My thatsdax engine dies or died on me : /

Discussion in '2-Stroke Engines' started by Dr. Doom, May 1, 2010.

  1. Dr. Doom

    Dr. Doom Member

    I've had this engine for quite a while and filled the gas tank for I don't know how many times. The problem I have is that recently overnight my bike noticeably lost power and speed on the straight-aways. I recently changed the sprocket from 44T to 36T and understand the concept with the speed change. It was great I went nice and fast but basically after this change this problem occurred! This bike started up for me no problem, I rode around with impressive speed, then I loosened the throttle and it was as if later I couldn’t go that fast anymore as before again. I thought it was a fluke but on my way back home it became so weak I had to start pedaling.

    I cleaned the wires, cleaned my original spark plug, messed with the gas on/off, and then later cleaned the air filter. Problem did not fix when I tried to start her up again. All I got was her having the hardest time starting while making these loud unhealthy popping noises occasionally. When it finally started the engine was running only when the clutch was pulled in out of gear. I checked gaskets after that but all looked fine. Does this sound familiar to anyone who may know the answer to an easy fix?
    Last edited: May 1, 2010

  2. Al.Fisherman

    Al.Fisherman Active Member

    Have you checked fuel flow to the carb (both external and screen filter in tank) remove the screw below the fuel bowl, and watch for flow? Have you checked the compression....I'd start there. Popping noises brings to mind timing. Check the key that holds the magnet in place. How is the fire to the plug?
    Last edited: May 1, 2010
  3. Dr. Doom

    Dr. Doom Member

    No. What kind of tool do you need to check for compression?
  4. G-Superior

    G-Superior Member

    Go step by step starting by the cheapest
    Clean the carb. when the jets gets cloged up the reduce engine performance really bad
    Clean exhaust. when they get clogged up they can reduce engine power by over 50%
    change spark plug(the chinesse one is junk!) get a NGK or a similar high quality plug(dont forget to gap it propely!)
    Get a new high quality plug boot and wire. The chinese one is worser then nothing:whistling:
    Buy or make some HIGH quality gaskets because the chinese one can fail and destroy your engine(the carb manifold one especialy because if they blow false air entrance will make your engine run lean and seize up! and also the exhaust one!)
    IF THIS list dosent do anything to the engine then ask someone(or me:D) or search in this forum for old threads because they can be very helpful!
    Good Luck
  5. G-Superior

    G-Superior Member

    to check for compression just lift your wheel off the floor and try to turn the engine over(with the plug screwed in but the wire off so it will not fire up and injure you!)
    If is hard then its got compression(can also be seized if it is really really hard)
    another way is to get the plug out and turn the wheel and put your finger in the plug hole, if it sucks the pushes it out then you got some compression
  6. Al.Fisherman

    Al.Fisherman Active Member

    Ummmmmm maybe you need to place the engine back in the box and return it....all kidding aside, the compression is checked with a compression guage/tester.

    There are other places that you can get them cheaper. I'd have one around, it's a very important tool for internal combustion (non diesel) engines. If it has a spark plug you need one.
    Last edited: May 1, 2010
  7. Al.Fisherman

    Al.Fisherman Active Member

    Yes SOME compression, but these engines won't run on just some compression. I'd venture to say you need at least 90# minimum. And to tell you the truth, a person not familiar with compression or a tester won't be able to tell if there is enough to begin with. Second, compression at low RPM as spinning the wheel is nothing as having the engine turning over at 2-5 MPH.
  8. G-Superior

    G-Superior Member

    I can check any engines compression by just turning then over, but I forgot to say that i have quite a few years of experience and lots of engines trou my hands :rolleyes7:
    you will get better over time:whistling: but a compression tester will help a lot, my costed something like 20$
  9. AussieSteve

    AussieSteve Active Member

    Compression testing should be done at 'normal cranking speed'. On these bikes, that's pedal-starting speed. With a stock (non-slant) head, you're looking at about 95psi, as Ron says.

    The real point that I wanted to make, though, is that you say you cleaned the original spark plug.
    That implies that you haven't tried a new plug. Do that first. Try an NGK B5HS or B6HS.
  10. Check your throttle cable, it may not be opening up you carb slide all the way up,take off air cleaner and turn throttle, is the carb slide going all the way up?
  11. Skyliner70cc

    Skyliner70cc Active Member

    I've got same problem on a dax I bought new last September and just installed 3 weeks ago. I'm suspecting an airleak and haven't had time to track it down.
  12. KCvale

    KCvale Motorized Bicycle Vendor

    Easiest checks. Pop of the air cleaner.
    As mentioned, does the throttle cylinder go ALL the way up on open throttle?

    This also allows you to check the choke opens and closes properly.

    I know, sounds mindless, but I left my choke half closed once and started with all the other stuff first.
  13. Dr. Doom

    Dr. Doom Member

    I have the answer/solution

    Alright I checked everything and the main symptom I can find is while I pedal the engine it'll respond back with threatening powerful popping noises spitting out smoke from the carb.

    The solution was to get a new sparkplug. PROBLEM SOLVED. I had no clue a sparkplug could fail or simply turn into **** that dramatically over a day. I checked it and thought it was good, but replaced it and boom. No problem anymore. Before the engine may start but would die and i thought everything was dieing. No way... With how everything was i didn't believe it at first. Sparkplug is a big big BIG influence on the engine, i thought it was just there to start it ~nope It's more than that
    Last edited: May 8, 2010
  14. AussieSteve

    AussieSteve Active Member

    Good one, glad you sorted it out. As I mentioned earlier in the thread, it's a good idea to swap plugs first. Partly because it's easiest.
    Sometimes a plug can look good, but can have a crack in the ceramic deep in the plug body that allows it to short. Sometimes it sparks OK when out on the head, but shorts under compression, causing missing.

    For that reason, if you ever drop a plug on a hard surface, ie concrete, it's a good idea to replace it.
    Last edited: May 9, 2010