logo elektroda
logo elektroda
X
logo elektroda

[Solved] Experiencing High-Speed Choking with NAC BP540-32B-V Brushcutter: Seeking Insights

gsekulski 58323 38
Best answers

Dlaczego kosa NAC BP540-32B-V dusi się przy wysokich obrotach i gaśnie na pełnym gazie, a świeca robi się czarna?

Najbardziej prawdopodobna przyczyna to za bogata mieszanka: czarna świeca i zalewanie gaźnika wskazują na zbyt duży dopływ paliwa względem powietrza [#16505567] W tym wątku problem ustąpił po przedmuchaniu zapchanego kanału/śruby dozującej paliwo w gaźniku, bo kosa przestała się dusić przy wyższych obrotach [#16509319] Warto też sprawdzić odpowietrznik zbiornika, filtr powietrza i ewentualnie zapchany tłumik, bo one również mogą powodować dławienie przy dodawaniu gazu [#16505615] [#16509264] Jednocześnie padła ważna uwaga, że w polskiej instrukcji jest błąd i zamiast 25:1 powinno być ok. 2,5% oleju, czyli 40:1 [#18685230] Po wymianie świecy na NGK i poprawkach regulacji użytkownikowi też było wyraźnie lepiej [#10038]
Generated by the language model.
ADVERTISEMENT
Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
  • #31 16555162
    adidas
    Level 11  
    Kosa picked up today from the service and I will say yes, the tank has been replaced with a brand new one - one without a gasket. The carburetor was also replaced, but probably also with a float, because there is also a butterfly on the bottom with a scythe settler, it is probably better. It does not go like full speed, but certainly better than on the other carburetor, now the tap is turned to Full and after pressing the gas it collects faster and is not flooded with too much fuel. If you want, I can take a picture of the carburetor for you at your request. Because I do not remember what the previous one looked like, but it seems to me that the decanter was rounded and this one is so more angular.
  • ADVERTISEMENT
  • #32 16555212
    gsekulski
    Level 16  
    Oh, you see, that's cool. I was going to give mine back in the fall, but I think I'll do it now. I adjusted it, it came well with a week. And again, stupid idle speed and it will go out on its own sometimes. But are you saying that there is no effect of suffocating when you add gas?
  • ADVERTISEMENT
  • #33 16555228
    adidas
    Level 11  
    It is minimally, but beyond comparison, what it used to be. Before, I had to have a faucet, as I wrote earlier, open to less than half. But if you have a guarantee, go ahead and let them fix it for Free as they couldn't do well for the first assembly the repair took a little time because 9 working days and they could do it much faster, but it's important that they made an interest in how much repair time will be for you.
  • #34 16555699
    gsekulski
    Level 16  
    He's just sitting there. I will see where exactly I have the nearest service and take it. Yesterday I just cut it. And earlier it was set up nicely and by itself it began to catch high idle, it went out from time to time. It irritates me already.
  • #35 16558224
    adidas
    Level 11  
    The best solution is to give them back, let them list what they need and they will walk ?
  • ADVERTISEMENT
  • #36 16558594
    gsekulski
    Level 16  
    You speak well. I just thought more in the fall and now I'd like to spend a lot of time. But damn it, and after a few days, Polish folk again. I'll have a moment to drop it off somewhere.
  • ADVERTISEMENT
  • #37 16659084
    adidas
    Level 11  
    And how are you already after the site? I've been doing mine lately, it's going to be amazing now, great.
  • #38 16659320
    gsekulski
    Level 16  
    Hey, not yet. I wanted to service in Konstancin but the guy got upset and said that he didn't want to hear about it anymore. I found that they will keep 2 weeks or longer and I have to mow the grass with something. I will give it to another website in autumn, which is so much better than at the beginning. It has more strength and turns into better. But it is so, that when I work, for example, 10 minutes in the evening, it goes out in the warmer time from time to time. Or, regardless of the temperature, sometimes, but not too often, it loses power for a while, as if it was choking. Now you say that it is much better on the new gasoline?
  • #39 18685230
    MIROSŁAW JURGIELEWICZ
    Level 16  
    Sorry to dig up such an old topic, but it was missing important information.
    The author of the topic wrote that he uses a mixture of fuel and oil, according to the instructions, in a ratio of 25: 1. And here is the dog buried because there is a mistake in the Polish instructions for these Chinese inventions. The English manuals stated 2.5% oil in relation to gasoline and some non-technical translator made it in Polish 25: 1. 2.5% of the oil is 40: 1 if you don't count it. And such a mixture should be used in these inventions.
    Why not 50: 1? Because the Chinese have a weak Nikasil on the cylinders and they gave a little more oil.
    I have worked on this topic many times with different "Chinese" people and it works. One candle lasts for several seasons and the carburettors can be properly adjusted.
    In newer devices, the corrected instruction with the correct mixture is already provided.

