Polini Thor information for the common models
updated January 22, 2021
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The Thor models share a common design and many parts. If you cannot find the info you need below or on the individual Thor model pages, check the Top 80 section for a wealth of info that is common to all Italian paramotors.
SPECIFICATIONS – Dimensions, torque values, maintenance intervals, and other useful information
General assembly instructions - It is CRITICAL when assembling Thor engines that the manifold mounting nuts be properly torqued using blue threadlock if you do not want any leaks.
Airbox support problems – The airbox tends to slip crossways onto the carburetor and leak after the engine is run for some hours. Here's the fix.
Assembly video – This is for the Thor 130, other models similar.
Battery – WARNING! Polini specifically forbids the use of lithium ion batteries in the electric start system
Bearing condition – What condition are the bearings in my engine? Which one is the most likely to fail first?
Bearing replacement and crankcase disassembly/assembly – Here is how to replace the main crankshaft bearings and seals
Carburetor – The Thor 100 and 130 use the WG-8. The Thor 190 and 200 use the WB-37. If your engine is not purring like a kitten in the mid-range, you need to perform the midrange modification on your carburetor. The FSM will permanently fix the midrange problems but it is still in the testing phase. The Thor 250 has a custom Polini carburetor.
Carburetor preheat system – see "Cold weather operations" below
Crankcase assembly/disassembly – see "Bearing replacement and crankcase assembly/disassembly" above
Crankshaft replacement – see "Rebuilding a paramotor" below. The paramotor must be completely disassembled.
Choke control – This is needed for safety and convenience.
Clutch – Information and servicing procedures.
Clutch Oil – Here is a list of the oils that can be safely used in the Thor redrive.
Cold weather operations – Unfortunately, the WG-8 and the WB-37 are sensitive to both high altitude and/or cold weather operations.
Coil secondary wire replacement – This is one of the most common points of failure in ignition systems.
Compression relief valve – NEW Southwest Airsports now has a compression relief kit that does away with the quirky Flash mechanisms and the need for powerful electric starters to get clutched engines past TDC so they will start.
Crankcase replacement – see "Rebuilding a paramotor" below. The paramotor must be completely disassembled.
Cylinder head & piston notes – when doing the 100 hour required maintenance
Cylinder head, temperature, maximum – 230°C and 250°C maximum running temperature, never exceed 265°C/280°C but only for a few seconds.
Cylinder head temperature gauge – Not having a CHT is like driving a car without any gauges or warning lights. Most of the time you don't need them....
De-carbonizing a two stroke engine – Alex Varv shows how to do it without removing the cylinder. However, I do not recommend using any sealant between the cylinder and cylinder head. I have never had a head leak when the "O" ring is new and installed properly. The exhaust port should also be cleaned at the same time.
Decompression port check – Here is an easy, simple way to check whether the port is clogged or not.
Decompression port cleaning – It must be clear. Failure to keep it free of combustion deposits will greatly shorten the life of the starter.
Drips – Two stroke engine carburetors drip/leak fuel by design. It cannot be helped.
Electrical troubleshooting – see "Ignition troubleshooting" below
Engine leaks – see "Leaks of the engine, exhaust, and redrive" below
Engine stall – see "Stall" below
Exhaust flange springs – Use paraglider line to stretch the springs for replacement/removal. Do not use Vise-Grips or 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. A defective exhaust flange gasket cannot be fixed with RTV – replace the gasket. Use PG line (best) or aircraft wire to secure the springs if they break.
Exhaust gasket installation – The side of the gasket with the greater metal-faced area goes away from the cylinder head. Thoroughly clean and degrease all surfaces, apply a thin coat of gray RTV to both sides of the gasket, and install the exhaust port. Apply RED threadlock to the studs and torque to 10 Nm. Wait (10) minutes and re-torque. Finger tighten the nuts until RTV squeezes out from the flange, wait an hour, and then tighten to torque.
Exhaust port cleaning – after many hours the inside of the exhaust port and the manifold can have substantial deposits of carbon and/or lead phosphate/monoxide.
Exhaust system installation – 1. Install springs first per above. 2. Install the button-head screw underneath the carburetor first THEN 3. Install the button-head screw underneath the exhaust port. Use blue threadlock on screws and tighten 3-4 Nm (just snug, let the threadlock do its job).
Flash starter – an expensive, annoying disaster NEVER PULL A POLINI STARTER WHILE THE ENGINE IS RUNNING! IT WILL CHEW UP THE PAWLS!
Flash starter cord length – see "Starter replacement cord" below
Flash starter parts list – before 2019
Flash starter parts list – after 2019
Flywheel removal and installation – this information is from the relevant section of the timing page
Frame cracks – see "Metal fatigue" below
Fuel filter – What kind/type to use? If you choose poorly, the engine will also run poorly, if at all. Removal and installation tips. The fuel system MUST be purged of old fuel and air when changing out the fuel filter!
