ECHO CS-310 chain fit, 50:1 fuel and service checks
Match the ECHO CS-310’s installed bar and chain before ordering a loop. The cited manual lists 12-, 14- and 16-inch combinations using 45, 52 and 57 drive links, respectively. ECHO’s 91PX chain has low-profile 3/8-inch pitch and 0.050-inch gauge.
Bar oil and the 50:1 two-stroke fuel mixture fill separate systems.
Bar length alone cannot identify a loop
| Nominal bar | Bar identity | Drive links |
|---|---|---|
| 12 in | 12A0CD3745 | 45 |
| 14 in | 14A0CD3752 | 52 |
| 16 in | 16A0CD3757 | 57 |
Ordinary 3/8-inch chain is not identified by that same full specification. Check the bar stamp, sprocket compatibility and drive-link count together before fitting a replacement.
The listed14-to 16-inch change adds five drive links, while12 to 14adds seven. That illustrates why a rule such as “add the same number of links per two inches” cannot replace the specified combination. A different replacement bar can also change the required count.
One oil lubricates the engine; another lubricates the chain
The CS-310 operator manual specifies 50:1 gasoline/two-stroke oil, 89-octane minimum fuel and the required air-cooled oil standards. Bar-and-chain oil goes in the separate oiler tank. Neither straight gasoline nor bar oil is a substitute for the engine’s premixed fuel.
For a 1.25Lgasoline batch at 50:1, measure25 ml of the specified two-stroke oil into an approved mixing container. Mix there according to the manual, label the container, and avoid creating an unmeasured ratio by topping fuel and oil separately inside the saw.
Inspect after refueling, service with the engine stopped
Inspect chain condition, tension, lubrication, fuel leakage and the bar/sprocket as directed before work and during refueling checks. Stop the engine and disconnect its plug lead for maintenance. A chain brake reduces a hazard; it does not make a damaged or mismatched cutting attachment acceptable.
The cited CS-310 manual specifies BPMR8Y at 0.65 mm. Use the correct manual for the serial and market. EPA’s E15 guidance excludes gasoline lawnmowers and chainsaws from E15use; a pump’s higher vehicle-compatible blend is not permission to use it in this saw.
Echo CS-310 chainsaw: fuel mix, spark plug, chain and maintenance schedule
The ECHO CS-310 chainsaw runs on a 50:1 gasoline and two-stroke oil mix, which is 2.6 fluid ounces of oil per US gallon, using 89 octane fuel with no more than 10% ethanol and JASO FD oil. The spark plug is an NGK BPMR8Y gapped 0.65 millimeter. It takes 3/8 inch pitch chain on 12, 14 or 16 inch bars, with 45, 52 or 57 links.
The chain oil tank holds 260 millilitres, and ECHO grades its maintenance tasks by difficulty.
Stop the engine and remove the spark plug lead before any maintenance, since a saw with a momentary stop switch can start unintentionally. Never refuel a hot or running saw, and never fill fuel indoors.
A 30.5 mL two-stroke saw: the mix, the plug and the chain
The ECHO CS-310 is a homeowner chainsaw with a 30.5 millilitre (1.86 cubic inch) air-cooled two-stroke engine, an automatic oiler and an 8.8 pound dry weight without bar and chain. As a two-stroke it runs on a mix of gasoline and oil, so unlike the four-stroke engines on this section it has no sump to fill. What it has instead are two tanks, and each one has its own product.
| Item | Specification |
|---|---|
| Engine | Air-cooled two-stroke single cylinder, 30.5 mL (1.86 cu in); bore 36.0 mm, stroke 30.0 mm; compression ratio 6.7:1 |
| Fuel to oil ratio | 50:1 |
| Gasoline | 89 octane unleaded; no methyl alcohol, no more than 10% ethyl alcohol or 15% MTBE; no E15 or E85 |
| Two-stroke oil | ISO-L-EGD (ISO/CD 13738) and JASO M345-FD air-cooled two-stroke oil |
| Fuel tank | 250 mL (8.45 US fl oz) |
| Spark plug | NGK BPMR8Y |
| Spark plug gap | 0.65 mm (0.026 in); tighten to 13 to 17 N·m (110 to 150 lbf·in) |
| Chain oil tank | 260 mL (8.8 US fl oz), automatic oiler |
| Bar and chain oil | High-quality bar and chain oil: SAE 30 in summer, SAE 10 in winter or when cutting resinous trees |
| Idle speed | 3,200 RPM |
| Sprocket | Spur type, 6 tooth, 3/8 in pitch |
| Gasoline | Two-stroke oil |
|---|---|
| 1 US gallon | 2.6 fl oz |
| 2 US gallons | 5.2 fl oz |
| 5 US gallons | 13 fl oz |
| 5 liters | 100 cc |
| 10 liters | 200 cc |
| 25 liters | 500 cc |
ECHO’s method is to put half the gasoline in an approved can, add the oil, close it and shake, then add the rest and shake again. Label the can as two-stroke mix.
ECHO’s manual adds that its own two-stroke oils may be mixed at 50:1 in all ECHO engines sold in the past, regardless of the ratio in older manuals. The fuel mix calculator does the sum for other batch sizes.
