Echo Trimmer Heads and What Fits What
The trimmer head is the part of an Echo that wears out in plain sight and still gets replaced later than it should. Eyelets go oval, the bump knob wears flat, the spool cracks where the line exits - and the machine keeps working badly for a whole season before anyone connects the two.
This page covers which head goes on which Echo, what the Speed-Feed design changes, and the fitment detail that catches most people out: the head and the adapter are not the same purchase.
Speed-Feed 400: what the number means
The Speed-Feed 400 is Echo part 99944200907, and it is the head most SRM owners end up on. The design difference is the reload: line feeds straight through the head and winds by turning the knob, without taking the spool out or opening anything. Anyone who has knelt in wet grass rewinding a conventional spool understands why this is the upgrade people actually make.
Echo lists it as fitting SRM series trimmers. The listing also carries a warning worth repeating: the head ships with no adapters. Echo shafts differ in thread and drive, so confirm what your machine needs before ordering - a head that arrives without the bolt and washer set it requires is a head you cannot fit that weekend.
Aftermarket copies of the Speed-Feed 400 are everywhere, and most list fitment across SRM-225, SRM-230, SRM-210 and SRM-250 as well as Shindaiwa T235 and T242. Shindaiwa sharing fitment is not a coincidence: both brands sit under the same parent company, and parts crossover between them is common.
When the head is the problem and when it is not
Three symptoms genuinely point at the head:
- Line snaps at the eyelet repeatedly. The eyelet has worn oval or sharp. Line will keep breaking at the same point no matter which brand you load.
- Bumping no longer feeds. The knob has worn down past the point where it can index the spool, or the spring has collapsed.
- Line welds itself inside the spool. Usually heat plus line that is too thick for the head, but a cracked spool wall lets coils cross and bind.
Two symptoms that look like head failure and are not: the engine bogging when line is at full length (that is a power or line-diameter issue, see trimmer line) and line unwinding all at once on start-up (usually wound the wrong direction).
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Fitment, in the order that matters
| Check | Why it matters |
|---|---|
| Shaft type - straight or curved | Curved-shaft machines take a different head and adapter set entirely |
| Thread and drive | The head bolts to the shaft; thread size is what actually decides fitment, not the model badge |
| Adapters included | The genuine Speed-Feed 400 ships without them. Aftermarket kits usually include a set |
| Line diameter rating | A head built for .095 in will bind on .105 in even though the line physically fits |
If you are replacing like for like, the fastest route is the number on the old head. If you are upgrading from a bump head to a Speed-Feed, the adapter question is the one to answer before ordering.
Genuine or aftermarket
Heads are one of the categories where the aftermarket is genuinely competitive. The mechanism is simple, the tolerances are not tight, and multi-packs cost a fraction of a single genuine head. What you give up is consistency: eyelet hardness varies between makers, and a soft eyelet wears oval in a season.
For a machine that works a few hours a month, an aftermarket head is a reasonable buy. For one that runs commercially, the genuine head lasts long enough that the price difference stops mattering.
Whichever you fit, the head only performs as well as what you load into it - see which trimmer line to run.
Frequently Asked Questions
What is the part number for the Echo Speed-Feed 400?
Will a Speed-Feed 400 fit an SRM-225?
Why does my trimmer line keep breaking at the head?
Can I put any trimmer head on an Echo?
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