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:: LPG Vapour Conversion System ::

HellCat 360cc 4 stroke engine LPG Conversion:


Liquid Petroleum Gas (LPG) also called Propane is the latest addition to marry in with either the standard Twin carburetor design or the recent Petrol Injection version of the ever popular HellCat engine.

This Vapour LPG system works off the propane vapour inside the bottle, when you let gas out of the bottle more propane evaporates off the top of the liquid propane in the bottle, the same as a barbeque. Propane starts to evaporate at -40 Celsius, so no chance of freezing under normal conditions. That's the main reason they use nearly pure propane for BBQ/camping gas (portable gas), gas will continue to evaporate at a similar rate even when really cold. In cars we use the heat of the engine to evaporate the gas, so we can get away with a 50/50 mix of propane/butane, as Butane starts to evaporate at zero Celsius. One litre of liquid LPG expands to 270 litres of combustible vapour.

After countless months of research we have finally soured all the parts needed to convert our HellCat engine, this image shows 9kg (20lb) Steel commercial LPG configuration with Liquid fill, Vapour decanter & Gauge as standard fittings for our twin cylinder HellCat LPG kit, this Kit with domestic hoses & Fittings costs $500.00, can be either fitted to the Carburetor or Fuel Injection engine, a commercial Steel 9kg LPG Tank with a tare weigh of 12.2kg & cost $250, Aluminium Tank weighs 7.7kg is $350, either tank can hold 17lt of liquid and come standard with Service Station LPG bowser fill valve, Acme RHT decanter valve, Gauge, a Vertical Tank mounting Bracket is $80, as you don't need the standard plastic petrol tank for the Cage and Quad & mounting bracket you get a deduction for that, the Full LPG kit cost starts from $730.00 +Freight.

Prior to LPG Kit Installation:

It is not recommend converting engines with under 25 hours or running time, this is to ensure the engine runs correctly on gasoline and does not have any underlying issues from the manufacture.

Like wise it is not recommended to convert an engine with over 500 unless it was well maintained & retain near new compression. Many engines used in commercial settings are not properly maintained and have significantly lowered compression due to component ware starting after 500 of use. Lower compassion due to wear will affect an engine running on gasoline slightly but when converting the same engine to propane the lower compression will severally affect the performance the engine on LPG.

For the best engine life and performance, we recommend you check your oil and replace it with a high grade synthetic blend of motor oil applicable to your engine before installing our Cleaner Greener LPG Conversion Kit. Any engine that you intend on converting to propane fuel should be in good running condition before attempting to install this kit.

Check compression, it must be above 830kpa (120psi). If compression is below 830kph the performance of the engine on propane vapour will be less than optimal. Engines with significantly lower than factory compression will have less than optimal performance on propane vapour fuel.

Inspect valves and adjust to manufacture specifications, if you are intending fitting our LPG kit to another engines not fitted with Hi-Nickel content valve seats may need to adjust valves .002 wider than factory settings per Technical Manual &/or fit a Upper cylinder drip lubrication kit.

Remember: For best engine life we recommend running the engine on high quality synthetic oil !

All spark plugs must/should be changed to Iridium Platinum spark plugs.
The standard Spark Plug is NGK-CR9EK with Nickel Centre & Ground Electrode, better if replaced with NGK-CR9EKP with Platinum Centre & Nickel Ground Electrode, but an Iridium Platinum Plug !

A Champion RG-94C replace is another standard plug that can be replaced an Iridium equivalent.

The stock spark plugs used in Petrol/gasoline engines rely on the carbon in fuel to help arc the plug.
Since there is no carbon in propane fuel, the spark plug is the only conductor of the electrical current, causing the standard plug to burn out sooner. We therefore suggest frequent maintenance of the spark plugs used in engines which have our LPG Conversion Kit.
Inspect spark plug gap and adjust to .035-.040 gap, clean or replace the spark plug to ensure proper
easy starts.

