Husqvarna 545 and 550XP Mark II: generation-specific service
The 545/550XP Mark II manual specifies CMR6H at 0.5 mm, with 0.53 L fuel and 0.32 L chain-oil reservoirs. Mark II is part of the parts identity: Husqvarna lists kit599334301 for 545II/550XPII and 599333901 for 545/550XP Gen1. A seller’s plain550XP description does not distinguish them.
Read the generation before buying the kit
The two official kit listings contain service filters and a plug but name different generations. Match the saw label, serial and applicable parts catalog before ordering. A familiar cover or matching0.5 mm gap is not proof that the earlier kit fits.
Keep the generation in a written service record and any used-sale description. Request a label photograph if a listing abbreviates it. Buying a kit before identifying the saw can leave the actual air-filter or plug requirement unresolved.
| Mark II service identity | Capacity, plug or kit |
|---|---|
| Fuel /chain-oil tanks | 0.53 /0.32 L |
| Plug /gap | CMR6H /0.5 mm |
| Mark II kit | 599334301 |
| Gen1 kit, different applicability | 599333901 |
Do not confuse the two oil jobs
The 2019 Mark II manual’s 0.53 L fuel reservoir uses 50:1 premix, while the 0.32 L chain-oil reservoir supplies the attachment. For an example 1.5 L gasoline batch at 50:1, measure30 ml of qualifying two-stroke oil. The larger reservoir volume is not a recipe for mixing the two reservoirs’ contents.
The cited maintenance instructions include monthly plug replacement or earlier when required. Use the model’s approved attachment table and its lubrication checks rather than a Rancher’s bar-length oil-pump setting. A common displacement class does not establish the same chain, filter or kit.
Check the chain brake, controls, attachment, lubricant supply and leaks as directed before use. Stop for a failed brake or a chain that moves at idle. Follow the complete repair procedure for recoil, clutch and carburetor work instead of borrowing a setting from another generation.
545/550 XP Mark II, 2019 manual, 545II/550XPIIkit, Husqvarna 545/550XP Gen1 kit599333901
Husqvarna 545 and 550 XP Mark II chainsaws: fuel mix, spark plug and tune-up kit
The Husqvarna 545 Mark II and 550 XP Mark II run on a 50:1 mix, 2½ fluid ounces of two-stroke oil per US gallon, in a 0.53 liter tank, with a separate 0.32 liter chain oil tank. The spark plug is an NGK CMR6H gapped 0.5 mm, replaced monthly or sooner. Husqvarna’s tune-up kit is 599 33 43-01 for the Mark II and 599 33 39-01 for the Gen I, each with an air filter, fuel filter and plug.
Stop the engine and pull the spark plug cap before any service, let the muffler cool, and refuel outdoors away from sparks.
A 50 cc pro saw with two tanks and one plug
The Husqvarna 545 Mark II and 550 XP Mark II share one 50.1 cc two-stroke engine, an idle speed of 2,800 RPM and a 0.53 liter (1.12 US pint) fuel tank. The 550 XP is the higher-rated of the two, at 3.0 kW (4.0 hp) at 10,200 RPM against 2.7 kW (3.6 hp) at 9,900 RPM for the 545. The G versions add a heated handle and carburetor.
Like every saw here, the engine has no crankcase oil to change: it burns oil mixed into the fuel, and a separate 0.32 liter (0.68 US pint) tank feeds chain oil to the bar through an adjustable pump.
| Item | Specification |
|---|---|
| Displacement | 50.1 cc |
| Power | 545: 2.7 kW (3.6 hp) at 9,900 RPM; 550 XP: 3.0 kW (4.0 hp) at 10,200 RPM |
| Idle speed | 2,800 RPM |
| Fuel mix | 2% (50:1) with Husqvarna two-stroke oil for air-cooled engines |
| Fuel tank | 0.53 L (1.12 US pint) |
| Chain oil tank | 0.32 L (0.68 US pint); adjustable oil pump |
| Spark plug | NGK CMR6H |
| Electrode gap | 0.5 mm (0.020 in) |
| Drive sprocket | Rim, 7 teeth |
| Weight without cutting equipment | 545 and 550 XP 11.7 lb (5.3 kg); G models 12.1 lb (5.5 kg) |
| Gasoline | Two-stroke oil (2%) |
|---|---|
| 1 US gallon | 2½ US fl oz |
| 2½ US gallons | 6½ US fl oz |
| 5 US gallons | 12⅞ US fl oz |
| 5 liters | 0.10 liter |
| 10 liters | 0.20 liter |
Parts to buy for the Husqvarna 545 and 550 XP Mark II chainsaws
Husqvarna sells a tune-up kit for each generation of these saws, and it holds an air filter, a fuel filter and a spark plug. Which one you need depends on whether your saw is the first generation or the Mark II.
