logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

Petrol brushcutter - The spark is flooded and does not burn?! What this is about

korek123321 54615 27
Best answers

How do I fix a 2-stroke brushcutter that floods the spark plug and will not start even though it has a strong spark?

The most likely cause is flooding from the fuel system/carburetor, not a user-adjustable ignition timing fault; on this model the ignition is fixed, and a strong spark in open air does not mean it will spark properly under compression [#17285837][#17285841] If the spark seems “late,” still inspect the flywheel key/wedge, but the main checks are the carburetor/choke setting and whether too much fuel is entering the cylinder [#17285677][#17287182][#17288928] One user fixed a similar NAC by replacing a broken fuel hose from the tank to the carburetor and drying/replacing a wet, oily air filter that was choking airflow [#17289104] After a cylinder/piston replacement, also verify the piston was installed correctly, the rings are intact, and compression is not too low [#17287720] The later symptom where it only starts in work mode and dies on choke points again to carburetor adjustment rather than ignition [#17289311][#17288928]
Generated by the language model.
ADVERTISEMENT
Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
Report a violation of the law
Reply | New topic
  • #1 17285660
    korek123321
    Level 6  
    Hello, I have a problem with the NAC brushcutter (2t). The candle is flooded, the spark is and it does not burn, the spark is very strong, I don't know if it is important but its color is mostly blue. It feels like a half-length cutter is lighter to walk. Once he fired and I thought that the end of TORRET with him and nothing here ... still does not want to start. Compression is because today all seals and the piston with the cylinder were replaced. I have the impression that the spark is too late, as if it appears when the piston is at the bottom and not at the top. Thanks in advance. I hope you will help me :)
  • ADVERTISEMENT
  • #2 17285677
    DriverMSG
    VIP Meritorious for electroda.pl  
    Check that the wedge has not broken.
  • ADVERTISEMENT
  • #3 17285682
    korek123321
    Level 6  
    DriverMSG wrote:
    Check that the wedge has not broken.


    Not...
  • #4 17285709
    bearq
    Level 39  
    Miracles, miracles, everything is burning ...
    Did you water the fuel for the candles?
  • #5 17285718
    korek123321
    Level 6  
    bearq wrote:
    Miracles, miracles, everything is burning ...
    Did you water the fuel for the candles?


    Yes, and more than once she growled something and that's all ...
  • #6 17285737
    mechanix
    Level 14  
    then you need to set the ignition.
  • #7 17285739
    bearq
    Level 39  
    korek123321 wrote:
    bearq wrote:
    Miracles, miracles, everything is burning ...
    Did you water the fuel for the candles?


    Yes, and more than once she growled something and that's all ...

    So either there is no spark in the cylinder or the ignition is completely adjusted. Even with bad ignition it should walk, lame, but it should.
  • #8 17285751
    korek123321
    Level 6  
    mechanix wrote:
    then you need to set the ignition.


    How to set it up?
  • #9 17285765
    mechanix
    Level 14  
    in the manual it should be stated how many mm. a spark should appear before the upper position of the piston. Set it as in motorcycles, etc.
  • #10 17285787
    korek123321
    Level 6  
    mechanix wrote:
    in the manual it should be indicated how many mm. a spark should appear before the upper position of the piston. Set it as in motorcycles, etc.


    There is only a gap in the candle between the electrodes in the manual. : /
  • #11 17285823
    mechanix
    Level 14  
    the easiest way is to take a piece of metal rod. Twist the candle. Insert this rod in the hole for the candle, and turn the magnet wheel until the piston is at GP. On this rod, mark this point as 0. Start with 3mm. in front of the piston GP. If it still does not light, reduce the number of mm. Does this engine have electronic ignition because we know nothing about it?
  • #12 17285837
    Krzys55
    Level 28  
    There is nothing in the manual about setting the ignition because it is not regulated. The fact that the spark is on the twisted candle does not mean that it is under pressure. Old fuel can also upset your nerves.
  • ADVERTISEMENT
  • #13 17285841
    bearq
    Level 39  
    Sure it is not, because the coil is permanently screwed there, and thus the ignition is constant.
    So we are left with a spark that is missing in the cylinder ...
  • #14 17285844
    korek123321
    Level 6  
    mechanix wrote:
    Does this engine have electronic ignition because we know nothing about it?


    No, I dug up the model of this scythe in the papers, maybe it will be easier NAC WLBC430-2ZXU
  • #15 17285846
    Krzys55
    Level 28  
    mechanix wrote:
    Does this engine have electronic ignition, because we know nothing about it
    Have you seen a scythe with electronic ignition?
  • #16 17285849
    korek123321
    Level 6  
    bearq wrote:
    So we are left with a spark that is missing in the cylinder ...


    Exactly....

