Engine Trouble Engine loss of power when hot n fourstroking alot

Discussion in '2-Stroke Engines' started by four cu, Aug 19, 2014.

  1. four cu

    four cu New Member

    On third take of fuel n still same problem it's getting hot quick and fourstroking. I've tried main needle nothings leaking. Floats where it's soposed to be. New plug good ngk kind. Tried three different gas to oil ratios. Please help. I'm more concerned why it gets hot n looses power so fast.
     

  2. crassius

    crassius Well-Known Member

    if you can find a point in the throttle at which it 2-strokes when going uphill, then it sounds like you're OK and just need to wait till the rings finish seating
     
  3. four cu

    four cu New Member

    It's four stroking at random mostly in higher revs. Gets hot real quick
     
  4. crassius

    crassius Well-Known Member

    I'd keep it away from high revs till it runs in more
     
  5. HeadSmess

    HeadSmess Well-Known Member

    now, is it really four stroking? what happens when you open the throttle completely? and what exactly do you define as "hot"?

    "hot" is when smoke starts coming off any oil on the cylinder. you cant hold a finger on the head for less than two seconds (though i do have really thick skin so maybe not :jester:) and thats caused by really lean jetting. which would not be "fourstroking" at all. really advanced ignition could do it too..


    might have gotten one of those lemon engines i had the misfortune of once purchasing, the only engine ive seized yet :)


    whats the plug number, and whats its insulator look like after a good run?
     
  6. four cu

    four cu New Member

    I tried different jets n no better appeared to be bigger n smaller then I currently use. After a good run less then five km just crusing at half to 3/4 it becomes hot n has NO power. It only sounds like fourstroking once it's got warm. Im using b6hs ngk 20140822_130750.jpg
     
  7. four cu

    four cu New Member

    Seems to be getting hot way to quick I've built up seven bikes n this is first issue that has been such a headache and not a nice fix. Once again I'll Check fir leaks but ice checked plenty of times.
     
  8. crassius

    crassius Well-Known Member

    I'm at that point at which I'd have to see & hear it to know much more, but that plug looks a bit like it was leaking thru the threads - I'd clean the area around it & see if oil appears.
     
  9. four cu

    four cu New Member

    Would Teflon tape work
     
  10. four cu

    four cu New Member

    Screenshot_2014-08-22-17-10-00.jpg

    Seems to be boiling fuel that was after ten min rip to get new plugs
     
  11. HeadSmess

    HeadSmess Well-Known Member

    yeah, teflon tape works but as long as youre tightening the plug up properly, its pointless. (and run the risk of insulating it from the head which will prevent spark) heat is right, colour looks good, if a touch rich really.

    remember to use the killswitch at the throttle position youre testing when checking the plug colour. pointless if you let it idle at all.


    the way it idles is the best sign of air leaks...if it just revs out, even with the idle screw backed right out...theres an air leak.


    does it start easily or need some persuasion?

    im starting to really suspect its an ignition issue. happen to have spare CDI unit to pop on? check position of keyway in magnet, might be a bad one. its not too easy checking for ignition timing without a timing light, and the expense of even a cheap one just isnt really worth it if its a one off thing. jaguar did post a schematic for a simple timing light with an LED, might be worth searching for. then you gotta find TDC, and mark the magneto for it, but that isnt too hard to do, either. google :)

    where is your cdi located? possibly getting too hot?

    and exhaust. pop the exhaust off. can you blow through it easy peasy or is it feeling all restricted? there should be some resistance, but not TOO much.


    this one IS a doozy! ;)

    last thoughts.... the piston is oversized, cylinder is undersized... once it gets warm, they start rubbing and wham... did happen to my last skyhawk, but took a good 5-6000km to start doing it! only way to check that is to pop the head, check the bore with piston at the bottom. any scratches? remove cylinder, trying to keep bottom gasket intact. check piston for same thing, big patches where its obviously been rubbing. there wil always be some rubbing, but if its a whole section, aye...that will do it. might simply be the relief at the top of the piston, around the rings, wasnt machined in deep enough. they do expand when hot!


    oh! and the chrome plating! if thats got any patches missing, same deal... it will start fine, run fine, but after a few minutes, it will die or lose power...
     
  12. crassius

    crassius Well-Known Member

    the ring at the top of threads is a gasket, if threads are not damaged, that is all you need - I'd avoid tape

    bubbles could easily be from too much vibration in the carb (which can also cause a power loss)
     
  13. four cu

    four cu New Member

    The bubbles start after its shut off
     
  14. four cu

    four cu New Member

    20140823_083244.jpg
    Does it matter which way the arrow points on the piston. And that's pic after plug chop. Once again it was cool morning n got hot real quick it seems to have no leaks whatsoever
     
  15. four cu

    four cu New Member

  16. crassius

    crassius Well-Known Member

    plug looks a bit whiter than I usually run them
     
  17. four cu

    four cu New Member

    Should I go down on slide needle or replacement adjust my float. Note I have changed to bugger and small jets with no effect
     
  18. crassius

    crassius Well-Known Member

    I always start with adjusting the needle as that's the quickest to undo if wrong.
     
  19. jaguar

    jaguar Well-Known Member

    four stroking is from too rich jetting so you should have had some success with smaller main jet. maybe you didn't go low enough.
    arrow points toward exhaust.
    bubbles in gas line are totally meaningless. the fuel is not "boiling".
    get a cheap compression tester to know what your compression is. guessing just don't cut the mustard.
    engine heat can change how well or how bad loose screws at the stator coil allow conduction for the ground loop of the ignition circuit. sandpaper where those screw heads contact the stator coils frame.
    "gets hot quick" don't mean anything. 2 strokes do that. Get a temperature gauge for the head. JNMotors sells one.
     
  20. four cu

    four cu New Member

    Ok so I sanded it can't try right now ****ing down rain. The arrow on piston points at carb. Is that a issue?
     
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