At Rotax Rick’s Engines, we build the finest two-stroke custom improved engine that money can buy. While we guarantee our work, YOUR life depends on the engine and you should be very diligent in installing and operating your new engine.
Proper Cooling System
- Your expansion tank OR Radiator must be mounted above the cylinder head.
- The amount of airspace in the expansion tank or radiator MUST be large enough to have 1 inch of coolant in it when the engine is cold and 1 inch below the radiator cap when the engine is at its maximum temperature.
- No overflow bottle is needed if the above steps are taken, but we do recommend one regardless.
- I recommend in a plugs up installation that the steam vent line (the line from the head to the expansion tank or radiator) be clear. Use a 3/16 ID and 5/16 OD hose.
- Using this hose you now have a site gauge to see the coolant level. At the coldest temperature it should have at least 1 inch of coolant above the cylinder head and at its maximum 1 inch below the radiator cap. (this is a great way to pre-flight at a glance).
- THIS IS WHERE MANY PEOPLE CAN GET IT WRONG! The expansion tank or radiator inlet must come off the constant pressure cylinder head fitting side, not the sucking water pump side.
- The coolant then comes from the cylinder head to the expansion tank or radiator (by its cap), or from the expansion tank to the lower fitting on the radiator (if it has a lower fitting).
- The water comes TO the engine, out of the radiator to the water pump inlet side (below the exhaust Y pipe).
The reason the expansion tank or a high mounted radiator can not have the radiator cap on the inlet side is it will pull the small seal in the radiator cap and suck air. This can cause a major water pump failure. The hose into the engine was super hot while the outlet hose was cold. It would be like drilling a hole in the hose that runs to the water pump.
That being said, on inverted engines DO NOT use a barb fitting on the water pump inlet cover. Just remove the bolt to fill the system. Once coolant is coming out of that hole, the system to that point has no air in it. Normally that hose runs up to an expansion tank near its top. That hose has a suction on it 100% of the time. If it’s exposed to air it WILL SUCK AIR.
Here are some things to consider when you are installing your 670 engine in an aircraft:
- Because the 670 can demand upwards of 11 gallons per hour (gph) at full throttle, there may be times when Rotax’s standard pulse fuel pump (which is rated at 9 gph) cannot keep up. This is dangerous, because you are running the engine out of gas and oil, and after 15 seconds this can destroy the engine. We require that you install an electric fuel pump (e.g. the Facet Cube Style 12 Volt Fuel Pump, 3-4.5 maximum PSI). Install parallel to the pulse pump. This will give you a redundant fuel supply as well as dual ignition.
- Use fuel filters in your system to maintain the cleanest fuel flow possible. We recommend one at each fuel tank exit and one in each line from the pulse pump to each carburetor. Use only Stainless Steel screen type fuel filters.
- Use Stainless steel fuel filters at the fuel tank outlet and one in each of the lines from the pulse pump to the carburetors. You do not need an overflow bottle. For radiators mounted below the engine you need a expansion tank large enough so when the engine is cold you have coolant at least 1 inch above the highest part of the cylinder head. When at max temp one inch below the radiator cap. The system does not have to be pressurized. If you use a overflow bottle and it lets the vacuum in the cooling system overfill the system, then your radiator cap must work perfectly. As it heats up and expands the radiator cap must release the excess pressure. Lets say you have an 18 lb. cap, but it takes 40 lbs. to open it, you’re very likely to blow a head o-ring or the base gasket. Fill a pressure cooker and seal it. Put it on the stove, and the pressure is going to come out one way or the other. Same thing here.
- Check the torque on the head bolts before the first start up and after 2 hours of operation. 250 inch lbs is the desired torque. This is only required on air-cooled engines.
- Be sure to check the static RPM of this engine on your aircraft. 6250 – 6350 RPM is what you want with a 670, 503 or 582. I like to start at 6400 rpm and then adjust. If you want a cruise setting, then set the rpm at 6500 flat out straight and level. For a climb setting, set it for 6800 rpm straight and level. For maximum power on a real short strip, set the static RPM at 6700. You will need to add pitch to your propeller blades if you are stepping up to the 670. Be sure to safety wire as necessary.
- If you do not have one, we recommend a coolant expansion tank and overflow bottle as part of the cooling system. The coolant expansion tank will be located at the highest point above the engine. You can use the Rotax factory tank (nice but $150, or a Skidoo 583 or 670 expansion tank). Run a 3/16 ID 5/16 OD clear steam vent hose to use as a site gauge on pre-flight. When the engine is cold, the fluid level should be at least 1 inch above the cylinder head. At maximum temperature, the fluid should be 1 inch below the radiator cap. This coolant system should not ever be under pressure.