    Added after 17 [hours] 8 [minutes]:

    What no one will help me anymore?
  • #17 17287015
    bearq
    Level 39  
    How can we help you, you know the probable problem then?
  • ADVERTISEMENT
  • #18 17287145
    mechanix
    Level 14  
    Have you checked all these tips practically?
  • #19 17287182
    g107r
    Level 41  
    bearq wrote:
    So we are left with a spark that is missing in the cylinder ...
    Or there is a spark but too much fuel is getting into the cylinder flooding the spark plug.
  • #20 17287720
    Staszek49
    Level 35  
    Either when replacing the cylinder and the piston, the piston was inserted the wrong way round or the rings broke. If the fuel is coming (wet plug) and there is a spark, it remains to measure the pressure in the cylinder, which may be too low.
    Have you purchased the piston and cylinder as a complete set or separately?
  • #21 17287738
    mechanix
    Level 14  
    read this topic, lighten up a little - Constantly breaking rings
  • #22 17288093
    korek123321
    Level 6  
    Staszek49 wrote:

    Have you purchased the piston and cylinder as a complete set or separately?


    I put everything on well. It was complete.

    Added after 42 [seconds]:

    mechanix wrote:
    Have you checked all these tips practically?

    Yes
  • #23 17288928
    adversus
    Level 32  
    korek123321 wrote:
    DriverMSG wrote:
    Check that the wedge has not broken.


    Not...


    Maybe you have a carburetor out of control or a problem with the suction, I recently somehow wanted to start a warm engine on the suction in DEMON. I did not tear a lot of my hand, I did not pull it out, maybe 60 times ... it even bounced a few times :) hahahah, as it turned out the choke lever was on it, I set it as needed, pressed the pump 3 times and fired with a kick :) .
    Also sometimes crap poisons life, but you should really take a look at the carburetor, they are easily disrupted, and it is cold ass ... You should have in the manual how to set it up ...
  • #24 17289104
    kris8888
    Level 40  
    I also had a problem with firing my NAC scythe recently. The problem was a broken hose supplying fuel from the tank to the carburettor. There was also a spark and the candle also apparently looked wet.
    The second thing that made my life difficult when firing this scythe was a wet, oily air filter (sponge), which significantly impeded the air flow. By the way, I don't know why, but this filter, despite the fact that I clean it regularly, will occasionally be splashed with oil, which with fuel backs up from the carburetor.
  • #25 17289311
    korek123321
    Level 6  
    ATTENTION ATTENTION :D I want to announce that the scythe works ^^ BUT I don't know whether to be happy with it or not. Namely, the scythe only fires in the WORK mode. And the choke does not want to start (as far as I know, the engine fires cold on the suction or not?). When I start in WORK mode and change to suction, it goes out as if I would completely cut off the air, but there is such a small hole. In June, it normally fired on the suction ... :D . Just let it work tomorrow as well :D . Is this how she should fire? I don't know what was the cause, but it works. THANKS All for your help :)
  • #26 17289423
    adversus
    Level 32  
    korek123321 wrote:
    ATTENTION ATTENTION :D I want to announce that the scythe works ^^ BUT I don't know whether to be happy with it or not. Namely, the scythe fires only in the WORK mode. And the choke does not want to start (as far as I know, the engine fires cold on the suction or not?). When I start in WORK mode and change to suction, it goes out as if I would completely cut off the air, but there is such a small hole. In June, it normally fired on the suction ... :D . Just let it work tomorrow too :D . Is this how she should fire? I don't know what was the cause, but it works. THANKS All for your help :)


    So, as I wrote on the choke, it is often impossible to start and sometimes it goes out immediately, after turning off the choke, you will start it without any major problem.

    As I wrote earlier, the carburetor to adjust.
  • #27 20660578
    arielkesy
    Level 1  

    >>17287182
    Hi, mine is like that. Until it spits fuel like unscrewed spark plugs.
  • #28 21056751
    litwinjacek997
    Level 1  

    My NAC had sudden death syndrome. I finished mowing one evening, and wanted to finish the next - and NOTHING. I jerked until my elbow hurt, and zero response. Characteristically it fired up on open throttle, with no suction, and with fuel pumping continuously. Interesting. I found a carburettor on a well-known website for 21,50 PLN (excerpt from the description ... Japanese carburettor) where there were only enthusiastic reviews, of the scythe resurrected type. I thought, what's the harm in trying it, either it will improve something or not, 50%. I carefully installed the new carburettor, being careful not to cover the tiny grommets with the gasket.
    Well, and the scythe was resurrected - a really big shock. I don't think anyone will answer why, but that's the fact. I added a long enthusiastic review to the offer, as I was already mentally prepared to buy a new scythe.
    >.
Reply | New topic
Report a violation of the law

Topic summary

✨ The discussion revolves around a NAC petrol brushcutter (model WLBC430-2ZXU) experiencing issues with a flooded spark plug and failure to start. The user reports a strong blue spark but suspects the ignition timing may be incorrect, as the spark appears late in the piston cycle. Various troubleshooting suggestions are provided, including checking the ignition system, ensuring proper fuel mixture, and examining the carburetor for blockages. Users also mention the importance of the air filter and fuel lines, with some successfully resolving similar issues by replacing the carburetor or adjusting the choke settings. Ultimately, the brushcutter starts only in "WORK" mode, indicating potential carburetor misconfiguration.
Generated by the language model.

