Stihl TS420 Parts: The 12 Things That Actually Wear Out
The Stihl TS420 is one of the best 14-inch concrete cut-off saws ever built. We've sold parts for them since the model came out, and over thousands of repairs we've learned that the same dozen components fail again and again. Here's the practical guide to keeping your TS420 alive — what wears out, why, and what part numbers to keep on the shelf.
1. Cooling Plate (Stihl P/N 0000 141 3200)
The cooling plate sits behind the cylinder and conducts heat away from the engine. It cracks from thermal cycling, especially if the saw runs lean or with a clogged air filter. Symptoms: power loss, overheating, hot exhaust. The old part number 4238 141 3200 was superseded by 0000 141 3200 — either will be cross-referenced. Replace whenever you do a top-end rebuild.
2. Impulse Hose (Stihl P/N 0000 141 8600)
The impulse hose connects the crankcase to the carburetor and provides the pulse signal that runs the fuel pump diaphragm. When it cracks or hardens with age, the saw runs lean (or won't start at all). It's the single most common cause of "the carb is bad" diagnoses that aren't actually a bad carb. Replace any time you smell fuel near the cylinder base or have unexplained no-starts.
3. Drive Belt — 14" Serpentine
The drive belt transfers engine power to the blade arbor. It wears at the V-grooves and stretches under continuous load. Replace every 100–200 hours of cutting time, or whenever you see glazing/cracking on the belt surface. We stock the OEM TS420/TS500 serpentine plus aftermarket equivalents.
4. Fuel Cap Assembly (Stihl P/N 0000 350 0514 for bayonet style)
The bayonet-style fuel cap on the TS420 has a vent o-ring that fails after a few hundred heat cycles. When it fails, fuel boils out (you'll smell gas) and the saw runs hot. The complete cap assembly includes the o-ring and rope. The older TS400 used a screw-style cap (0000 350 0517) which is a different part — make sure you're ordering for the right saw.
5. Water Kit Components
The water kit dust-suppression system on the TS420 has several wear points: - Banjo bolt, right side, long (0000 670 0206) — Cracks at the threads when over-tightened - Strainer with nut (0000 670 0400) — Clogs with sediment from job-site water - Pump barrel assembly (0000 670 6600) — Wears out the seals - Water hose (0000 937 4049) — UV degrades the outer jacket
If your water flow is inconsistent, start by replacing the strainer ($10) before assuming the pump is bad.
6. Fuel Filter (Stihl P/N 0000 350 3518 for TS700, similar for TS420)
The fuel filter (in-tank) clogs faster than most owners expect — especially in dusty Vegas conditions. Replace every 6 months or 50 hours of operation. Cheap insurance: at $9, replace it whenever you replace the spark plug.
7. Tank Vent (Stihl P/N 0000 350 5800)
The fuel tank needs to vent air in as fuel goes out. When the vent clogs, the tank goes into vacuum and the saw starves at full throttle. Symptoms: saw runs fine at idle, dies under load, restarts after sitting a minute. Replace with the OE Stihl vent — the aftermarket clones are hit or miss.
8. Air Filter Element
We don't list a specific part number because there are several variants depending on saw vintage and air-filter housing style — but the air filter is the single most-replaced part on any TS420 we see. In dusty Vegas concrete cutting, you should be cleaning or replacing it weekly. A clogged air filter is the #1 cause of running-rich symptoms (black smoke, lean carb adjustment).
9. Ignition Lead
The 10-meter ignition lead (Stihl 0000 930 2251, sold by the foot) chafes through where it routes over the cylinder. When it shorts to ground, you get intermittent miss or no spark. Easy field replacement.
10. Brass Shaft Sleeve (Stihl P/N 0000 708 4200)
The brass blade-shaft sleeve sits between the blade flange and the arbor. It's a sacrificial wear part that protects the more expensive arbor shaft. Replace any time you change the blade-side bearings, or whenever you notice blade wobble.
11. Hook-On Spring (Stihl P/N 0000 998 0604)
Small but critical — the hook-on springs that hold the air filter cover, fuel cap retainer, and various clamps fatigue over time. Keep a few spares in the toolbox.
12. Complete Rebuild Kit (T&L P/N TS420 KIT)
When your TS420 has more than ~800 hours of cutting time, individual repairs stop making economic sense. Our complete TS420 rebuild kit includes the piston/jug, full gasket set, crankshaft with bearings, fuel and air filters, decompression valve, drive belt, needle bearing, and spark plug — everything to bring a tired saw back to like-new operation. At ~$330, it's about half the cost of a new TS420 and a quarter the cost of taking it to an authorized service center.
Buying the right parts
Stihl's part-number system uses a 4-digit prefix and 8-digit base number (e.g., 0000 141 3200). Older parts may be referenced with hyphens (4238-141-3200) or spaces (4238 141 3200) — same part, same fitment. Supersession is common; the manual you have may reference an "old" number that's been replaced by a current one.
T&L Equipment stocks every part listed above in our North Las Vegas warehouse. Browse Stihl concrete saw parts, or call our parts counter at (702) 798-4149 with your saw's serial number for definitive fitment.
— Published by T&L Equipment, one of the Southwest's largest construction equipment parts sources. Serving Las Vegas contractors with over 13,600 in-stock parts since 1998.