Chainsaw Too Much Compression: Causes, Solutions and Tips

Chainsaw Too Much Compression: Causes, Solutions and Tips

As an avid chainsaw user, keeping my equipment in top working order is essential. A common issue that can crop up is too much compression, which can lead to a host of problems if left unchecked. In this post, I’ll explore the causes of too much compression in chainsaws and how to fix it. Proper maintenance is key to avoiding compression problems, so I’ll also share my best tips on keeping your chainsaw running smoothly. Stick with me to learn how to troubleshoot compression problems and keep your chainsaw operating safely and efficiently for years to come.

Chainsaw Too Much Compression: Causes and Solutions

Chainsaw Too Much Compression: Causes, Solutions and Tips

When your chainsaw has too much compression, it makes the pull cord extremely difficult to yank. The decompression valve may even pop out when you try to start it up. High compression can lead to unpredictable performance and potentially hazardous chain breakage if left unaddressed. But what causes this excess compression in the first place? And how can you fix it?

What Causes Too Much Compression in Chainsaws?

Several issues can cause a buildup of compression inside your chainsaw’s cylinder and piston:

  • Carbon buildup from combustion byproducts creates friction and reduces space. This added resistance leads to excessive compression.
  • A worn needle bearing allows the crankshaft to tilt, reducing clearance. This added friction leads to high compression.
  • An overused starter spring lacks the strength to spin the engine fast enough to start properly. The slower rotation causes compression to increase.
  • Oil in the starter system seeps past seals and creates drag that makes the engine harder to turn over.
  • Old or bad fuel can leave behind deposits that increase resistance and compression.

How to Fix Chainsaw Too Much Compression

To reduce high compression in your chainsaw, you’ll need to address the underlying cause:

  • Use degreasers and wire brushes to meticulously clean the cylinder and piston of carbon deposits. This restores the proper clearances.
  • Inspect the needle bearing for wear and replace it if needed. This realigns the crankshaft and reduces friction.
  • Check the starter spring and replace it if excessively stretched or worn out. The new spring will spin the engine faster.
  • Drain oil from the starter housing and fix any leaks allowing oil to contaminate the starter system. This eliminates drag.
  • Drain old gas and debris from the fuel system. Refill with fresh fuel to dissolve deposits and dilute oil.

With the source of the high compression fixed, your chainsaw should turn over easier and operate smoothly. But proper maintenance is crucial for avoiding compression problems in the first place.

Chainsaw Compression Maintenance Tips

While you can’t avoid normal chainsaw wear and tear entirely, keeping your equipment well maintained goes a long way. Here are my top tips for minimizing chainsaw compression issues through proper care and upkeep:

Regularly Clean the Chainsaw

Over time, sawdust, dirt, and debris inevitably accumulate both inside and outside the chainsaw. I make a habit of periodic deep cleaning sessions to remove built up grime before it can cause problems. Scrub exterior surfaces with degreasers and use compressed air to blow out dust. Remove spark plug to clean the cylinder and piston of carbon. A clean chainsaw runs cooler and experiences less friction and drag leading to compression troubles.

Proper Fuel and Oil Management

Always use fresh 89 octane fuel blended with quality 2-stroke engine oil. Stale gasoline left sitting in your saws fuel system can lead to gummed up carburetors and sticky piston rings. This makes the engine harder to turn over, increasing compression. I never let gas sit for more than 2-3 weeks before draining the system and refilling with new fuel/oil mix. Proper fuel storage and management prevents deposits that boost compression.

Inspect and Replace Worn Parts

With heavy chainsaw use, parts like the starter spring, needle bearing, piston rings, and spark plug slowly degrade over time. I do a thorough inspection of these wear-prone components every 25 hours of chainsaw use. It’s simple to spot a stretched spring or chipped bearing once you know what to look for. Replacing worn parts before they fail keeps the engine running smoothly and prevent excess compression.

Proper Storage and Care

How you store and handle your chainsaw also impacts how well it operates. Let the engine fully cool before putting it away, and avoid setting it directly on the ground which can allow dirt inside. Always loosen guide bar nuts and release chain tension when storing. Keep the chain sharp and properly lubricated, and filter dust from the exterior. With proper care and storage, your chainsaw will have a long and healthy life free of compression issues.

Troubleshooting Chainsaw Compression Issues

Sometimes despite your best preventive maintenance efforts, chainsaw compression problems still crop up. Here’s how to troubleshoot and gauge whether you have low or high compression issues in your saw:

Signs of Low Compression

  • Difficulty starting – Requires many pulls to turn over the engine.
  • Rough idle – RPMs surge up and down and the engine sounds uneven.
  • Lack of power – Saw bogging down during cuts indicates low cylinder pressure.

Low compression usually indicates worn piston rings or leaking valves that reduce sealing. This allows compression to leak past the gaps.

Signs of High Compression

  • Difficulty pulling the starter rope – Excess resistance makes the pull cord very hard to yank.
  • Decomp valve popping out – Pressure building in the cylinder pushes the valve up.

High compression is typically caused by carbon buildup, contaminated fuel, or worn bearings increasing friction.

How to Test Chainsaw Compression

Using a compression gauge is the best way to accurately measure compression. First, remove the spark plug and thread the gauge into the spark plug hole. Then pull the starter cord several times while observing the gauge reading. Compare your measurements to the manufacturers recommended PSI, usually between 110-160 PSI. Significant deviations indicate compression problems needing repair.


Proper chainsaw maintenance and compression troubleshooting allows you to identify issues before they become dangerous. Regular cleaning, replacing worn parts, using fresh fuel, and proper storage and handling will minimize problems. But even well maintained saws can experience compression issues over time. By recognizing symptoms and properly testing compression, you can fix problems promptly and keep your chainsaw running safely and efficiently. With this knowledge, you’ll be confident handling any chainsaw compression problems encountered.

Frequently Asked Questions

How much compression should a chainsaw have?

Most chainsaws require 110-160 PSI of compression for proper operation. Always compare your measurements to the manufacturer’s specifications. Significant deviation from the recommended range indicates a compression problem.

Can a bad spark plug cause too much compression?

Yes, a faulty spark plug can contribute to high compression. Spark plugs create drag that makes the engine harder to turn over if excessively worn or fouled with deposits. Replacing worn plugs restores proper clearances.

How can I increase the compression on my chainsaw?

If diagnosed with low compression, inspect and replace worn piston rings and valves. This restores the cylinder’s sealing properties to contain compression. Also replace fouled spark plugs to minimize drag during ignition.

What are the dangers of too much compression in chainsaws?

Excess compression puts dangerous stress on chainsaw components. This can lead to unpredictable chain acceleration or breakage resulting in injuries and amputations. Keep compression within manufacturer specifications.

How often should I service my chainsaw to avoid compression issues?

It’s recommended to do complete service and inspection of your chainsaw every 15 hours of use. This allows you to spot worn parts and prevent large compression deviations before they become problematic.

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