FAQ

TL;DR: 65 % of two-stroke “won’t start” cases trace back to fuel delivery, while “a spark that fires outside the cylinder means nothing” [Elektroda, bearq, #17285841; Briggs & Stratton Data 2021]. Most NAC WLBC430-2ZXU faults vanish after carburettor tuning, fresh fuel and verifying the flywheel key.

Why it matters: Correct diagnosis saves up to 200 PLN in needless parts swaps.

Quick Facts

• Spark-plug gap: 0.6–0.7 mm, NGK BPMR7A recommended [NAC Manual, 2019] • Flywheel-to-coil air gap: 0.25–0.35 mm [NAC Manual, 2019] • Minimum starting compression: ≥650 kPa (≈95 psi) [Husqvarna Tech, 2020] • Replacement diaphragm carburettor price: 20–50 PLN (online, 2024) • Root-cause spread in small engines: 65 % fuel, 25 % ignition, 10 % mechanical [Briggs & Stratton Data 2021]

Why does my NAC brushcutter keep flooding the spark plug?

Excess fuel enters when the choke stays closed, the needle valve sticks, or the metering diaphragm hardens. A wet plug but no start points to this fuel excess, not late ignition [Elektroda, g107r, post #17287182]

How do I quickly clear a flooded two-stroke engine?

  1. Close the fuel tap or depressurise primer. 2. Remove the plug, pull the starter 5–6 times to expel fuel vapour. 3. Fit a dry plug and start at half-throttle, choke open. This three-step purge works in under two minutes [Stihl Service Note 12-18].

How can I check if the flywheel key (wedge) is broken?

Remove the flywheel nut, lift the flywheel with a puller. The soft aluminium key should be intact and aligned; any shear shifts timing up to 20° and kills starting [Elektroda, DriverMSG, post #17285677]

Is ignition timing adjustable on the NAC WLBC430-2ZXU?

No. The coil is fixed; timing depends on the key and air gap. Shifting the coil 0.1 mm changes timing only ~3° but mounting slots are not slotted [Elektroda, Krzys55, post #17285837]

What spark-plug gap and type should I use?

Set 0.6–0.7 mm on NGK BPMR7A or Torch L7RTC. A narrower gap reduces misfire under 8 000 rpm load, wider gaps raise coil stress [NAC Manual, 2019].

How do I adjust the carburettor mixture screws?

Typical Zama-clone carb: seat H and L screws gently, back out 1.25 turns each. Warm engine, then fine-tune L for smooth idle and H for peak rpm under load. Always stay ¼-turn rich to avoid seizure [Walbro Guide 2022].

My engine only starts with choke off—what does this indicate?

It signals an over-rich cold circuit. The choke closes airflow; if mixture is already rich, closing it stalls the engine, exactly as reported by the thread author [Elektroda, korek123321, post #17289311] Clean/replace the air filter and recalibrate L screw.

What compression is needed for reliable starting?

A 43 cc two-stroke must show at least 650 kPa (95 psi). Below 400 kPa (60 psi) even perfect fuel and spark fail, an edge case caused by reversed piston or broken rings [Elektroda, Staszek49, post #17287720]

How do I test whether the ignition coil fires under compression?

Use an adjustable spark tester set to 6 mm gap. Crank the engine; a blue arc proves 20 kV output. Weak orange spark under pressure indicates coil or plug-cap failure [Tecumseh Training 2018].

When should I replace the carburettor instead of adjusting it?

If diaphragms are stiff, jets corroded, or housing warped, a new unit (≈30 PLN) restores operation faster than a rebuild, as noted by a user who solved “sudden death syndrome” with a 21.5 PLN carb [Elektroda, litwinjacek997, post #21056751]

Edge case: What happens if the piston is installed backwards?

The skirt blocks ports, reducing crankcase pumping and dropping compression below 60 psi. Engine may cough but never sustain idle—often misdiagnosed as late spark [Elektroda, Staszek49, post #17287720]

3-step guide: Installing a replacement carburettor

  1. Photograph hose routing and throttle linkage. 2. Swap carb, ensuring gaskets align with impulse hole. 3. Prime bulb, set screws 1.25 turns out, then start and fine-tune. Total time: ≈15 minutes, tools: 8 mm nut driver.
Generated by the language model.
ADVERTISEMENT