STIHL MS 251 C-BE
The STIHL MS 251 C-BE is a powerful and efficient homeowner chainsaw designed for cutting firewood, felling small to medium trees, and general property maintenance. With its 45.6 cc engine producing about 2.95 horsepower and weighing roughly 11.9 pounds, it delivers an excellent balance of cutting power and maneuverability. The saw works best with a 16″ to 18″ guide bar and is ideal for handling wood in the 6″ to 20″ diameter range, making it perfect for typical yard trees, storm cleanup, and routine firewood processing. The “C-BE” designation means it comes equipped with STIHL’s Easy2Start™ system and Quick Chain Adjuster, which make starting and maintaining the saw simple and tool-free. To achieve the best efficiency, always use fresh 50:1 fuel mixture with quality 2-cycle oil and proper bar-and-chain lubricant, keeping the oil reservoir filled so the chain stays cool and well-oiled. Ensure the chain is sharp and correctly tensioned—too tight strains the motor, while too loose can derail the chain. Let the saw do the work rather than forcing it; use the bumper spikes to stabilize your cuts and allow the chain to reach full speed before contacting wood for cleaner, faster cuts. After use, clean debris from the air filter, bar groove, and sprocket area, and store the saw in a dry place with the scabbard on. For troubleshooting, if the saw won’t start, check that the chain brake is off, the choke lever is in the proper position, and the spark plug is clean; if the chain isn’t oiling, make sure the bar oil tank is full and the oil ports aren’t clogged. A dull or binding chain often means it needs sharpening or tension adjustment, and loss of power usually points to a dirty air filter or stale fuel. When properly maintained, the MS 251 C-BE offers years of reliable use with up to 20% less fuel consumption and 50% fewer emissions than older models, making it one of the most efficient and user-friendly saws in the homeowner lineup.
Size & capability overview
What size work is it well suited for?
- Engine displacement: 45.6 cc.
- Engine power: approximately 2.2 kW (≈ 2.95 bhp) for the “occasion use” spec.
- Powerhead weight: about 11.9 lbs. (5.3 kg) for the machine without bar & chain.
- Recommended guide bar lengths: 16″–18″ (40–45 cm) for optimal performance.
- Typical standard configuration: 18″ bar, .325″ RM3 chain.
- Intended use: Homeowner / occasional use (pruning, felling small trees, firewood).
What that means practically:
- You can comfortably use it to fell small to medium trees, especially those with diameter perhaps in the ~6″–20″ range (depending on your strength and support).
- It's very good for cutting firewood, trimming branches, thinning out limbs, and general homeowner yard/tree work.
- It is not really built for heavy-commercial work or large timber (e.g., massive logs, full-scale logging) if you regularly cut very large trees (> 20″ diameter) you might want a bigger saw.
- Because it's lighter, you'll get less operator fatigue compared to a heavier pro saw.
Efficiency factors:
- It features “Easy2Start™ which reduces effort when pulling the starter cord.
- Quick Chain Adjuster (QCA) allows tool-free tensioning of the chain.
- Fuel savings: up to ~20% less fuel and ~50% fewer emissions compared to older models (per the manufacturer).
Best‐practice usage for efficiency & longevity
To get the most out of your MS 251 C-BE and keep it running smoothly, follow these best practices:
- Fuel & oil mixture / correct fluids
- Use high-octane unleaded gasoline (minimum recommended) mixed with 2-cycle oil at the correct ratio (STIHL recommends 50:1 for many of their 2-cycle saws) per their guide.
- Use proper chain/bar oil in the chain-oiler reservoir; check regularly that oil is flowing.
- Always check the fuel cap area is clean so no debris falls into the tank when refueling.
- Check chain tension & sharpness
- Use the Quick Chain Adjuster (“B” in model code) to keep chain tension correct— a loose chain slows cutting, a too-tight chain causes extra wear.
- Keep the chain sharp: dull cutters make the saw work harder, waste fuel, increase vibration, and increase risk of kickbacks. STIHL provides a guide for sharpening their saw chains.
- Inspect the guide bar groove, rails, and chain sprocket regularly to reduce wear.
- Pre-cut checks & safe setup
- Before each job, inspect the area: make sure your workspace is clear, you have an escape path, ensure no one enters your danger zone. (See STIHL’s start-up safety guide)
- Engage the chain brake when starting or moving the saw to avoid accidental chain movement.
- Ensure the bar, chain and sprocket are correctly mounted. Refer to the manual section “Mounting the Bar and Chain”.
- Cutting technique for efficiency
- Let the saw do the work— don’t force it. Pushing too hard slows things down and increases wear.
- Use the bumper spikes (“dog”-spikes) properly to steady the bar when cutting through logs. Ensures smoother cuts and less strain.
- Use the correct bar length for the job: using an 18″ bar on small logs is okay, but if you often cut just small limbs, you might use a shorter bar (if compatible) to reduce weight and increase maneuverability.
- After each cut, let the chain free spin after throttle release so lubrication fully coats the bar before next cut.
- After-use & storage care
- Clean the saw after use: remove debris from cooling fins, air intake, sprocket cover and chain area.
- When storing for an extended period, consider running the saw until the fuel mixture is used up to avoid carburetor membrane sticking.
- Store in a dry place, with the scabbard protecting the bar/chain.
Easy Troubleshooting Tips
Here are common issues and how to address them quickly:
| Issue | Possible cause | Quick fix |
|---|
| Saw won't start or hard to start | Chain brake engaged, choke/starting lever not set, fuel mixture wrong, spark plug fouled | Ensure chain brake is off, follow correct cold/start sequence (see STIHL guide). Check fuel mix (50:1), inspect spark plug. |
| Chain not lubricating / no oil on bar | Chain oil reservoir empty, oil passage blocked, bar groove dirty | Fill chain-oil tank, clean bar groove and oil inlet, check that oil flows when running saw. |
| Chain keeps binding or the saw slows dramatically | Chain too tight, chain dull, guide bar worn or damaged, incorrect bar size | Loosen chain tension, sharpen or replace chain, inspect guide bar for wear/burrs. |
| Excessive vibration or rough running | Engine mount or anti-vibration system worn, chain imbalance, bar damage | Inspect mounts and anti-vibration rubber, ensure chain and bar are in good condition and balanced. |
| Saw stalls under load | Air filter clogged, carburetor not tuned, fuel mixture incorrect | Clean/replace air filter, check carburetor settings (if accessible), ensure fresh fuel mixture. |
| Bar or chain gets hot/discolored quickly | Inadequate lubrication, chain too tight, dull chain, cutting too aggressively | Ensure proper oiling, check tension, sharpen chain, cut with proper technique. |
Summary
The MS 251 C-BE is a very capable homeowner chainsaw: good power (45.6 cc), suitable for 16″–18″ bar length (and recommended for that range) for tasks like small tree felling, firewood cutting, pruning and thinning. For best efficiency use it with proper fuel/oil, keep the chain sharp and properly tensioned, use good cutting technique, and maintain it regularly. Many issues are avoidable if you follow the simple checks above.
