Husqvarna 125B blower service: plugs and manual revisions
For a 125B, confirm the actual serial and applicable manual before buying a spark plug. The older 125B/BX/BVX document contradicts its own plug table and maintenance text; current US 125B support lists RCJ-6Y. Backpack 130BT/350BT plug and fuel instructions have their own service guide.
Resolve the 125B’s old plug discrepancy
The 2010 125B/BX/BVX manual prints RCJ-6Y in its technical table but RCJ-8Y in its maintenance text. Husqvarna’s current 125B product support identifies Champion RCJ-6Y. Use the manual and part confirmation for the actual serial, rather than treating the two old names as approved equivalents.
Keep the handheld oil instruction with its revision
The older manual distinguishes 50:1 with Husqvarna oil from 33:1 with other qualifying air-cooled oil. Do not silently replace that instruction with a backpack manual’s rule or treat it as approval for straight gasoline. Confirm the actual market manual and qualifying oil before mixing.
For a one-liter gasoline batch, the arithmetic is 20 ml at 50:1 and about 30.3 ml at 33:1. Those examples show why the qualifying-oil instruction matters; they do not select an oil for a different revision. Stop and cool before refueling, and follow the applicable handheld guards, inlet and vacuum-attachment procedures.
| Source surface | Printed identity |
|---|---|
| 2010 technical table | RCJ-6Y |
| 2010 maintenance text | RCJ-8Y |
| Current 125B support | RCJ-6Y |
Husqvarna 125B leaf blower: fuel mix, spark plug, filters and maintenance schedule
The Husqvarna 125B, 125BX and 125BVX blowers run a 1:50 (2%) mix with Husqvarna two-stroke oil, or 1:33 (3%) with another good oil, in a 0.5 liter tank. The plug is a Champion resistor type, listed as an RCJ-6Y in the technical data and an RCJ-8Y in the maintenance text, gapped 0.6 millimeter. Husqvarna’s schedule has the air filter cleaned daily, the plug checked weekly, and the fuel filter, plug and air filter changed monthly.
Stop the engine and let it cool for a few minutes before refuelling, open the fuel cap slowly so pressure escapes gently, and move the machine away from the refuelling area before you start it. Figures come from Husqvarna’s 2010 operator’s manual for the 125B, 125BX and 125BVX, listed in the sources.
A 28 cc two-stroke: mix, plug and a monthly rhythm
The Husqvarna 125B is a handheld leaf blower with a 28 cc two-stroke engine, a 35 mm bore and 28.7 mm stroke, rated 0.8 kilowatt. The 125BX and 125BVX are the same engine with a vacuum and bag kit. All three have a catalytic converter muffler, idle at 2,800 to 3,200 RPM and reach 8,600 RPM blowing.
As a two-stroke they have no sump, and their whole maintenance story is the fuel, the plug, the air filter and the fuel filter.
| Item | Specification |
|---|---|
| Fuel to oil ratio | 1:50 (2%) with Husqvarna two-stroke oil; 1:33 (3%) with another good-quality air-cooled two-stroke oil |
| Two-stroke oil to avoid | Never outboard oil for water-cooled engines, and never four-stroke engine oil |
| Fuel tank | 0.5 L |
| Spark plug | Champion RCJ-6Y in the technical data; the maintenance text says a resistor plug Champion RCJ-8Y or equivalent |
| Electrode gap | 0.6 mm |
| Idle and maximum speed | 2,800 to 3,200 RPM; 8,600 RPM blowing, 7,500 RPM vacuuming (BX and BVX) |
| Weight, without fuel | 4.3 kg (125B); 4.4 kg (125BX and 125BVX) |
| Gasoline | Oil at 2% (1:50) | Oil at 3% (1:33) |
|---|---|---|
| 5 liters | 0.10 liter | 0.15 liter |
| 10 liters | 0.20 liter | 0.30 liter |
| 15 liters | 0.30 liter | 0.45 liter |
| 20 liters | 0.40 liter | 0.60 liter |
Two plug numbers appear in one manual: the technical data table lists an RCJ-6Y and the maintenance section names an RCJ-8Y. Both are Champion resistor plugs, and the manual sets the gap at 0.6 mm either way, so check the label on the engine or ask a Husqvarna dealer for the plug your serial number takes. Mix in a clean container made for fuel.
Husqvarna gives the 3% ratio only for other makers’ oil, and 2% for its own.
The schedule Husqvarna prints
| When | What |
|---|---|
| Daily | Clean the outside; check the variable speed control, throttle trigger and stop switch; clean the air filter and replace it if necessary; check nuts, screws and housings. On the BX and BVX also check the inlet cover locks, that the fan impeller is clean and that the bag is intact. |
| Weekly | Check the starter, cord and tensioning spring and the air intake at the starter; clean the outside of the spark plug, check the gap and adjust it to 0.6 mm or replace the plug; clean the fan blades on the flywheel; clean or replace the spark arresting screen (not on catalytic mufflers); clean the carburetor area and the air filter. |
| Monthly | Clean the fuel tank and the outside of the carburetor; check the fuel lines for cracks and change if necessary; change the fuel filter in the tank; check cables and connections; replace the spark plug and change the air filter. |
Husqvarna says that if the machine is low on power, hard to start or runs poorly at idle, check the spark plug first, and that the plug should be replaced after about a month in operation or earlier if necessary. A dirty air filter, the wrong mix and poor fuel or oil are the causes it lists for plug deposits. Use the recommended plug, since the wrong type can damage the piston and cylinder.
