misterious engine problems

Discussion in '2-Stroke Engines' started by keatonx, Nov 29, 2010.

  1. keatonx

    keatonx Member

    hi. I have a used 31cc 2 stroke i am making a small go-cart with. The seller said it had a leaky bladder. I have no clue what he meant by bladder. Right after I paid for it, I tried to get it running. After pulling the starter untill my hand had a bloody welt on it, it puffed out lots of white smoke and bogged constantly. It dripped oil out of the muffler, too. Then it flooded itself WHILE running. Once stopped, it leaked gas from the carb. Couldn't start it. I had it in peices many times, and noticed a rigid diaphragm. I fixed that by soaking it in penetrant, and gave it a carb clean. Today it ran perfectly, with almost no smoke, and reved like my KTM race bike. But it still leaked gas from the carb. And when I checked the spark plug, it was black and crusty. Any ideas? Been working on it for weeks now. Thanks!

    P.S. It has tons of compression! Will this help or hurt my torque?
    Last edited: Nov 30, 2010

  2. HeadSmess

    HeadSmess Well-Known Member

    simple fix....scour the rubbish heaps til you find something with a similar carby...chainsaw, edger, brushcutter whatever... replace it with the one you have now.

    the carbs should usually have two needles...hi and lo.

    turn both completely in, then wind out 2.5 turns. same with the idle screw.

    start it, letr it warm a minute, then give it full throttle. adjust the "hi" needle until you hear the RPM peak, then back out just a touch.

    do that as quickly as you can... engines dont like WOT for too long

    then let it idle. adjust the idle screw til its a fairly high idle, then adjust the "lo" screw til once again, it peaks. then readjust the idle screw to a nice idle.


    you might find replacement diaphgrams at a mower shop, but its easier to just swap carbs...
  3. keatonx

    keatonx Member

    I have another weed eater with a carb on it. It's kinda low-quality and it's slightly corroded, but it should work. Also, when it runs (with the old one), it sprays a small amount of gas out of the air inlet. I am using a more powerful weed eater with this thing in the crank case that i assume acts as a reed valve.(unlike most other models, the carb leads to the crank, not the cylinder.) could that be leaking, causing air to shoot through the carb?
  4. HeadSmess

    HeadSmess Well-Known Member

    reeds? then theyre leaking.

    if they are reeds.

    also be why its hard to start.

    check the compression...in BOTH directions. theres an UP and a DOWN compression on 2 strokes... more obvious on reed valves engines.
  5. keatonx

    keatonx Member

    I have noticed that whenever i soak old rubber parts in WD40 of penetrant, it gets softer. Could i use this to give my reed a better seal?
  6. HeadSmess

    HeadSmess Well-Known Member

    youll find reeds are either some type of fibreglassy cloth sorta thing, stainless steel, or plastic.... wont be affected by wd40.

    the actual sealing surface that the reeds seat on...maybe.


    the reeds usually bend, stopping them from sealing. turning them over works well :) unless they have what the last set i saw had... a crease.

    youre also better off using auto tran fluid for "softening" plastic etc.... 250 times better than amour-all which is an overpriced gimmick that does more harm than good.... try it on those old faded plastics!rubbers! tyres! excellent stuff :)
  7. keatonx

    keatonx Member

    I was gonna flip it over, but i wasnt sure if it had an important bend to it. It might not work, though. It has a small dent in it. (only visible in light). Ill try it, anyways. Thanks!
  8. keatonx

    keatonx Member

    So it didnt work. It should have ran great since I fixed the reed. But I couldn't adjust the carb. It was either super rich or super lean. When it was rich it made a 1 foot long pool of unburnt gas from the muffler. When it was lean in idle it would slowly pick up speed, stop thumping for a minute, then run out of gas. Oh wait, i forgot to say before that the whole time i had this thing, it ALWAYS ran with a thumping noise. It ran like it wasn't firing properly.(no, it isnt a bent rod. i checked.)

  9. keatonx

    keatonx Member

    So i got a new diaphragm and carb gasket and now it runs great, exept the dripping carb. I guess if i pull the hoses off the carb after i use the motor, it should be fine.