| Part | Part number | Notes |
|---|---|---|
| Tune-up kit, Mark II | 599 33 43-01 | For the 545 II and 550 XP II: air filter, fuel filter and spark plug. |
| Tune-up kit, Gen I | 599 33 39-01 | For the 545 and 550 XP Gen I. |
| Spark plug | NGK CMR6H | Gap 0.5 mm; NGK lists it as the standard plug for the 550 XP. |
| Fuel mix oil | Husqvarna two-stroke oil | 50:1; or Husqvarna premixed alkylate fuel. |
The maintenance chart
Husqvarna’s chart is by day, week and month, and the monthly line holds the plug. The manual says to replace the spark plug monthly or more often if necessary, which is far more frequent than most chainsaw makers print.
| When | What |
|---|---|
| Daily | Clean the outside of the saw and the handles; check the throttle trigger and lockout, the vibration dampers, the chain brake, the chain catcher, the guide bar and its lubrication, and the saw chain and its tension; clean the air intake on the starter. |
| Weekly | Clean the cooling system, check the starter and rope, lubricate the needle bearing, deburr the guide bar, clean or replace the spark arrestor mesh, clean the carburetor area, clean or replace the air filter and clean between the cylinder fins. |
| Monthly | Check the brake band, clutch center, drum and spring; clean the spark plug; clean the carburetor’s outside; check the fuel filter and fuel hose and replace if necessary; check cables and connections; empty the fuel tank and the oil tank. |
| Every month or sooner | Replace the spark plug. |
For the run-in, do not run the saw at full throttle without load during the first 10 hours. And do not mix fuel for more than a month of use: the manual warns that stale mixed fuel damages the engine, which is why the monthly line empties the tank. See the two-stroke fuel mix calculator for any batch size.
50:1
Fuel to oil
2½ US fl oz of oil per US gallon.
CMR6H
NGK spark plug
Gap 0.5 mm; replace monthly or sooner.
599 33 43-01
Mark II tune-up kit
Air filter, fuel filter and spark plug.
Husqvarna 545 and 550 XP Mark II chainsaws: questions
What is the fuel mix for a Husqvarna 550 XP Mark II?
50:1, meaning 2% oil: 2½ US fluid ounces of Husqvarna two-stroke oil per US gallon of gasoline, or 0.10 liter per 5 liters. Husqvarna also sells premixed alkylate fuel as an alternative.
What spark plug does a Husqvarna 550 XP Mark II use?
An NGK CMR6H with the electrode gap set to 0.5 mm (0.020 in), per Husqvarna’s technical data. NGK’s catalog lists the CMR6H as the standard plug for the 550 XP.
How often should I replace the spark plug on a Husqvarna 545 Mark II?
Monthly, or more often if necessary, according to the operator’s manual. The monthly maintenance line also has you clean the plug and check the fuel filter and hose.
What is the Husqvarna 550 XP Mark II tune-up kit number?
599 33 43-01 for the 545 II and 550 XP II, holding an air filter, fuel filter and spark plug. The first-generation 545 and 550 XP use 599 33 39-01.
How big are the fuel and chain oil tanks on a Husqvarna 550 XP Mark II?
The fuel tank holds 0.53 liter (1.12 US pints) and the chain oil tank holds 0.32 liter (0.68 US pint). The oil pump is adjustable.
What is the run-in for a Husqvarna 545 Mark II?
During the first 10 hours, do not run the saw at full throttle without load. The manual gives the run-in so the engine wears in before it is worked hard.
What is the difference between the Husqvarna 545 Mark II and 550 XP Mark II?
Power. The 550 XP is 3.0 kW (4.0 hp) at 10,200 RPM and the 545 is 2.7 kW (3.6 hp) at 9,900 RPM, from the same 50.1 cc engine. The tanks, plug and kit are the same.
How often do I clean the air filter on a Husqvarna 550 XP Mark II?
Weekly, per Husqvarna’s chart, brushing or shaking it clean; it says a filter used a long time cannot be fully cleaned, so replace it regularly. The tune-up kit includes a new one.
What does the Husqvarna 550 XP Mark II monthly maintenance include?
Checking the brake band, clutch center, drum and spring, cleaning the plug and the carburetor’s outside, checking the fuel filter, hose and cables, and emptying the fuel and oil tanks.
What is the idle speed on a Husqvarna 550 XP Mark II?
2,800 RPM, the same as the 545 Mark II. The manual gives the maximum power as 3.0 kW at 10,200 RPM for the 550 XP.
How much oil do I add to a gallon of gas for a Husqvarna 545?
2½ US fluid ounces per US gallon for the 50:1 mix, or 6½ ounces for 2½ gallons and 12⅞ ounces for 5 gallons. Use two-stroke oil for air-cooled engines.
Why does Husqvarna say to empty the fuel tank monthly?
Mixed fuel goes stale and damages the engine and carburetor, and the manual warns against mixing more than a month’s supply. Emptying the fuel and oil tanks is on the monthly chart.
What is the electrode gap on a Husqvarna 545 Mark II spark plug?
0.5 mm (0.020 in). Husqvarna warns to use the recommended plug type, because the wrong plug can damage the piston and cylinder.