Question 1

it's smoking a lot more than it used to, really thick blue smoke even after it's warmed up.

Accepted Answer

DIAGNOSIS Excessive blue smoke means the engine is burning too much oil. This is caused by an over-rich fuel/oil mixture or, less commonly, worn piston rings allowing crankcase oil into the combustion chamber. FIX Verify your fuel mixture ratio. This saw requires a 50:1 mix. Using a 40:1 or 32:1 mix will cause excessive smoke. Drain the tank and mix fresh fuel accurately. Ensure you are using a high-quality 2-stroke oil designed for air-cooled engines. An incorrect carburetor low-speed (L) screw setting too rich can also contribute. IF THAT DIDN'T WORK The carburetor's metering lever is set too high, flooding the engine with fuel. The Zama carburetor on this model has a factory-set metering lever height. Do not adjust it unless you have the proper tool. If the mixture is correct and smoke persists, perform a compression test. A reading below 120 psi indicates worn rings or cylinder damage. HEADS UP Never use automotive motor oil or outboard motor oil in a chainsaw. It does not burn cleanly and will cause excessive carbon buildup and smoke.

Question 2

my chainsaw is vibrating really badly, way more than it used to, makes my hands numb fast.

Accepted Answer

DIAGNOSIS Excessive vibration indicates an imbalance in the rotating assembly. The most likely causes are a bent crankshaft, a failed anti-vibration mount, or a severely unbalanced cutting attachment. FIX First, eliminate the bar and chain as sources. Remove them and run the engine briefly at idle. If vibration is gone, the problem is there. Inspect the bar for straightness and wear. Ensure the chain is properly tensioned and the drive links are not unevenly worn. If vibration persists without the bar, check the four anti-vibration mounts where the engine connects to the rear handle. Replace any that are cracked or squashed. IF THAT DIDN'T WORK The internal crankshaft or engine bearings are damaged. This is a major repair. Signs include a visible wobble in the clutch drum when the engine runs or metallic grinding noises. This requires complete engine disassembly. HEADS UP Continued use with severe vibration will damage every component in the saw and is a significant safety risk. Stop using it until the source is found and fixed.

Question 3

the chain brake on my 455 feels really stiff and is hard to engage by hand, sometimes it doesn't snap back off.

Accepted Answer

DIAGNOSIS The brake band mechanism is binding due to sawdust, dirt, or a lack of lubrication. The pivot points for the brake lever and the band itself are gummed up. This is a maintenance issue, not a part failure. FIX Thoroughly clean the entire clutch cover area. Remove the side cover. Manually work the brake lever back and forth while spraying a degreaser like brake cleaner into the pivot points. Flush out all debris. Apply a light machine oil (not grease) to the pivot pin and the areas where the band contacts the guide plate. Operate the lever dozens of times to free it. IF THAT DIDN'T WORK The brake band may be deformed or the return springs are weak or broken. You must replace the chain brake assembly. This includes the band, springs, and lever mechanism as a kit, part # 537160601. Ensure the band is correctly routed around the clutch drum during reassembly. HEADS UP Never operate the saw with a malfunctioning chain brake. In a kickback event, it will not stop the chain. Test the brake by running the saw at idle and slapping the front hand guard forward. The chain should stop instantly.

Question 4

it starts and runs for about 30 seconds then just shuts off like i hit the switch, and won't restart until it's cold again.

Accepted Answer

DIAGNOSIS This is a classic symptom of a failing ignition coil. When the coil heats up, its internal winding fails and kills the spark. The engine shuts off abruptly. When it cools, contact is temporarily restored. FIX Confirm the diagnosis with a spark test when the saw is hot and failed. Remove the spark plug, reconnect the boot, ground the plug against the cylinder, and pull the starter. Observe for a strong blue spark. If there is no spark when hot, replace the ignition coil. The correct part is Husqvarna 544018401. IF THAT DIDN'T WORK The problem could be a faulty ignition switch or a break in the stop switch wire. Disconnect the two wires from the ignition coil that go to the stop switch. Try starting the saw. If it runs and does not shut off prematurely, the switch or its wiring is faulty and must be replaced. HEADS UP When replacing the coil, the air gap between the coil legs and the flywheel magnets is critical. Use a business card or the specified 0.3mm feeler gauge to set the gap. Incorrect gap causes weak spark or no start.

Question 5

the chain stops moving while i'm cutting even though the engine is still running at full throttle.