- Filling coolant after an engine PLUGS UP installation: remove the radiator cap; fill until full. Use green antifreeze in your engine; cover the opening where the radiator cap goes with your hand; blow in the overflow tube; repeat this until water comes out of the cylinder head water temp probe hole; install the water temperature probe; top off; run the engine and shut down. Inspect the level and top off one more time in case of an air pocket.
- Filling coolant after an engine PLUGS DOWN installation: remove the plug in the water pump inlet cover; fill with coolant until water comes out of the water pump inlet cover; install the water pump cover plug; continue to fill until completely full; remove the expansion or radiator outlet fitting that runs to the radiator; cover that hole in the radiator or expansion tank with a helper’s hand. Leave the hose that installs there open; with your hand, cover the spot where the radiator cap goes and blow in the over flow tube; repeat this until coolant comes out of the hose that is disconnected; reinstall that hose and top off the expansion tank; run the engine and shut down. Inspect the level and top off one more time in case of an air pocket
- Be sure to WATCH the water temperature on a new engine at start up, and before flight.
- Since this is a new engine, possibly with a new gear box, be sure to check the oil in the gear box and the rotator valve system before starting the engine. Safety wire appropriate parts when you are finished.
- Ground your engine to the battery and the frame of the plane.
- You may have ordered our tuned exhaust system with a bracket specific for your aircraft. You may find that some modification of the bracket is in order during installation. Safety wire the exhaust system springs when finished.
Be gentle on the engine for the first five hours. Help the pistons and cylinders seat themselves properly. Break-in your engine for a minimum of five hours, plus observe our recommended start up procedures each time. The most important thing to avoid is full throttle for the first 5 hours and preferably for the life of the engine. BUT the first 5 hours is where cross hatching in the cylinders can be scrubbed off and potentially cause reduced piston and ring life. REMEMBER THIS: In 90% of the engines that fail, the damage that caused the failure happened when the engine was running at full throttle. IF YOU DON’T NEED IT DON’T USE IT!
- Use premium gas. Use E-10 or non E-10 gasoline. FRESH is the most important thing. Rotax has a warning out not to use Non-ethanol gas. WHY? The big Seadoos are filling up at marinas with non-ethanol gas that is needed for the older Mercury engines. ROTAX Claims it is “OLD STALE GAS” and it causes detonation The only time that you need to use non-ethanol gas is if you have a fiberglass gas tank. If thats the case use AV-GAS 100%. If you can’t afford it you shouldn’t be flying! If your state allows non-ethanol gas at the pumps, use it. FRESHNESS IS THE KEY, not ethanol .
- Use Amsoil Interceptor or Quicksilver PWC oil at 40:1 ratio. This is a must to protect your engine life.
- Maximum water temperature is 175 degrees F on takeoff and cruise.
- Maximum EGT is 1200 degrees F. Best EGT is 950 – 1150 with 1050 perfect.
- Only use green antifreeze. Do not use orange Dexcool. If you have a head O-ring leak into the combustion chamber, Dexcool may cause crankshaft failure.
- Warm the engine as soon as it starts at 2500 RPM for 2 minutes. Then increase to 4500 RPM for 4 minutes, and finally at 5000 RPM for 1 minute prior to take off. THIS IS VERY IMPORTANT. You are not just warming the water, you are expanding the cylinders. Try NOT to let the engine run below 4500 RPM once the warm-up is completed. Keep the cylinders expanded. The warm-up time may need to be longer in cold temperature climates.
- Engines purchased have a 2 year warranty. Overhauled engines get a 1 year warranty. Stators on purchased engines have a 90 day warranty. Warranties begin on first flight (except on the stator. USE the Honor system.
- Do not use gas older than 2 months. Do not run ethanol gas in aircraft with fiberglass fuel tanks. The polyester resin will break down and destroy the engine. You should therefore use AV GAS 100 LL. It CAN be mixed 50:50 with non-ethanol fuel to lower your costs. 100 LL gas is always the best for your engine. It’s the very best fuel you can use no matter where you fly, regardless of whichever Rotax 2 stroke engine you have.
- Your engine comes with a 1 hour run-in completed. But for the next 5 hours, you should only use full throttle until you clear the trees on takeoff. If you have a long runway, use full throttle just until airborne. Your pistons will size down in the first 5 hours. Initial clearance is tight until this happens and you could scrape off the cross hatching. Keep in mind that 90% of the engines that fail the damage happened at full throttle.
- While filling the cooling system, remove the water temperature sensor from the cylinder head. Provide coolant until it comes out of the sensor hole. Should the coolant fill before exiting the sensor hole, cover the coolant cap opening with your hand and blow into the overflow hose. This will force any air out of the cylinder head. Repeat until coolant flows out of the water temperature sensor hole. Reinstall the probe and continue until full. Run until 140 Degrees F and then top off.
- During the break-in period, take off at full throttle and then pull the throttle back (to 6000 RPM) after breaking the ground.