How to inspect a used Stihl RM 448 T — UK guide
The Stihl RM 448 T is the German premium-mid self-propelled petrol mower in the UK. Built to a noticeably higher build standard than the Mountfield equivalent, but it commands a premium used as well as new. Here is the 10-minute inspection that catches every fault buyers regret missing.
Before you go
Bring: spark-plug socket (16mm), a torch, and a small magnet (to test the deck for filler-and-paint repairs).
Insist on a cold start. A Stihl mower that has been started 5 minutes before you arrived will hide carburettor problems.
1. Cold-start the Stihl-Kohler engine
Two primer squeezes, then a single firm pull. A healthy RM 448 T fires on the first pull cold and idles within 5 seconds without smoke.
Smoke that clears in 10 seconds is normal on a cold start. Persistent smoke means top-end wear — walk away unless dirt-cheap.
Knocking or rattling once running means internal damage. Replacement Stihl-Kohler block is £400+, so the mower is effectively scrap.
2. Test the single-lever drive
Engage the bail-arm and walk the mower onto an incline. The single-lever drive should pull cleanly without slipping or hesitating.
Slipping under load = stretched drive belt. £35 OEM part, 45-minute DIY job. Knock £50 off the asking price.
Drive that locks fully on = the drive cable has stretched and lost its return travel. £18 OEM cable, same DIY job. Knock £25 off.
3. Inspect the steel deck
Lift the front of the mower and shine your torch underneath. Surface rust is normal at any age and harmless. Stihl decks are powder-coated steel and reasonably durable.
Daylight visible through the deck means rust-through — walk away unless under £100. Replacement decks are not economically available.
Magnetic check on patches: the small magnet sticks to genuine steel but not to filler. If the magnet does not grab on a suspect area, the deck has been repaired and the mower has been through a serious impact.
4. Test the operator-presence bar and brake
Release the operator-presence bar with the engine running. The blade should stop within 3 seconds.
Blade keeps spinning past 5 seconds = the brake disc is worn. £25 OEM part, but flag it. Knock £40 off and budget the fix.
Bar feels notchy or stiff = the cable is corroded inside the sheath. £15 OEM cable, easy DIY swap.
5. What it's worth in 2026
2018–2020: £180–£280 in tidy condition with documented service.
2021–2023: £300–£420. Newer engine spec, less likely to need carb work.
2024–2025: £450–£540. Near-new, sometimes with dealer warranty remaining.
Knock £40 for: stretched drive cable, missing service stamps, worn operator-presence bar. Knock £100 for any deck filler repair or evidence of drop damage.
FAQs
Is the Stihl RM 448 T worth the premium over the SP46?
Yes, if you keep mowers for 10+ years. The Stihl deck stamping is genuinely heavier-gauge, the engine bearings are better-spec, and the resale curve is shallower. For 5-year ownership, the Mountfield SP46 is the smarter buy on cost-per-year terms.
What does a Stihl-dealer service cost?
£95–£140 including oil, plug, air filter, blade sharpen and carb clean. Worth booking on first purchase to baseline the mower, then DIY annually for under £25.
Where can I buy genuine Stihl parts?
Any authorised Stihl dealer — find the nearest via the Stihl GB website. Online parts are available but the dealer network is the strongest of any garden-machinery brand, so use it.
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