Stihl MS 170 Saw Chain Sizing (Fitment Chart)
For a common STIHL MS 170 setup, the chain is 3/8-inch Picco pitch, .043-inch (1.1 mm) gauge: 44 drive links for a 12-inch bar, 50 for 14 inches, or 55 for 16 inches. Check the markings on your actual bar and saw manual before buying; bar length alone does not confirm fit.
“A useful shop rule is: the bar, not the engine size, decides which chain fits.” I use that check first because an MS 170 can have different bar setups, and a replacement bar or sprocket may change the required chain. Match three details before you head out: pitch, gauge, and drive-link count.
MS 170 chain fitment chart
This chart covers common MS 170 combinations using 3/8-inch Picco pitch and .043-inch (1.1 mm) gauge. It is a starting point, not a substitute for the markings on your installed bar. Check all three measurements before ordering or fitting a chain.
| Bar length | Common pitch | Common gauge | Drive links |
|---|---|---|---|
| 12 in / 30 cm | 3/8″ Picco (3/8″P) | .043″ / 1.1 mm | 44 |
| 14 in / 35 cm | 3/8″ Picco (3/8″P) | .043″ / 1.1 mm | 50 |
| 16 in / 40 cm | 3/8″ Picco (3/8″P) | .043″ / 1.1 mm | 55 |
Drive links are the small teeth along the bottom of the chain that sit in the bar groove and engage the sprocket. Count them when a bar marking is missing or unclear. These counts apply to the pitch and gauge shown; a different bar or sprocket can change what fits.
How to read the bar markings
Bar markings identify the chain size the bar is designed to accept. Look near the bar’s mounting end or on its side for pitch, gauge, and sometimes the required number of drive links. Markings can be worn, hidden by sawdust, or formatted differently by maker.
Wipe the bar clean and inspect both sides. You may see “3/8P,” “1.1 mm,” or a bar part number rather than every measurement. If the markings are missing, use the bar’s part number to check its maker’s specifications; do not guess based on its length.
What the three measurements mean
Pitch is the spacing between the chain’s rivets, measured using the chain maker’s method. Gauge is the thickness of the drive links where they fit into the bar groove. Drive-link count is the total number of those links around the chain. All three must match the installed bar and compatible drive sprocket.
A chain with the wrong gauge may not sit correctly in the groove. A pitch mismatch can prevent the chain from engaging the sprocket as designed. Too many or too few drive links will also prevent correct fitment, even if the bar length looks right.
Confirm the setup before buying
Confirming the bar and sprocket specifications avoids buying a chain that looks right but will not run correctly. The MS 170 is about 30.1 cm³, but displacement does not determine chain size. Use the installed parts and the model-specific manual to verify the correct combination.
Check the bar, sprocket, and manual
- Stop the saw. Engage the chain brake, shut off the engine, and let the saw cool. Remove the spark-plug boot before maintenance, following the manual.
- Read the bar. Find the pitch and gauge markings, then note the bar length and any drive-link count.
- Check the sprocket. Its pitch must match the chain. If the sprocket has been changed, confirm that it is approved for the saw and matches the bar and chain.
- Compare with the manual. Check the manual for your saw version and market. If parts or markings do not agree, identify the bar and sprocket by their part numbers before ordering.
Do not combine measurements from different setups. For example, a 14-inch bar does not automatically take a 50-link chain if it has a different pitch, gauge, or sprocket arrangement.
Common fitment situations
These examples show how to use the chart; they are not reports of specific customer repairs. The goal is to match the components already on the saw, not to assume every MS 170 has the same bar.
| Situation | What to check | Next step |
|---|---|---|
| Marked 12-inch bar | 3/8″P, .043″ / 1.1 mm | If markings and manual agree, use the 44-link option |
| Marked 14-inch bar | 3/8″P, .043″ / 1.1 mm | If markings and manual agree, use the 50-link option |
| Marked 16-inch bar | 3/8″P, .043″ / 1.1 mm | If markings and manual agree, use the 55-link option |
| Bar has different pitch or gauge | Bar and sprocket specifications | Find the approved matching chain; do not use the chart above |
| Markings are unreadable | Bar and sprocket part numbers | Verify specifications with the maker or a STIHL dealer |
A common mistake is to order by bar length alone. Another is to trust the old chain without checking it: the saw may have received a replacement bar or sprocket since the original setup. If the chain size cannot be confirmed, pause rather than forcing a near match.
Fit and tension the replacement chain
Correct fit means the chain matches the bar and sprocket and moves freely when adjusted. Before fitting, wear eye protection and gloves, keep the engine off, and remove the spark-plug boot as directed by the manual. Never work on a chain while the saw can start.