The bar and chain the manual lists
| Guide bar length | Part number | Chain |
|---|---|---|
| 305 mm (12 in) | 12A0CD3745 | 3/8 in pitch, type 91PX or 91VG, 45 links |
| 356 mm (14 in) | 14A0CD3752 | 3/8 in pitch, type 91PX or 91VG, 52 links |
| 406 mm (16 in) | 16A0CD3757 | 3/8 in pitch, type 91PX or 91VG, 57 links |
The manual warns that a replacement chain or bar other than those listed, or use without the optional kick guard in place, may cause severe kickback. The chain and bar gauge must be the same.
The maintenance intervals, and who does what
| When | What |
|---|---|
| Daily or before use | Inspect and clean the air filter; inspect and adjust the automatic oiler; inspect the oil filter and fuel system; inspect and clean the bar and sprocket nose; inspect, sharpen and tension the chain; inspect the sprocket, cooling system, recoil rope and fasteners. |
| Every refuel | Inspect the fuel system and the guide bar and sprocket nose. |
| Every 3 months | Replace the air filter; inspect and replace the oil filter; inspect the fuel filter and fuel cap gasket; inspect, clean or replace the spark plug and the muffler spark arrester. |
| Yearly | Inspect and replace the fuel filter, and replace the fuel cap gasket. |
ECHO grades each task from level 1, easy with common tools, to level 3, see your dealer. Most of the list above is level 1, and cleaning the cooling system, the sprocket and the spark arrester are level 2. For storage the manual says to run the tank and carburetor dry and, with the plug out, pour 7 cc (0.25 ounce) of fresh two-stroke oil into the cylinder.
50:1
Fuel to oil
2.6 fl oz of oil per US gallon of gasoline.
0.65 mm
Spark plug gap
NGK BPMR8Y, tightened to 13 to 17 N·m.
3/8 in
Chain pitch
On 12, 14 and 16 inch bars, 45, 52 and 57 links.
Echo CS-310 chainsaw: questions
What is the fuel mix for an Echo CS-310?
50:1, gasoline to two-stroke oil. That is 2.6 fluid ounces of oil per US gallon of gasoline, 5.2 ounces for 2 gallons and 13 ounces for 5 gallons, or 100 cc of oil for 5 liters. Use ISO-L-EGD and JASO FD two-stroke air-cooled engine oil.
What gasoline should I use in the CS-310?
89 octane unleaded, with no methyl alcohol, no more than 10% ethyl alcohol and no more than 15% MTBE. Do not use E15 or E85. Mix fresh fuel in an approved container marked as two-stroke mix, and empty the tank before storage.
What spark plug does the Echo CS-310 use?
An NGK BPMR8Y with a gap of 0.65 mm (0.026 inch). Tighten it to 13 to 17 N·m (110 to 150 lbf·in). ECHO lists inspecting, cleaning or replacing the plug every 3 months.
What bar and chain does the CS-310 take?
A 12, 14 or 16 inch low-kickback bar with 3/8 inch pitch chain, type 91PX or 91VG, of 45, 52 or 57 links. ECHO lists bar part numbers 12A0CD3745, 14A0CD3752 and 16A0CD3757. The chain and bar gauge must match.
How much bar and chain oil does the CS-310 hold?
260 millilitres (8.8 US fluid ounces), fed by an automatic oiler. Use high-quality bar and chain oil, SAE 30 in summer and SAE 10 in winter or when cutting resinous trees, and refill it whenever you refuel.
How big is the CS-310 fuel tank?
250 millilitres (8.45 US fluid ounces). Because the tank and the chain oil tank are nearly the same size, ECHO’s manual says to refill the chain oil when you refuel.
How often should I replace the air filter on the CS-310?
Inspect and clean it daily or before use, and replace it every 3 months. ECHO notes that the time intervals shown are maximum, and that actual use decides the frequency. Replacement is recommended when you find damage or wear.
How do I store an Echo CS-310?
Drain the fuel tank, press the purge bulb six or seven times, and run the engine until it stops. Let it cool, remove the plug and pour 7 cc (0.25 ounce) of fresh two-stroke oil into the cylinder. Store it dry, away from fuel fumes.
How big is the CS-310 engine?
30.5 millilitres (1.86 cubic inches), air-cooled, two-stroke and single-cylinder, with a 36.0 mm bore, a 30.0 mm stroke and a 6.7:1 compression ratio. The idle speed is 3,200 RPM and the dry weight is 4.0 kg (8.8 pounds) without bar and chain.
Which Echo CS-310 maintenance jobs are easy?
ECHO grades each task. Level 1 is easy with common tools, and most of the list, including the air filter, fuel filter, spark plug and fasteners, is level 1. Level 2 needs some specialized tools and covers the chain, sprocket, cooling system and spark arrester.
Can I use a longer bar on the CS-310?
Not beyond those the manual lists. ECHO says a replacement chain or bar other than those specified, or use without the optional kick guard in place, may cause severe kickback. Stay with 12, 14 or 16 inch bars.
What is the spark arrester on the CS-310 for?
The muffler carries a spark arrester screen that stops sparks leaving the exhaust. ECHO lists inspecting, cleaning or replacing it every 3 months, and a clogged one loses power. Use only emission components designed for the unit.