Fuel line size/installation – these are IMPORTANT notes that will prevent engine fuel starvation
Fuel system modification – the FSM dramatically fixes fuel starvation and most performance issues (still in the test phase)
Fuel system test – A more thorough test of the fuel system
Fuel tubing size – ID 4.8mm (3/16") x OD 8mm (5/16") 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.
Ignition coil – the black wire goes to ground, the blue wire goes to the kill switch and magneto
Ignition timing – The Thor engines have the ignition timing fixed and it cannot be changed.
Ignition troubleshooting – the Thor engines have magnetos and have some special techniques that must be used to troubleshoot them
Kill system, alternate – The Italians have demonstrated poor quality control over the years, including faulty cabling and connectors in the kill switch system installed on paramotors. This could be exceedingly dangerous with any engine, especially the Minari 180/200.
Kill switch problems – A low bidder made the wire used in the kill switch circuit.
Magneto – see "Ignition troubleshooting" above
Metal fatigue – Pilots who put 100's of hours on any paramotor must keep an eye out for this hazardous and hard to see problem.
Midrange roughness & "four cycling" – see "Performance tuning" below
Miniplane frame information – options, sizes, side stick lengths, etc.
Mounts, rubber* – Here is a way to quickly check them. If you replace them with the heavy duty Viking mounts, do not make the mistake noted here.
Overhaul – see "Rebuilding a paramotor" below
Owners manuals – see the links for each particular Thor model on the main paramotor page
Performance Issues, general – This is what to do if the engine will not start or, for example, dies at full throttle
Performance tuning – Most paramotors run poorly in the midrange, the range that we spend most of our time flying in.
Piston failure – Madsen's (a chainsaw dealer) gives the various ways a piston gets destroyed with some info on the causes. Paramotors are more like chainsaws than any other engine. In fact, paramotors use carburetors from obsolete chainsaw engines.
preheat system of air entering the carburetor – see "Cold weather operations" below
Propeller hub info, removal, & installation – this page is particularly about the Top 80 but has important information relevant to the all hubs, especially vibration sources.
Propeller info – General information including how to correctly attach and repair it
Pulleys – see "Starter pulleys" below
Purging the system of fuel – It must be done if a paramotor is to be stored for more than a few weeks, especially if you are using ethanol fuels.
Rebuilding a paramotor – includes disassembly and assembly of the major parts of the engine e.g. flywheel, cooling fan, carburetor, etc.
Redrive fill plug gasket – this flimsy gasket fails after no time. An 11mm ID O ring will work better than the gasket ever did. Do NOT over-tighten.
Redrive gear noise – it can be safely ignored. The noise will be more pronounced when the prop is rotated in one direction vs. the other.
Redrive repair – see the clutch redrive section of Rebuilding a paramotor
RTV – e.g. Permatex Blue or Ultra Grey. Used to seal case halves, some gaskets, and surfaces. Apply with a clean finger. Forget the spout that comes with the tube. It is useless. Use Ultra Grey for sealing surfaces that may become hot, like the exhaust flange gasket. MORE SEALANT IS NOT BETTER! It is NOT as simple as most think!
Safety net installation – on NEW Miniplanes the safety net comes already assembled and ready to install
Safety net replacement – replacement safety netting from Miniplane must be assembled. Here is help to prepare the net for installation (above).
Safety net wear – How to minimize wear and tear on the safety net
Spark plug installation and information – do NOT waste time troubleshooting an engine unless the spark plug is new, correctly gapped, and installed. IS NOT SIMPLE!
SPECIFICATIONS – Dimensions, torque values, maintenance intervals, and other useful information
Springs, exhaust – see "Exhaust springs" above
Squish – Polini does not require the squish to be adjusted on their engines. Go to this page for information about squish and what it is.
Stall – Going to full throttle, the engine stalls! What happened?
Starter – see "Flash Starter" above
Starter cord length – see "Starter replacement cord" below
Starter pulleys – The OEM Viadana pulleys will quickly wear out and fail. Here is the solution...
Starter replacement cord – The strongest and longest lasting you can install on your engine.
Starting – Start your engine the first pull, every time
Support Bracket – Polini has modified the engine support bracket for safety reasons
Stress cracking of engine components – see "Mounts, rubber" above
Temperature – see "Cylinder head, temperature, maximum" above
Throttle placement in the hand while launching a paramotor
Throttle cable – Cleaning, lubrication, modifications, and cruise control info.
Timing – see "Ignition timing check" above
Torque Values – See "SPECIFICATIONS" above. The specific Thor manuals on this website also have torque values. If you cannot find the correct value, check the the Top 80 specification page.
Users manuals – see "Owners manuals" above
Vibration – see "Propeller hub info, removal, & installation" above
Warming up – when is a paramotor warmed up sufficiently and ready to fly? When the cylinder head temperature reaches 70-80ºC, the fuel/air mixture is sufficiently hot enough to ensure that it is 100% vaporized and that the engine will not be fuel starved and potentially overheat. Overheating can happen very quickly!