Engine Trouble 66cc 2-stroke engine bogging? help me!

Discussion in '2-Stroke Engines' started by pineiroadrian, Dec 14, 2010.

  1. pineiroadrian

    pineiroadrian New Member

    ok guys im having an issue with my moped. its got a 66cc 2-stroke engine. right now its using 25/1 fuel ration i believe. the fuel in the tank has been sitting there for a while. i started the bike and let it warm up. then when its all nice and warn, the bike idles perfectly, i rev the engine slowly and its all good untill it get to high rpm. and if i punch the throttle it just boggs??
    i got on it and rode around, it was fine at low speeds, but when i give it throttle it seems like it looses power and just boggs. my carb has no lsn or hsn adjustments. could it be that the fuel filter is dirty, or that the gas ha been sitting for too long?

    thanks in advace for the help :)

  2. NBP MotorSports

    NBP MotorSports New Member

    Check this post, I just finished reading it, you might find it helpful.

    Phil_McCracken Phil_McCracken is offline
    MBc Member
    I sortta thought this has been done before, anyway I'll add a couple of things.
    1. The clutch operating arm, out of the box it is at the wrong angle for smooth and light operation, it tends to "pull" the inner cable.
    Ive added a couple of pics, its on splines, if you moved it towards the carby a couple of splines you get a straighter run for the inner cable and makes for 2 finger opperation and longer cable life.
    2. Ok the magneto, has been said you should seal the grommet for the wires and the cover to stop water entering, while the cover is off have a close look at the magneto winding and check for any stray strands of wire.
    I was chasing a misfire and one night i was running it out the back and noticed a spark jump from the crank case to the frame.
    I took off the wiring, coil and mag and found this almost invisible tiny strand hanging out of the winding, Ive added a pic with an arrow, is hard to see.
    Misfire gone and for sure it would have eventually caused magneto failure.
  3. motorpsycho

    motorpsycho Active Member

    did it always run this way or is this a recent problem? what is the weather like where you live? if it's really cold out, the cold air will make an engine run leaner than it would when it's warm outside.
    normally a bog at 3/4 to wide open throttle is because the air-fuel ratio is too lean.
    Last edited: Dec 14, 2010
  4. Pablo

    Pablo Motored Bikes Sponsor

    It could be old fuel as well.

    What does your plug look like?
  5. pineiroadrian

    pineiroadrian New Member

    recent problem. makes sense cause its the first time i started it since it got cold. im in FL but its in the 30-50F range. :(.
    im gonna drain all the old fuel anyways. clean the carb, and put fresh fuel in there. what ratio should i use now?
  6. pineiroadrian

    pineiroadrian New Member

    the fuel has been sitting.
    ill take the plug out and snap a pic.
  7. pineiroadrian

    pineiroadrian New Member

    pictures of my engine to help you help me :)

    guys i really need some help my bike starts and rides at low speeds perfectly, but when i get up to speed or give it more than half throttle it just bogs, the rpms seem to go down and it has like no power. its not my carb because, i completely tore it down and cleaned it today, the jet is clear. and i cleaned both valves aswell, checked my magneto and put a new fuel filter/ tubing. took my head off and this is what i saw. (in the pics).
    i think im too lean, i dont really remember what the mixture im using is but its like 25:1. should i go leaner like 40:1? and i moved the clip on the slide needle to the top (leaner). should i put in a new plug and put in 40:1 or what would you recomend? the weather here is like 60-70. please i need your help, theres a buy coming on sunday to buy the bike and if its not running properly he wont buy it :( thanks in advance.

    Attached Files:

    Last edited: Dec 30, 2010
  8. i_Bones_i

    i_Bones_i New Member

    That plug is drenched. Did you flood it out trying to start it right before you took it apart? How many oz. of oil are you adding to a gallon? That plug looks to me like it has ALOT of unburned oil on it. You're using 2-stroke oil right?? Things being wet make the carbon deposits look even darker in color. How many hours are on this engine? We run oily premix compared to your average 2 stroke because our direct drive bikes run extended periods of high RPM, so extra carbon build-up is bound to happen in this type of situation. But if we didn't run oily mixes our bikes would be likely to overheat on long hauls. It's hard to say what's really wrong from looking' at a few pic's of your piston and plug, wish I could hear it run. I'm no mechanic so everything I just said might be equal to :poop: I am only applying my own common sense. GL fellow mb'r and I hope u get the problem solved.
    Last edited by a moderator: Dec 15, 2015
  9. pineiroadrian

    pineiroadrian New Member

    Thanks bones :)
    And your wish will come true, I took a
    Video of it right before taking it apart. Here's the URL http://www.youtube.com/watch?v=ZqpORCDq3DU
    I think I'm using 18:1? Or around there. I think I'm too rich, because I'm still fueling from the big batch of gas I mixed when I was breaking it
    In. That fuel has been sitting for many months too. So I cleaned the piston, cleaned the plug, emptied out my fuel tank. Gonna go get fresh gas tomorrow and use 40:1? That's why I'm debating my bike has
    80 miles on it give or take a couple.
  10. i_Bones_i