Install the chain in the right direction
Loosen the bar nuts and release chain tension according to the manual. Fit the chain around the sprocket and into the bar groove. On the top of the bar, the cutter edges must point forward, toward the bar nose. If they face backward, the chain is reversed and will not cut correctly.
Seat each drive link in the groove around the full bar. Refit the cover and adjust tension using the saw’s specified procedure. Do not use force to make a chain fit; a mismatch in pitch, gauge, or link count is a reason to stop and recheck the parts.
Set and recheck chain tension
A correctly tensioned chain stays engaged in the bar groove, while still moving by hand with gloves when the brake is released. Follow the tension check in your manual, since adjustment details can vary by saw version. Tighten the bar nuts as directed, then recheck tension.
New chains can settle during initial use. Stop the engine, engage the brake, and recheck tension as instructed. A hot chain expands; do not tighten it to the same tightness you would use for a cold chain, because it can become too tight as it cools. A loose or damaged chain should not be run.
Sharpening and setup checks
Sharpening details depend on the chain type, not just the saw model. A common 3/8″P chain may use a 4.0 mm (5/32-inch) round file, but confirm the chain maker’s instructions before filing. File angle and depth-gauge settings must also match the specific chain.
File size, angle, and depth gauges
The file size is the round file diameter used to shape the cutter. The filing angle is the angle across the cutter’s top plate. The depth gauge controls how much wood the cutter can take. For common 3/8″P chain, a 0.65 mm (0.026-inch) depth-gauge setting is a reference; verify it with the chain maker’s chart and correct tool.
| Item | Common reference for 3/8″P chain | Confirm before use |
|---|---|---|
| Round file | 4.0 mm / 5/32 in | Exact chain type and maker |
| Top-plate filing angle | Often 30° | Chain maker’s filing instructions |
| Depth-gauge setting | 0.65 mm / 0.026 in | Chain maker’s specification and proper tool |
These are common references, not a guarantee for every chain sold for an MS 170. Filing at the wrong size or angle can leave cutters uneven or cut poorly. Keep cutters even, use a filing guide if needed, and replace a chain with cracked, damaged, or excessively worn links.
Oil and operating checks
Fill the oil reservoir with bar-and-chain oil. Check oil delivery using the method in the manual; do not assume a universal flow rate or oil type beyond the product’s instructions. Also check fuel: STIHL specifies a 50:1 gasoline-to-STIHL two-stroke oil mix for the MS 170, using the fuel requirements in the manual. Do not use straight gasoline.
Start the saw according to the manual on firm ground, with the chain brake engaged. Check that the chain stops at idle and that lubrication reaches the chain before cutting. Keep two hands on the saw, avoid the upper bar nose, and do not cut above shoulder height. Contact with the nose can cause kickback.
Conclusion: make fitment a three-part check
For the common MS 170 setup, the quick chart is 44 links for 12 inches, 50 for 14 inches, and 55 for 16 inches, with 3/8″P pitch and .043-inch (1.1 mm) gauge. Treat those counts as conditional: confirm the markings on your bar, the sprocket pitch, and the manual before buying or installing a chain.
FAQs
What chain size does a STIHL MS 170 use?
A common setup uses 3/8-inch Picco pitch, .043-inch (1.1 mm) gauge. Confirm the actual bar and sprocket markings because setups can vary.
How many drive links does a 12-inch MS 170 chain have?
For the common 3/8″P, .043-inch setup, a 12-inch bar uses 44 drive links. Check your bar markings before ordering.
How many drive links does a 14-inch MS 170 chain have?
The common chart lists 50 drive links for a 14-inch bar with 3/8″P pitch and .043-inch gauge.
How many drive links does a 16-inch MS 170 chain have?
The common chart lists 55 drive links for a 16-inch bar with 3/8″P pitch and .043-inch gauge.
Can I choose a chain by bar length alone?
No. Match pitch, gauge, and drive-link count, and make sure the chain is compatible with the sprocket.
What does .043-inch gauge mean?
Gauge is the thickness of the chain’s drive links where they sit in the bar groove. The chain gauge must match the groove.
What file size is used for common 3/8″P chain?
A 4.0 mm (5/32-inch) round file is common, but check the exact chain maker’s sharpening instructions.
What fuel mix does the MS 170 use?
STIHL specifies a 50:1 gasoline-to-STIHL two-stroke oil mix. Follow the model manual’s fuel specifications.
Can I use a different pitch if the chain fits the bar?
No. The chain pitch must also match the drive sprocket. A mismatch can cause poor engagement and unsafe operation.
What should I do if the bar markings are unreadable?
Use the bar and sprocket part numbers to verify their specifications with the maker or a STIHL dealer. Do not guess from bar length.
(This article was written by one of our staff writers, David Hensley. Visit our Meet the Team page.)