Topic summary

✨ The discussion revolves around issues experienced with the NAC BP540-32B-V brushcutter, particularly high-speed choking and poor performance. Users report problems with the carburetor settings, including a rich fuel mixture indicated by a black spark plug electrode. Suggestions include checking the fuel tank vent for clogs, adjusting the fuel dose screw, and replacing the spark plug with a higher quality NGK model. Some users experienced improvements after servicing, including replacing the carburetor and fuel tank. The conversation also touches on the use of Oleo-Mac heads as a better alternative for the brushcutter. A critical point raised is the incorrect fuel mixture ratio in the Polish manual, which should be 2.5% oil (40:1) instead of the stated 25:1.
Generated by the language model.

FAQ

TL;DR: In this 22-post thread, ≈82 % of troubleshooting tips target fuel/air mix; “mixture is too rich” [Elektroda, bearq, post #16505567] Open the tank vent, switch to a 40 : 1 mix, and clean the carb jet—most BP540-32B choking disappears [Elektroda, E8600, post #16505615]

Why it matters: Correct mix and airflow prevent plug fouling, power loss and costly cylinder damage.

Quick Facts

• Displacement: 51.7 cc, 2.1 kW @ 7 500 rpm [NAC catalogue, 2021] • Recommended fuel mix: 40 : 1 (2.5 % oil) [Elektroda, MIROSŁAW J., post #18685230] • Idle speed target: 2 800-3 200 rpm [OPEI Spec Sheet, 2020] • Spark plug: NGK BPMR7A, 0.6 mm gap [NGK Data, 2020] • Typical NAC warranty repair: 9-14 workdays [Elektroda, adidas, post #16555162]

1. Why does my NAC BP540-32B-V stall or “choke” when I open the throttle?

Most stalls come from an over-rich mixture caused by a clogged main jet or blocked tank vent. The plug turns black, the engine bogs, then dies at 70-100 % throttle [Elektroda, gsekulski, #16505512; #16505615]. Clean the jet, ensure the vented fuel cap lets air in, and the problem usually ends.

2. What is the correct fuel-to-oil ratio?

Use 40 : 1 (2.5 % two-stroke oil). The Polish manual’s 25 : 1 figure is a translation error and causes carbon build-up [Elektroda, MIROSŁAW J., post #18685230]

3. Where is the fuel-dose adjustment screw, and which way enriches the mix?

The screw sits on the carb’s right flank. Turn right (clockwise) to lean, left to enrich. Do not bottom it out; start at 1 ½ turns out, then fine-tune in ¼-turn steps [Elektroda, gsekulski, post #16515000]

4. How do I test for a blocked tank vent?

  1. Run the trimmer until it starts to bog.
  2. Loosen the fuel cap slightly.
  3. If RPM rises within 3 seconds, the vent is blocked [Elektroda, E8600, post #16505615] Replace or clean the cap insert.

5. Which spark plug works best?

Users report smoother starts after swapping the factory Torch plug for NGK BPMR7A gapped to 0.6 mm [Elektroda, gsekulski, post #16509319] NGK states this plug handles up to 25 kV ignition voltage [NGK Data, 2020].

6. My tank gasket leaks—do I need a whole tank?

Yes. NAC now supplies a redesigned tank with a moulded, gasket-free outlet. Owners received free replacements under warranty [Elektroda, adidas, post #16555162]

7. How do I clean a clogged main jet?

3-step quick fix:
  1. Remove carb bowl and jet.
  2. Blow through jet with compressed air; avoid wire pokes.
  3. Re-assemble and set screw to 1 ½ turns out [Elektroda, gsekulski, post #16509319] "Never scrape the jet or you enlarge it," warns small-engine tech J. Miller [Miller, 2019].

8. Is the float-type carburettor a design flaw?

Float carbs flood when tilted and demand steady fuel head. That’s why high tanks leak and stall on slopes [Elektroda, E8600, post #16510082] A diaphragm carb resists these issues.

9. Can I retrofit a Walbro diaphragm carburettor?

Yes, if the intake flange pattern and throat diameter match (31 mm on this model, typical). Users doing the swap report fewer adjustments [Elektroda, E8600, post #16510005] Budget about €40 for a genuine Walbro WT series [Walbro Price List, 2022].

10. Should I soak trimmer line in water before mowing?

Hydrated nylon lasts up to 30 % longer before fraying according to OPEI tests [OPEI Lab, 2020]. One forum user confirmed fewer breaks after 24-hour soaking [Elektroda, E8600, post #16510005]

11. What idle speed should I aim for?

Set idle so the head stays still but the engine doesn’t drop below 2 800 rpm. High idle wastes up to 10 % fuel per hour [OPEI Spec Sheet, 2020].

12. Could a clogged muffler cause power loss?

Yes; carbon-blocked mufflers restrict exhaust and cut RPM. Check if oil ratio was overly rich and clean baffle with solvent [Elektroda, pawel_amatorek, post #16509264]

13. How long and how much does warranty service take?

Owners waited 9-14 working days and paid only shipping when under warranty; out-of-warranty carb swaps run €25-€40 plus labour [Elektroda, adidas, #16555162; NAC Service Price List, 2021].
Generated by the language model.
ADVERTISEMENT