5 things to know — won't-stay-running on the MM4 4-stroke

1. The BHX2500CA is 4-stroke MM4 — straight gasoline, NOT a 50:1 mix. Common enough mistake that it surfaces in the r/smallenginerepair thread when the OP has to clarify mid-comments. If anyone's been adding 2-stroke oil to the fuel, that's a clue toward different problems.
2. Stale fuel without stabilizer is the #1 cause of bog/stall after storage. Gas left to sit varnishes and gums the carb jets. "You probably had gas sit without stabilizer. Clean the carb out and soak in carb cleaner. Get the good chlorinated kind." — u/_Tigglebitties
3. Carb clean is the standard first move. Three of three threads converge on this: remove carb, soak in chlorinated carb cleaner, blow through jets, reassemble. If cleaning doesn't suffice, a rebuild kit is cheap (~$10-20).
4. Two adjustable screws on the carb drift after storage. Idle screw + throttle screw. "There's an idle Screw, and a normal throttle screw. Both can be adjusted." — u/zedsmith. Worth checking even when the carb's clean.
5. Primer bulb is consumable. If it's soft / cracked / not building pressure when squeezed, replace it. Thread 3's OP started by replacing the primer bulb (then still had bog at throttle → root cause was carb).

Full distillation — what the community converges on

Most likely cause (across all 3 threads): stale fuel from off-season storage has gummed the carburettor. The blower starts and idles, but bogs / cuts when throttle is applied because the jets can't deliver enough fuel under load.

Standard troubleshooting sequence:

1. Drain old gas, fill with fresh gas + stabilizer
2. Replace primer bulb if degraded
3. Pull, clean, soak the carb (chlorinated carb cleaner — "the good kind")
4. Check + adjust idle screw and throttle screw to spec
5. Replace air filter and spark plug as cheap preventative measures
6. If still bogging: rebuild kit or new carb (cheap, ~$30 OEM)

Deeper diagnosis (only if the standard sequence doesn't fix it): pull the recoil cover, inspect for carbon buildup on valves and lifters. Thread 2's OP went all the way to this level and shows the rebuild is feasible DIY for the determined.

Brand-quality context: pre-Makita Dolmar units (before the acquisition) had a reputation for "add gas, change oil, run for 15 years" robustness. Post-acquisition Makita-produced BHX units have variable quality — worth knowing for repair vs replace decisions if a unit keeps having issues even after a thorough service.

Why this matters

Both Makita BHX2500CA units in the pair are flagged for service after winter storage. The community signal points overwhelmingly to stale-fuel carb gumming as the likely cause — exactly the failure mode "gas left sitting from last season without stabilizer" produces. When N&J General Repair gets the pair, the conversation to have:

"I've got two Makita BHX2500CA blowers, both bogging at full throttle after winter storage. Please plan for: drain stale fuel + replace with fresh + stabilizer · primer bulb inspect/replace · carb clean (chlorinated solvent) ± rebuild kit if needed · idle + throttle screw adjustment · air filter + spark plug replacement. Budget for each unit independently; the carb work is the heaviest line item."

This gives N&J a structured pre-diagnosis so they're not starting from "won't run, find out why" — saves them time, saves us money on labour, and surfaces the brand-quality context (pre/post Dolmar acquisition) for repair-vs-replace decisions if either unit fights us.