Engine Trouble Will not Idle, At All!

Discussion in '2-Stroke Engines' started by Lloyde, Apr 2, 2016.

  1. Lloyde

    Lloyde New Member

    So here are the circumstances that lead to the problem. Just before it started getting real cold last year I was riding my bike and got the engine to run like normal, then about a 1/2 mile from my house I look down to adjust the Air Intake to get more air and run a little smother. As I am looking down my engine gives a POP, and I see the Cylinder Head jump up at me and the engine dies. I do the safe thing and turn around, when I get back home I remove the bots holding the Cylinder Head and find it is is 2 pieces! (see pic) As I have come to understand this is actually a somewhat common occurrence.

    After doing research (and waiting for it to get warm again); I ordered a new head and CDI coil, cleaned the piston, cleaned/gaped the spark, and a couple other things

    I got the new parts and could not test them for months because it got to cold and snowy/icy. But now it is warm and I was testing the other day. It took a couple minuets but it did start again, yet it did not sound like it used to. When I got to a stop sign I had pulled in the Clutch, released the Throttle to make sure my phone was still in my pocket, and the engine DIES!

    I jump off the bike and poke around it with a questioning look, I jump back on and start moving again it starts back up, but the silly thing Will Not Idle, and it takes a while to get started each time.

    New (?) problem, trying to start the engine it will sometimes Backfire (?), not sure if that is the right description, but a small white poof of air will sometimes come out of the Air Filter on the Carb.

    Any help with this is much appreciated
     

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  2. Timbone

    Timbone Active Member

    The obvious place to start is to keep tightening the idle screw on the carb until you can find the magic place where the engine will hold an idle.

    If the idle screw has no effect then you have a different problem. Could be a fuel line issue, maybe a bad float in the carb, etc.
     
  3. Greg58

    Greg58 Member

    Did you check the new head for flatness? Most can use a little clean up. I tape a piece of sand paper to a flat glass and sand the head surface in a circular motion, its surprising how untrue a head can be. I do this to the cylinder and head before I ever install the engine. All heads are not the same, some have squish bands and some don't. The former runs a lot more efficient.
     
  4. Lloyde

    Lloyde New Member

    Hmm, now that you mention it the new head did have a couple of indents on the area that should seal onto the Cylinder Head. I'll have to try the sandpaper trick, what grit sandpaper did you use?

    No fuel line issue, the Carb works perfectly (other than that odd puff of air thing), and I tried the Idle Screw already. All the way in, and out.
     
  5. Hello Moto!

    Hello Moto! Active Member

    I resurfaced mine with what sandpaper was available at the time. IT was 600 grit and it worked nicely. Definitely not to rough and the finish was very smooth in my opinion. I also made a new gasket out of gasket material as I heard you should not reuse the aluminum head gasket. It's really quite simple to do.
     
  6. Greg58

    Greg58 Member

    I start with around 200 grit then go to at least 400, the 600 would be good and smooth. You can also do a compression check, anything between 80 to 120 psi for a stock engine.
     
  7. Lloyde

    Lloyde New Member

    hey, the engine is backfiring. I know it is because I can smell fuel in the puffs of air coming out of the Carb now. Do I need new jets, seals, or what?
     
  8. Greg58

    Greg58 Member

    Try moving the clip down a notch on the needle, I had one nt that would not idle with the clip in the top slot. Either the needle was too long or the jet was under sized, moving the clip down a notch let me adjust the idle with the screw. What you are seeing is blow back coming from the carb, since these engines don't have reed valves that seal after the fuel is drawn down in the crankcase some will blow back when the piston cycles.
     
  9. Lloyde

    Lloyde New Member

    There is a LOT of blow back, as in I can feel it moving my pants as I try to get the bike started.

    I moved the clip on the needle down one notch (it is now on the bottom notch), and it is puffing a lot worse so I may move it up to the second notch.

    If it is the jet then I am thinking of getting a jet kit (
    http://www.gasbike.net/products/5mm-nt-carburetor-jet-kit )

    I currently have a 36T Sprocket on right now getting a Max of around 24mph. I can't entirely say why, but I think it was going faster with the 44t Sprocket that the engine comes with. Pain in the Arse to put on, but as far as I can tell completely worth it.
     
