Stihl Ht 75 Owners Manual
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20 english HT 70, HT 75 For automatic and reliable lubrication of the chain and guide bar: Use only a quality, environmentally compatible chain and bar lubricant. STIHL chain lubricant with non-fling additive or the rapidly biodegradable STIHL BioPlus is recommended. Biological chain oil must be resistant to aging (e.g. STIHL BioPlus) since it will otherwise quickly turn to resin. This results in hard deposits that are difficult to remove, especially in the area of the chain drive and chain. It may even cause the oil pump to seize. The service life of the chain and guide bar depends on the quality of the lubricant. It is therefore essential to use only a specially formulated chain lubricant!If special chain lubricant is not available, you may – in an emergency – use an HD single grade or multigrade engine oil with a viscosity that suits the prevailing outside temperature. Do not use waste oil! Waste oil does not have the required lubricating properties and is unsuitable for chain lubrication. Medical studies have shown that renewed contact with waste oil can cause skin cancer. It also harms the environment!A full chain oil tank is sufficient for about one tankful of fuel. Check the oil level regularly during cutting work. Never allow the oil tank to run dry! :Thoroughly clean the filler cap and area around it so that no dirt can fall into the tank. :Position the unit so that the filler cap faces up. If the oil level in the tank does not change, this may be due to a problem in the oil supply: Check chain lubrication, clean the oilways, contact your STlHL dealer for assistance if necessary.Chain Oil Filling Chain Oil Ta n k 390BA047 KN
21 HT 70, HT 75english The bayonet-type oil tank filler cap with its hinged clip can be opened and closed without tools. :To open the tank, swing the clip (1) to the vertical position. :Turn the filler cap counterclockwise as far as stop and remove. :Fill up with chain oil. :To close the oil tank, place the filler cap in position with the clip vertical, making sure the recesses (2) are in alignment. :Turn the filler cap clockwise as far as stop. :Fold the clip down so that it is flush with the top of the cap.The saw chain must always throw off a small amount of oil. :Always check chain lubrication and the oil level in the tank before starting work. Never operate your pruner without chain lubrication. If the chain is run dry, the whole cutting attachment will be irretrievably damaged within a very short time. Inadequate lubrication can be caused by a dirty oil strainer: Have the oil strainer cleaned or replaced by your STIHL dealer. Every new chain has to be broken in for about 2 to 3 minutes. After breaking in the chain, check chain tension and adjust if necessary – see chapter Checking Chain Tension.Always shut down the engine and put on the chain guard! :Slacken off the screw. :Adjust shaft to required length. :Tighten the screw firmly. 247BA011 KN 12 Checking Chain Lubrication 390BA048 KN Adjusting Telescopic Shaft(HT 75) 390BA049 KN390BA049 KN
22 english HT 70, HT 75Shoulder strap*:Put on the shoulder strap (1). :Adjust length of strap so that the spring hook (2), with the unit attached, is at about the same height as your right hip. * see “Guide to Using this Manual“ Full harness*:Put on the full harness (1) and sling (2) as shown on the instruction sheet supplied. :Adjust the harness and thigh belt (3) as required. :Rest the powerhead in the sling during cutting work. *see “Guide to Using this Manual” Fitting the Harness 21 390BA040 KN 21 390BA040 KN 386BA012 KN 2 1 3
23 HT 70, HT 75english ControlsThrottle trigger interlock (1), throttle trigger (2) and slide control (3) with the positions: START (4) The normal run position # (5) and $ – STOP (6) for stopping the engine.. Starting:Hold down the trigger interlock and squeeze the throttle trigger. :Keep both levers in that position. :Move the slide control to START position and hold it there. :Now release the throttle trigger, slide control and trigger interlock in that order. This is the starting-throttle position.If engine is cold: Set the choke lever (8) to g If engine is warm: Set the choke lever (8) to e Also use this setting if engine has been running but is still cold. :Press the fuel pump bulb (9) at least five times, even if the bulb is still filled with fuel. Starting / Stopping the Engine 3 231 STOP 4 5 6 002BA149 KN 393BA017 KN 8 8 393BA018 KN 9
24 english HT 70, HT 75 :Place the unit on the ground: It must rest securely on the engine support and the hook. :Remove the chain guard. Check that chain is not touching any object or the ground. If necessary, rest the hook on a raised support (e.g. a branch, mound or something similar). Check that nobody is standing within the working range of the pruner.. :Make sure you have a firm footing: Press the unit firmly against the ground with your left hand on the fan housing. Your thumb should be under the fan housing. Do not stand or kneel on the drive tube. This will bend the tube and result in permanent damage to the telescopic shaft. 390BA022 KN
25 HT 70, HT 75english Alternative method: :Remove the chain guard. Position the shaft on a branch so that it is held by the hook. :Hold the unit firmly with your left hand around the fan housing – your thumb under the fan housing.:Pull the starter grip slowly with your right hand until you feel it engage – and then give it a brisk strong pull. Do not pull out starter rope to full length – it might break. :Do not let the starter grip snap back – guide it slowly into the housing so that the starter rope can rewind properly.When engine begins to fire: :Move choke lever to e :continue cranking. As soon as engine runs: :Blip the throttle trigger – the slide control moves to the run position #, and the engine returns to idling speed. Make sure carburetor is correctly adjusted – chain must not run when engine is idling. Your pruner is ready for operation. To shut down engine: :Move the slide control in direction of c to $. 390BA009 KN