    i_Bones_i New Member

    Well, she runs smooth on idle and seems fairly responsive. It could be old fuel I suppose. Something else to check though, you said it loses power on top end, perhaps the baffle in the muffler is getting clogged with gunk? With only 80 miles on it, its unlikley but it would explin both power loss on top end and extra carbon buildup in the cylinder. If it cant get rid of exhaust fast enough at high rpm it would restrict it's power and also it would leave exhaust in the cylinder and create a dirty burn. :confused:
  11. Stan4d

    Stan4d New Member

  12. pineiroadrian

    pineiroadrian New Member

    hmmm dint think of the exhaust! but ive tried to open it before and it seems to be welded shut ?
  13. pineiroadrian

    pineiroadrian New Member

    Maybe? But I watched a video on another thread and it demonstrated an engine four stroking, it
    Kinda sounds like it's hitting a re limiter almost? But now mi bike sounds like it's just bogging, and loosing rpms and power, I'm to rich I think, but now I'm also worried about the pipe?
  14. Stan4d

    Stan4d New Member

    read that thread.....it covers alot that you have mentioned. Then scroll to the bottom and you will find related links.
  15. i_Bones_i

    i_Bones_i New Member

    Just pull the muffler off and go for a ride. :devilish: If the problem is gone then you know where to look. Just don't try it at 2am. :shout: As for it being welded, you would see weld beads on the outside of the end cap. Mine clogged up after 100's of miles. I found myself holding the bike at WOT not even realizing it. Bike would max out about 20 mph. Mine had 2 screws in it and still even after removing them I had to fight with it to get it out. I ended up busting the little 1 inch tip off and screwing a course threaded bolt into the little hole, clamping it in a vise and beating the bolt with a hammer in an away from the muffler fashion.....I don't know how to explain it. After I got it out I just drilled a few holes through the baffle plate, it made the bike louder but I've not had the problem in over 2000 miles since. 4-stroking could be the problem. However!! A 4-stroking 2-stroke is caused from running too rich. (Too much fuel not enough air) In theory, my brain says that a clogged exhaust would limit an engines air intake and cause a richer running engine. And not only that, when my muffler gummed up my bike began 4 stroking at times. But your bike has only 80 miles on it.....that's like 4 hrs run time or so. The exhaust shouldn't really be dirty yet. Once again, I am not a mechanic. My theories are only theory's.......:-/
    Last edited by a moderator: Dec 15, 2015
  16. Stan4d

    Stan4d New Member

    I really wish you would take the time to read the threads people direct you to. Kind of an etiquette thing. It is along the same lines as searching before posting to prevent duplicate content.
  17. pineiroadrian

    pineiroadrian New Member

    thanks for all your help! man i tried 50:1 and the guy came like 20 minutes ago. the bike has never run as good as it did! he was happy we agreed on $400. sad to see it go but it was time.
  18. wackey101

    wackey101 Member


    check your jet in your carby could be loose and could be old fuel
  19. Tumbledove

    Tumbledove New Member

    Check your motor mounts! I was loosing top end power also. The bike, (HT 48cc), would build up good speed until the higher rpm's and die, then picking back up in the middle range. I noticed a daily decrease of a mile or two. I gradually went from 30+ to 22mph, even as I was investigating the following remedies;

    I tightened the intake system, cleaned the carb, changed jets, adjusted the c-clip, adjusted the prongs in the carb bowl, installed a new fuel filter, ran a little SeaFoam, vented the tank, installed a new plug, and flushed the exhaust. Nothing! Then I noticed that the motor had a slight shake to it while I was removing the plug again. The engine hardware was not tight anymore so I carefully snugged the motor mounts. The only other thing that I did was spray a little wd40 behind the magneto cover, cdi wire input, (very little), and inside the spark plug wire cap. I did this to drive out any possible moisture that may have entered and compromised a good connection. I then took it for a test ride. She hit a nice top speed again right away! I was just about to give up. (Not really). I am leaning toward loose motor mounts as the cause of the loss of WOT power and strange engine behaviour. Just my 2cents. I hope this helps someone out there having this type of trouble. Good luck.

    At least now I have a spare carb, magneto, cdi and plug cap on the way, which I ordered before I found the fix. :detective:
    Last edited: Jul 13, 2011
  20. Chase Logoz

    Chase Logoz New Member

    Cool. ive seen a lot of threads with trouble like that. Makes sense to me. No telling what kind of froth was building up in the carb bowl. That could shut a motor down by itself. Locktite should stop that from happening. or at least help out. If your getting over 30 from the small ht thats pretty good. what is on those handlebars anyhow?