  10. Greg58

    Greg58 Member

    A couple of questions, have you checked the head for flatness? If you can feel the compression leaking between the cylinder and head that's a big problem. Have you turned the head 180° ? Sometimes the head will seal better, if the plug wire is long enough its worth a try. Once you get the head sealed you can tune the carb.
     
  11. Greg58

    Greg58 Member

    24 mph is really low, sometimes on a unmodified engine the smaller sprocket keeps the engine from reaching the needed rpm to produce the maximum horse power. The guys that reach the higher speeds have a good bit of improvements done to theirs. Just as a example I have a straight plug head on one of my 48cc engines that has been shaved .040, ports cleaned up and the piston skirt trimmed to clear the intake port at tdc, it will do 30 plus on flat roads with a 44 tooth rear sprocket. I have another engine that has a angle plug head with a nice squish band with porting and piston trimmed that has reached 32 mph on the same bike.
     
  12. Hello Moto!

    Hello Moto! Active Member

    I resurfaced the head and made a new gasket and I still don't feel like my engine is running 100% I'm almost wondering if my crank case has a minor leak. There's a spot where the gasket isn't seated right. Not sure but I can only get to about 27mph and it seems boggy any where after 15mph. Maybe our problem is similar lloyde.
     
  13. crassius

    crassius Well-Known Member

    some motors are just slow - I'm thinking bad port timing by some factories, or highly polished cylinders not getting a good seat of the rings - a lot of the old H2 motors were that way

    never forget to check case bolts and suchlike for seepage tho
     
  14. Lloyde

    Lloyde New Member

    Yes, I have checked for flatness. And I sanded the Cylinder, Cylinder Head & Piston so they all should be flat & smooth now. I'll try making my own gasket, and attempt turning the head 180*. I say attempt because my bike frame is a little tight on space.

    When you say Smaller Sprocket, are you talking about the Rear Sprocket, or that little 9T/10T Sprocket that is Part of the engine itself. I don't count myself as stupid, but I like clarifying when there are multiple bits & pieces that have the same name.

    By that do you mean to simply say to make sure everything is tight? I remember trying to take the Crankcase apart at one time, but for some reason I could not get it apart even though I was watching a youtube video on how to do it. And I am confidant that I put everything back in the correct place.
     
    Last edited: Apr 15, 2016
  15. Greg58

    Greg58 Member

    I was referring the 36 to the 44 on the rear, depending on the weight of the rider the 36 may be too tall of a gear. Remember the more teeth on the rear the lower the gear, more teeth on the front the higher the gear.
     
  16. Greg58

    Greg58 Member

    One good way to check for a good seal is to spray the head gasket with paint on both sides and torque the head down, then removed it and look for spots on the head or cylinder that doesn't have paint or the paint is very thin. We used to spray metal head gaskets to help them seal before permatorque gasket were available for auto engines.
     
  17. Lloyde

    Lloyde New Member

    OK since the last comment, I made some new seals (upper & lower cylinder), tried turning the Cylinder Head 180* (could not do it because of the frame), Somehow I have lost one of the bolts that go in the Gear Case Cover (could not find it, so I made a replacement using a longish bolt a couple washers and a lock nut), i'm about to try it out and i'll get back to Y'all weather or not it is working.
     
  18. Lloyde

    Lloyde New Member

    OH MY GOD! DX I decided it would be a good idea to check on the Spark Wire Loop Set - Magneto, because I had heard that there is sometimes a problem with its wiring. And Guess What!!! the 12V Generator that I had installed last year was literally, . . . . well I'll just attach some Pictures. The First picture is a stock photo from Gasbike.net, The Second picture is after I took everything out of the Magnet Electric Cover, it ain't pretty.
     

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  19. Lloyde

    Lloyde New Member

    BUT! The Good News is after I removed the broken 12V Generator, I put the cover back on and tested her out. AND SHE IS ALIVE AGAIN!!!
     
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