Parts to buy for the Husqvarna 125B leaf blower
| Part | Part number | Notes |
|---|---|---|
| Air filter | 545112101 | Replaced by 597797901. |
| Spark plug | Champion RCJ-6Y | Gap 0.6 mm (0.024 in); RCJ-8Y is also listed. |
Husqvarna also sells a 125B and 125BVX blower tune-up kit with a fuel filter, air filter and spark plug.
1:50
Mix, Husqvarna oil
0.10 L per 5 L of gasoline. 1:33 with other oil.
0.6 mm
Plug gap
Champion RCJ-6Y or RCJ-8Y; replace monthly.
0.5 L
Fuel tank
Change the tank fuel filter monthly.
Husqvarna 125B leaf blower: questions
What fuel mix does a Husqvarna 125B use?
With Husqvarna two-stroke oil, the mix is 1:50, or 2 percent, which is 0.10 liter of oil per 5 liters of gasoline. If Husqvarna oil is not available, use another good-quality oil intended for air-cooled engines at 1:33, or 3 percent, which is 0.15 liter per 5 liters.
What spark plug does a Husqvarna 125B use?
The manual names a Champion RCJ-6Y in its technical data and a resistor plug Champion RCJ-8Y or equivalent in its maintenance section. The gap is 0.6 millimeter in both places. Because the two differ, check your engine’s label or ask a Husqvarna dealer, and never use a different plug type.
How often should I replace the spark plug on a Husqvarna 125B?
Husqvarna says the plug should be replaced after about a month in operation, or earlier if necessary, and its monthly list includes replacing it. Weekly, clean the outside of the plug and check the gap. If the blower is low on power, hard to start or runs poorly at idle, check the plug first.
How big is the fuel tank on a Husqvarna 125B?
0.5 liter. The engine is a 28 cc two-stroke with a 35 millimeter bore and 28.7 millimeter stroke, rated 0.8 kilowatt, and the blower idles at 2,800 to 3,200 RPM. Maximum speed is 8,600 RPM blowing, and 7,500 RPM vacuuming on the BX and BVX models.
When do I change the fuel filter on a Husqvarna 125B?
Monthly. Husqvarna’s monthly list includes changing the fuel filter in the fuel tank, cleaning the fuel tank, and checking the fuel lines for cracks or other damage and changing them if necessary. A clogged filter is a common reason a two-stroke blower loses power or stalls.
How do I clean the air filter on a Husqvarna 125B?
Remove the air filter cover and take out the filter. Husqvarna says it should be cleaned regularly, and a filter that has been used for a long time cannot be completely cleaned and must be replaced. A damaged air filter must be replaced.
Clean it daily, and change it monthly.
Why does my Husqvarna 125B spark plug keep fouling?
Husqvarna lists four causes of deposits on the plug electrodes: incorrect carburetor adjustment, an incorrect fuel mixture with too much oil or the wrong type, poor quality gasoline or oil, and a dirty air filter. Correct the mix first, since that is the easiest to check and to get wrong.
What is the difference between the 125B and the 125BX and 125BVX?
All three use the same 28 cc engine. The BX and BVX series add vacuuming with a collection bag, so their daily checks include the inlet cover lock, a clean fan impeller and an intact bag. They weigh 4.4 kilograms against 4.3.
What oil should I never use in a Husqvarna 125B?
Husqvarna says never to use two-stroke oil made for water-cooled outboard engines, sometimes called outboard oil, and never to use oil intended for four-stroke engines. Use its own two-stroke oil, or a good-quality oil intended for air-cooled two-stroke engines.
Does a Husqvarna 125B have a spark arrester?
The engine has a catalytic converter muffler. The weekly list says to clean or replace the spark arresting screen, but adds that this does not apply on mufflers with a catalytic converter. Check the muffler on your model, and keep the cooling fins and the air intake at the starter clear.
How much does a Husqvarna 125B weigh?
4.3 kilograms without fuel, with the blower tube and standard nozzle fitted. The 125BX and 125BVX weigh 4.4 kilograms. Husqvarna lists the sound power level as 106 decibels measured and 107 guaranteed for each of the three.
Where do I mix the fuel for a Husqvarna 125B?
In a clean container intended for fuel, and never in the blower’s tank. Husqvarna warns to shut the engine off before refuelling, let it cool for a few minutes, open the fuel cap slowly and tighten the cap securely, and move the machine away from the refuelling area before starting.
What is the Husqvarna 125B air filter part number?
Husqvarna 545112101 is the air filter for the 125B, 125BX and 125BVX, and it has been replaced by 597797901. Husqvarna also sells a tune-up kit for the 125B and 125BVX with a fuel filter, an air filter and a spark plug.