Accepted Answer

DIAGNOSIS The clutch is slipping or the drive sprocket is worn out. This is a mechanical failure due to normal wear or a loose chain. A dull chain exacerbates this by increasing load. FIX First, check chain tension. A properly tensioned chain should snap back against the bar when pulled from the underside. If tension is correct, inspect the clutch and sprocket. Remove the side cover and clutch cover nut. The clutch drum and rim sprocket should be replaced as a set if the sprocket teeth are visibly hooked or worn down. Part # 503847001 for the rim sprocket kit. IF THAT DIDN'T WORK The clutch springs have lost tension or the clutch shoes are glazed. The entire clutch assembly (part # 501879201) must be replaced. You need a clutch removal tool to compress and remove the clutch from the crankshaft. Ensure the chain brake band is not partially engaged and dragging. HEADS UP A dull chain is the leading cause of clutch and sprocket wear. Always cut with a sharp chain. Never run the saw with the chain brake engaged, as this destroys the clutch.

Question 6

my 455 rancher is leaking bar oil all over my garage floor even when it's just sitting there not running.

Accepted Answer

DIAGNOSIS Bar oil is siphoning from the tank through the oil pump. This is almost always caused by a missing or damaged oil tank vent. The vent is a small one-way valve on the oil tank cap or body. FIX Locate the oil tank vent. On this model, it is integrated into the oil filler cap assembly. Remove the cap. Clean the small vent hole in the cap with a thin wire. Blow compressed air through it from the inside. If oil still leaks, the entire oil cap assembly (part # 537210301) must be replaced. IF THAT DIDN'T WORK The oil pump itself has failed and is stuck in the open position. This requires removing the side cover and clutch assembly to access the pump. Replace the entire oil pump assembly, part # 537210701. Ensure the oil feed line from the tank to the pump is securely connected. HEADS UP Never store the saw on its side with oil in the tank. Always store it upright. Bar oil will degrade rubber and plastic, so clean any spilled oil off the saw's housing immediately.

Question 7

chainsaw starts and idles but immediately dies when i give it throttle. acts like it's being choked.

Accepted Answer

DIAGNOSIS The engine is running too lean at high speed. This is a fuel delivery or air intake issue. The most common cause is a clogged fuel filter in the tank or an incorrect carburetor high-speed (H) screw setting. FIX Check the fuel filter first. Remove the fuel line from the tank and inspect the filter. If it's dark brown or clogged, replace it. Next, check the carburetor adjustment screws. With the engine warmed up, turn the H screw clockwise until it lightly seats, then turn it counter-clockwise 1 full turn. This is the baseline setting. Test the throttle response. IF THAT DIDN'T WORK The carburetor's fuel pump diaphragm is likely stiff and not pumping enough fuel. The saw uses a Zama C1Q-S267 carburetor. The diaphragm kit part number is 530035185. Replace the entire diaphragm and gasket set. Also check for air leaks at the carburetor mounting gasket. HEADS UP Adjusting the H screw more than 1.5 turns out from seated can cause a dangerously lean condition and engine seizure. Always retune after replacing any fuel system component.

Question 8

my husqvarna 455 rancher ran fine last season, now it won't start at all, not even a pop. pull cord feels normal.

Accepted Answer

DIAGNOSIS The engine is not getting fuel. Old, degraded fuel has clogged the carburetor jets and fuel lines. Ethanol-blend gas left in the system for over 30 days is the primary cause. FIX First, drain all old fuel from the tank and the carburetor bowl. Replace it with fresh, ethanol-free fuel mixed with a high-quality 2-stroke oil at a 50:1 ratio. Prime the system with the purge bulb until you see fuel in the clear line. Pull the starter cord 5-6 times with the choke on. If it still doesn't pop, the carburetor needs cleaning. IF THAT DIDN'T WORK The carburetor diaphragm has hardened or the internal jets are fully blocked. You must disassemble and clean the carburetor. Soak the metal carburetor body and jets in carburetor cleaner. Replace the entire carburetor diaphragm and gasket kit. Reassemble with the factory default settings: H screw 1 turn out, L screw 1 turn out. HEADS UP Never store this saw with fuel in the system. Always run it dry or use a fuel stabilizer. Using ethanol-blended fuel will guarantee a repeat of this problem.

Husqvarna 455 Rancher Gas Chainsaw

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