Echo Carburettors: Fitment and When You Actually Need One

These groupings come from how aftermarket suppliers list fitment, which follows the engine rather than the badge. If your machine is not on a listing, the deciding factor is the engine, not the model name.

The PB-580 row is its own carburettor family entirely, separate from every trimmer engine above it - the rest of what wears on that blower, including the tube and filter, is on the blower parts page.

Two more groups sit outside the handheld trimmer range covered above. Echo's homeowner chainsaws - CS-370, CS-400, CS-400F and CS-420ES - run a Walbro WT-985 unit, covered on the CS-400 chainsaw parts page. And the small handheld blowers - PB-2100, ES-2100, PB-2155 and the rest of that group - run a Zama C1U-K42, detailed on the PB-2100 blower parts page.

A carburettor that is genuinely faulty is uncommon. A carburettor that cannot work because of something upstream is very common. In order:

1. Stale fuel. Pump petrol with ethanol goes off in weeks, not months, and leaves a varnish that blocks the tiny passages inside. This is the single biggest cause of two-stroke non-starts after winter.
2. Fuel lines and primer bulb. They perish. Hard, cracked lines suck air instead of fuel, and a split bulb cannot prime. Both are a few dollars and both are usually sold together in a tune-up kit.
3. Fuel filter in the tank. The weight on the end of the pickup line clogs and starves the engine under load - runs at idle, dies on the throttle.
4. Air filter. A blocked filter mimics a rich carburettor exactly. See air filters and tune-up parts.

If all four are good and it still will not hold a tune, then the carburettor is a fair suspect.

The genuine primer bulb number - and the generation split that catches people buying the wrong one - is on the Echo primer bulb page. A good spark but no start points at the plug rather than the carburettor - see the Echo spark plug page for the numbers by engine family.

The genuine in-tank fuel filter number for this family - and the older generation that takes a different one - is on the Echo fuel filter page.

A carburettor gummed up by old fuel usually recovers. The job is removing it, splitting it, soaking the body in carburettor cleaner, blowing the passages through with compressed air and fitting a new gasket and diaphragm set. Diaphragms harden with age and are the part that most often does not recover, which is why a rebuild kit costs a fraction of a carburettor and fixes a good share of cases.

Replacement makes sense when the body is corroded, the adjustment screws are stripped, or the machine is worth less than the hours you would spend on it. Aftermarket units for these engines are cheap - which is the trade: most run, but expect to set the mixture screws yourself, and expect more variation between units than a genuine part.

The one place the model badge genuinely matters is which carburettor to buy: the SRM-225 and the older SRM-210 take different Zama units despite sharing the same 21.2 cc class.

A new carburettor is not a fit-and-forget part on a two-stroke. It will need the idle and mixture screws set, and it needs clean fuel through it or it will gum up exactly like the last one. If the machine sits over winter, either drain the fuel system or run it dry.

The cheapest insurance is fresh mix at the right ratio - Echo sells its Power Blend at 50:1, part 6450050 for the gallon bottle. See tune-up parts and oil.

Which oil to run and how to mix 50:1 is a page of its own - Echo 2-stroke oil and the 50:1 mix.

That same 50:1 mix runs Echo's chainsaws too, but a saw also needs a separate bar and chain oil - the two are never interchangeable, as the chains and bars guide explains.

The same carburettor groups apply to the PAS power heads that share these engines, so if you are diagnosing a Pro Attachment Series unit start from the Echo PAS attachment parts overview.

The genuine Echo bar and chain oil numbers - separate from the 50:1 mix above - are on the bar and chain oil page.

Echo's entry chainsaws, the CS-310 and CS-352, and its backpack blower, the PB-580T, each run their own carburetor numbers outside the groups above - see the CS-310 and CS-352 parts and PB-580T blower parts pages.

The larger chainsaws split the same way: the CS-490 runs a Walbro WT-1009 and the CS-590 Timber Wolf a Walbro HDA-268, neither of which interchanges with the trimmer-range carburettor kits above.

The larger Echo SRM-266 trimmer steps up to a Zama RB-K112 carburettor, separate from the 210 and 225 groups, while the top-handle Echo CS-2511T chainsaw takes a Walbro WT-1208 (A021004690) - two more reminders to match the carburettor to the Walbro or Zama number, not the model badge.

Echo's two bigger backpack blowers each take their own carburettor too: a Walbro WYK-345/WYK-406 on the PB-770T, and a Walbro WYAB-1 on the flagship PB-9010T/PB-8010T pair - neither crosses to the PB-580T group above.

None of this matters if the engine never gets a spark to begin with - see Echo ignition coil for the no-spark test and the coil number by engine before assuming a carburettor fault.

Two more groups sit well outside the trimmer and blower range above. The commercial loop-handle Echo SRM-410U brushcutter takes a Walbro WYK-226, not any of the Zama units covered on this page. And Echo's larger, self-contained hedge trimmers - the HC-2020 and its family - run their own Zama RB-K118/RB-K119, separate from both the trimmer groups and the PAS hedge trimmer attachment.