26 english HT 70, HT 75At very low temperatures As soon as engine runs: :Blip the throttle trigger – the slide control moves to the run position #, and the engine returns to idling speed. :Open throttle slightly – warm up engine for short period. If the engine does not startIf you did not move the choke to e quickly enough after the engine began to fire, the combustion chamber is flooded. :Set choke lever to e. :Set slide control, interlock lever and throttle trigger to starting throttle position. :Start the engine – pull the starter rope briskly – 10 to 20 pulls may be necessary.If the engine still does not start :Move the slide control in direction of c to STOP – $. :Pull off the spark plug boot (10). :Unscrew and dry off the spark plug. :Open the throttle fully. :Pull the starter rope several times to clear the combustion chamber.:Fit the spark plug – use combination wrench to tighten it down. :Connect the spark plug boot and press it down firmly. :Move the slide control to START. :Set choke lever to e even if engine is cold. :Now start the engine. Throttle cable Check adjustment of the throttle cable – see Adjusting the Throttle Cable. Fuel tank run until dry:After refueling, press the fuel pump bulb at least fives times – even if the bulb is filled with fuel. :Set choke lever to suit engine temperatire. :Now start the engine. 393BA019 KN 10
27 HT 70, HT 75english During break-in periodA factory new machine should not be run at high revs (full throttle off load) for the first three tank fillings. This avoids unnecessary high loads during the break-in period. As all moving parts have to bed in during the break-in period, the frictional resistances in the engine are greater during this period. The engine develops its maximum power after about 5 to 15 tank fillings. Do not make the mixture leaner to achieve an apparent increase in power – this could damage the engine – see chapter “Adjusting the Carburetor”.During operationCheck chain tension frequently! A new chain has to be tensioned more often than one that has been in use for some time.Cold chain Tension is correct when the chain fits snugly against the underside of the bar and can still be pulled along the bar by hand. Retension if necessary – see chapter “Tensioning the Saw Chain”. Chain at operating temperature The chain stretches and begins to sag. The drive links on the underside of the bar must not come out of the bar groove – the chain may otherwise jump off the bar. Retension the chain – see chapter “Tensioning the Saw Chain”. Always slacken off the chain again after finishing work. The chain contracts as it cools down. If it is not slackened off, it may damage the crankshaft and bearings.After a long period of full-throttle operation Allow engine to run for a while at idle speed so that the heat in the engine can be dissipated by flow of cooling air. This protects engine-mounted components (ignition, carburetor) from thermal overload. After finishing work:Slacken off the chain if you have retensioned it at operating temperature during cutting work. The chain contracts as it cools down. If it is not slackened off, it may damage the crankshaft and bearings. Wait for engine to cool down. Drain the fuel tank. Store the machine in a dry place. Check tightness of nuts and screws (not adjusting screws) at regular intervals and retighten as necessary. Operating Instructions
28 english HT 70, HT 75 :Turn the bar over – every time you sharpen the chain – and every time you replace the chain – this avoids one-sided wear, especiallly at nose and underside of the bar. Regularly clean 1 =oil inlet hole 2 =oil passage 3 =bar groove:Measure groove depth – with scale on filing gauge – see “Special Accessories“ – in area used most for cutting on Rollomatic bars. If groove depth is less than specified: :Replace the guide bar. The drive link tangs will otherwise scrape along the bottom of the groove – the cutters and tie straps will not ride on the rails.Dirty air filters reduce engine power increase fuel consumption and make starting more difficult. If there is a noticeable loss of engine power :Move choke lever to g. :Press in the tab (1). :Ease the filter cover (2) over the tab and take it away. :Clean away loose dirt from around the filter. :Remove the foam and felt filter elements.Taking Care of Guide Bar 3 2 1 390BA050 KN Chain type Chain pitch Minimum groove depth Picco-Mini 3/8 P 5.0 mm (0.20) Cleaning the Air Filter 355BA014 KN 2 1
29 HT 70, HT 75english :Wash the foam element in a clean, non-flammable cleaning solution (e.g. warm soapy water) and then dry. :Fit new felt element. As a temporary measure you can knock it out on the palm of your hand or blow it out with compressed air. Do not wash. Replace damaged parts! :Install the foam element (3) in the filter cover (2). :Place felt element (4) (lettering facing inward) in filter housing (5). :Fit filter cover so that it snaps into position.Exhaust emissions are controlled by the design of the fundamental engine parameters and components (e.g. carburation, ignition, timing and valve or port timing) without the addition of any major hardware. The carburetor comes from the factory with a standard setting. This setting provides an optimum fuel-air mixture under most operating conditions. With this carburetor it is only possibleto adjust the engine idle speed within fine limits. 2 3 355BA031 KN 4 5 355BA032 KN Motor Management Adjusting the Carburetor 265BA024 KN LA HL 1 3 / 4