Installing this LPG Kit:

  1. First remove the 3 allan key bolts from both LHS and RHS black intake manifolds (put them in a container), then you will be able to lift one sides and pull it out of Air filter body off the cylinder head and then pull the carby end out off the air filter housing, making sure Not to loose the dust seals "O" rings.
  2. Now stuff a clean large piece of cotton Cloth or Foam block down inside the Intake Manifolds on each side, this is to stop Aluminium debris entering into the cylinder head whilst you are carefully drilling the correct size holes to be threaded.
  3. Once the intake jets are drilled and threaded use compressed air and make sure you blow all the debris from drilling and threading from both holes and intake ports.
  4. Once the intake jets are drilled and threaded they should look like this.
  5. It is recommended you clean the Threads then use a Liquid LPG sealant or LPG thread tape (LPG tape is NOT plumbing tape), it will be easier to first seal and tighten the 90° elbow onto the straight jet and then fit pares remembering to turn both 90° elbows the facing forwards.
  6. Insert the Two intake restrictors, one on each outer side of the last carby rings, making sure they are inserted tightly so not to fall out, then Re-fit the Carburetors into the Air Filter & Foam housing cover, making sure the outer rubber "O" ring dust seals are fitted correctly, we highly recommend using Two long zip ties placed on the outer edges of the foam air box cover (Part: 36M-21-03), this is required to stop dirt and dust entering the small gaps. We are currently looking at replacing the original air filter housing as we feel the is not that good.
  7. Next Fit the hoses from the intake jets to the out-flow on Vacuum Converter.
  8. Without over stretching the commercial lines, locate the LPG converter as low as possible to get a low as possible centre of gravity (CG), remember you must Fit the LPG Regulator assembly Vertically, preferably on one of the Quad bars or in a position so that the Double hoses have enough length to reach the outer sides of the Carburetors.
  9. You can locate and fit a LPG Tank where ever you like as long as the Hose from the Tank is long enough to reach the Regulator.
  10. Once all the hoses are fitted and tightened, get a small spray bottle and mix a cup of water and a teaspoon of common dishwashing liquid.
  11. Now open the main LPG tank knob and the Regulator mixture knob open 2.5 turns (gas should not escape into the cylinder head lines unless you press the purge button or attempt to start the engine), now spray all the joints up to the the Regulator knob and the large diaphragm housing with the soppy water, if there any leaks in the joins, hoses and diaphragm housing bubbles will appear, it is a good idea to check even new lines just to be sure, if there any leaks stop and fix them before proceeding any further.
  12. The reason we haven't tested the hoses from the large Vacuum activated diaphragm and the lines to the Intake manifolds is that there won't be any gas entering the lines until a vacuum is created by the engine actually running, that is one of the safety features of this kit, if the engine stalls or quits the Gas automatically stops until the engine is restarted.
  13. The hoses from the Diaphragm outlet to the intake orifices are not as important to test as these work on vacuum, so any small leek in these hoses is not as important, however any large leaks will only draw air into the line(s) reducing the vacuum and causing the engine to stall from lack a vacuum.
  14. The standard Thermostat (part No. 36C-22-01) appears perfect for LPG as LPG will atomise at a lower temperature than petrol, an engine will run better with a lower operating temperature, the manual states the Maximum operating Temperature as being 85°C (192°F), any hotter operating temperature for more than five minutes in an emergency may damage the engine.

Starting your engine on LPG for the first time:

  1. Check engine water & oil level and if previously run on Petrol, start the engine and run it until the engine has used all the petrol that may have been in the carburetors.
  2. Open the LPG Tank knob 1 or 2 turns, now turn the Regulator mixture knob out 2.5 turns, do not try to adjust any mixture screws on the regulator or the diaphragm as they have been purposely glued into the correct position to save errors.
  3. Carefully press the Purge button once or twice on top of the on the large Diaphragm (Do Not over force this button or you may damage the mechanism)
  4. Now attempt to start the engine do Not wind the starter motor over for more than 5 seconds or you may overheat and burn out the starter motor &/or the Black box.)
  5. Set idle to 2300—2600 RPM by adjusting the Regulator knob in or out until it idles smoothly as approx. rpm. (engine must run smooth - otherwise increase idle RPM)
  6. Now see if your engine will rev out to 7'800rpm for a sew seconds, if not you will have to enlarge the intake venturi washers until it will.

Note: The standard engine Timing @3000 RPM should be within the range of 25~27° BTDC.  We have yet to confirm what the total advanced timing is.

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