm.  However, the bottom 80mm screw should be replaced with a 90mm screw and locknut.

Torque Values

Note: The Italian paramotor manufacturers continue to use button-head screws on their engines, regardless whether they are needed or not.  Button-head screws have soft heads which make them very easy to strip with a hex bit when attempting to remove them.  Replace them with hex-head or socket-head screws, as necessary.  Go figure....

Torque conversion chart (Nm to inch pounds) Here is an online conversion program from Nm to ft-lbs or the reverse.

Torque values – The link is to the Top 80 specification page.  If you do not see the particular screw, bolt, or nut below, use the general values in this table:

Threadlock – read this important page on threadlock and how to use it and when NOT to use it.

Carburetor screws 6mm – 8 Nm

Crankcase screws 6mm – 8 Nm

Crankshaft nut, clutch side – 60 Nm

Crankshaft nut, starter side – 40 Nm

Cylinder head nuts

Engine to frame button head screws 8mm – 10 Nm – use Blue threadlock

Exhaust stud nuts 6mm – 10 Nm – use RED threadlock.

Magneto bolts – 9 Nm

Muffler button head screws 8mm – 10 Nm – use BLUE threadlock

Propeller central screw – 40 Nm – use BLUE threadlock

Reed valve screws – 8 Nm


Starter mounting screws – 2-3 Nm  It is easy to over-torque these screws.  Threadlock is not generally necessary on these screws.  Do NOT put threadlock on the top screw!

Maintenance intervals

General instructions

Changing the redrive oil and the spark plug are the (2) most important maintenance items that must be done.  Use a Sharpie to write reminders on the top of the redrive (or other semi-flat area).  Any other method will not be as effective.  The markings are easily removed with brake cleaner or mineral spirits.  This way, you won't forget!  You have an hour meter/tachometer installed right?

writing reminders on the Top 80 redrive

A. REDRIVE SERVICING  It is very important to change the redrive oil on schedule because it gets quickly contaminated with clutch material.  If your clutch oil appears really black when you change it, increase the change frequency.  Note that the redrive will use oil because of slight leaks out of the relief valve.

B. Below are service items that are particular for the Polini.  Pilots would do well to carefully study the servicing intervals for the Top 80 which I have developed to ensure long engine life for any 2 stroke aviation engine.  The carburetor and fuel system are the most common items that must have regular service.  Failure to regularly service the carburetor can result in permanent engine damage.  It is advisable to measure the engine compression when it is new and use this value as a reference point.

C. The Polini Thor Flash starter is a disaster.  See the Flash starter page for more information and (2) good, permanent fixes – and one of the fixes costs just $16.

First 10 hours

Every year (minimum)

Every 15 hours – change spark plug if AVGAS must be used

Every 25 hours

Every 50 hours

Every 100 hours – this is an important and extensive service of the engine.  Everything may be fine for 150 hours but then maybe not....

Every 200 hours

Every 400 hours

Turkey Vulture