4 cycling?

Discussion in '2-Stroke Engines' started by azbill, Apr 23, 2007.

  1. azbill

    azbill Active Member

    I have a strange noise coming from my engine, it sounds kinda like backfiring and results in major loss of power.
    Is this what i have heard called 4cycling?
    If so, what causes this and how do I prevent/fix it?

    ps even with my probs, I still made to the top of Mt Lemmon for the Spooky Tooth rally :lol: :lol: ( pics to follow )

  2. Thejman

    Thejman Guest

    just had this, it is the shitty kill switch that is doing it( beacuse it thinks for some reason it's pushed down a little bit. I took mine off to kill my engine i just push the carb lever up and pull the throttle with the clutch not on obviously ;p. It sounded like a little hand gun going off when it backfired lol.
  3. JosephGarcia

    JosephGarcia Guest

    Mine seems to be backfiring too, it gives a mildly loud (not too much louder than the normal engine sound) once every stroke, in time with the engine, no loss of power for me. probably resulted some this piece that fell out of my muffler.

    I heard running way too rich can affect the cycling of the engine. Will need to find where I heard this again.

    What gas/oil mix do you use?
  4. gone_fishin

    gone_fishin Guest

    to be clear on terms...if you're hearing "backfiring" does that mean you hear actual detonation? if so, i'd be looking for the first signs of a loose headbolt (the gasket seems to survive an actual leak) or a jug gasket leak.
  5. Guest

    Guest Guest

    Actual "four cycling" happens when the mixture is too rich. The engine fires once every other revolution- like a four stroke engine.
    This sounds very even, whereas a lean condition will make sporatic "popping" sounds and the occasional backfire.

    Both will cause a power loss, the former from too much fuel and too little combustion, the latter is much more harmful and can burn up an engine.

    If it just started outta nowhere and it's "four cycling" then check/change your plug. If it's a lean condition, check ALL the gaskets. Do the easy ones first, though I haven't heard of one blowing the center case gasket.
    Anthony 4k likes this.
  6. azbill

    azbill Active Member

    it is definitely not kill switch, I was running a throttle with switch built in...not anymore, tore it off in a fit of frustration (back to dax throttle)
    I just changed intake gasket to hightemp material +permatex on both sides, will try again tomorrow
    am also going to try carb with no filter, want to see if it got to gunky from when bad float was making it spew
    the funny thing is, it just kept pulling, going uphill, but on flat or downhill it makes a different noise and loses guts...like it wants the strain to work right :? :?

    also checked headbolts before... all nice n snug
  7. I just had a problem with backfiring ON MY WAY TO WORK TODAY. I took the carb apart and it kept happening. I have never changed the pin settings, but I think it may be too rich of a mixture or something.

    But I completely lose power and it seems like no fuel is getting to the engine after a few pops - any ideas?
  8. Okay I just went out and it looks like my kill switch fell apart at some point on my ride to work I'm kicking myself for not checking it first, because I smell like g'*** from taking the carb apart to check the needle/seat.

    well actually I smell like meatball sub now, but that's besides the point. ;)


    yeah it was the kill switch - now I need a new one.
    Last edited by a moderator: Aug 9, 2007
  9. Anthony 4k

    Anthony 4k New Member

    Best description I've heard yet, so mess around with jet size?
  10. Steve Best

    Steve Best Well-Known Member

    Yes. These come with a 70 so try a 68 or 65. Be careful, too lean is death.
  11. gary55

    gary55 Well-Known Member

    While you got the carb off you might wana pop the bowl off and clean up the float needle and housing. Just guessing, but it does sound like a 4 stroking issue. If it was running good and this all just suddenly started happening It is doubtful to be a jet issue unless the jet has loosened. If the float needle isn't seating you could be getting to much raw fuel into the venturi causing the 4 stroking. I also noticed you said Mt. Lemmon. The stock jet should be pretty close for Tucson elevation with a NT needing only tuning by needle adjustment. The chart says a # 68 is called for at your elev. and average temp., But I use a # 68 here in Prescott with the clip 1 notch down from the top with NT carbs on moderately modified engines.