Engine Trouble All put together. I just can't start it. [ spark fluids ]

Discussion in '2-Stroke Engines' started by keithfmuta, Jul 12, 2007.

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  1. keithfmuta

    keithfmuta Guest

    I have just put together my 48CC motor and all appears to be well. I have two problems. It won't start when I release the clutch and the more I twist the throttle the worse it seems to be. Also how much play should the chain have. If I have it tight it comes off the cog on the rear wheel. But if it is loose enough not to come off it seems too loose and hits the chain guard. I am new to this and I am busting to get motoring.

  2. thatsdax

    thatsdax Guest


    Do you have spark? Also..Did you taper the rear sprocket before installing? Let us know...Thanks..
  3. rcjunkie

    rcjunkie Guest

    It won't start with a full choke, especially on a new engine.
    Use choke to get a good prime in carb and then move choke to 1/2 way.

    Check spark plug gap. Not unusual for plug tip to get smashed into center electrode when in the box being shipped from China to USA and eventually to your home.

    Throw away that stock factory kill switch and replace it with a quality one that won't fail. I have had 4 switches (factory) fail and prevented me from starting because they were stuck.

    You have to find the sweet spot on the throttle and occasionally on the choke on a new engine/first start situation for it to fire. I usually vary both while pedalling down a hill to keep speed up.

    You may also want to squirt some starter fluid into the foam airfilter assembly just before you pedal to start (act quickly, since this stuff evaporates quickly)

    Chain should have about 1/2 inch slack in it. If tension is not consistent, your sprocket is out of round and not centered properly.
  4. Herrmanator8

    Herrmanator8 Guest

    i never use the choke to start it, the engine is so small that it needs air, i only use it to shut it off. starting fluid wont work either because it goes into the crankcase first and by then it has already dissipated... choke off, petal up to about 6 to 8mph and release the clutch and petal for your life and eventually itll kick over :grin:

  5. rcjunkie

    rcjunkie Guest

    Uh? Starter fluid doesn't disappear..the crankcase is sealed in two stroke engines and it will eventually find itself into the combustion chamber to be ignited. It works well for new engines and is an easy way to rule out ignition problems. If the engine won't fire on starter fluid (ether) than you have an electrical issue. If it fires on ether but won't stay running then you know you have a fuel delivery issue.

    As for choke? I do not understand what size of engine has to do with choke or need for air (air requireements). All engines regardless of size need about 14 parts air to 1 part fuel for the mixture to ignite. However, a cold engine needs a mixture that is richer than the usual 14:1 (stochiometric ratio)..a choke is an easy way to achieve that mixture and start a cold engine. Our chokes do not completely block off airflow..just partially...most of the engines do better on partial choke but my newest one surprised me and will run on full choke.
  6. davidsis

    davidsis Guest

    Wont start

    Starter fluid may blow your engine. Take the kill switch completely off and get it running before installing. Check to make sure you have a spark. Take the kill switch completely off and get it running before installing. The kill switch. Use full choke, and full throttle. You will probably never read this because you are probably off rideing. Make sure you get that chain issure straightened out before you mess something up. I always want to just take off as soon as I make a bike. Rode rash hurts.
  7. kfss

    kfss Guest

    Trouble Starting

    I had the same problem last year when I bought my first motor kit and installed it. I noticed I was getting spark maybe one time spark per who knows how many rotations of the engine. After much talking with the guy who sold me the kit, I sent my CDI in and had it checked out. It got sent back to me and it had checked out OK.

    So I installed the CDI again. Still no start. I was about to get a refund from the guy I bought it from but I decided to try one more thing. I popped the magneto cover off of the left side of the engine. When I went out to try it again I had a vehicle pull me (don't worry, I was very safe. I was on an airport flightline!) and I noticed whenever I popped the clutch, that spinning thing inside of the magneto wouldn't move very much at all. Then I stopped and pushed in on it and then turned it about 10 times with my finger. The next time I went out to try it, it worked! :razz:

    No more problems.
  8. spunout

    spunout Member

    Welcome to MBc. as far as the chain goes...1/2" to 3/4" play between cogs is standard around these parts.
    learn to use the search (upper left hand cormer of these pages). i entered "chain tension" picked the 'search for all terms' option and got 43 hits.
    Happy :mrgreen:
  9. fairracing31

    fairracing31 Guest

    Twist the throttle and it gets worst. Mine did the same thing when I put it together. What I found was the Intake manifold had a vacum leak. Make sure it's tight and the carb, if you have to make a new gasket for it. I used a roll of gasket maker from auto store.
  10. rcjunkie

    rcjunkie Guest

    Hello again. A previous poster said that starter fluid may blow your engine? I wish to point out that is highly unlikely. Starter fluid is very safe to use in gas engines. Its use in diesel engines is another issue since diesels don't have a throttle to restrict airflow and can "run away" with ether use.
  11. fairracing31

    fairracing31 Guest

    As a auto tech, using starter fluid in anything is not a good ideal. I've seen so many damaged motors by starter fluid, and YES you can blow a motor with starter fluid, I've done it myself!! You are better off using WD40, try it.
  12. drimpact

    drimpact Member

    I have used WD40 to start my 2 cycle Evinrude Outboard motor on many occasions. All the old mechanics I learned from called starting fluid "Bent Rod in a Can". Starting fluid works, but please use sparingly if you like your motor. :sad:
    Last edited by a moderator: Dec 15, 2015
  13. gone_fishin

    gone_fishin Guest

    since i use a zippo anyways, i just squirt a bit of lighter fluid in there...sometimes i add a squirt of 3-in-1 to assure a dry motor doesn't wipe itself.

    i only do this when i need to know if an engine will fire...i never try to run it on that mix.
  14. fairracing31

    fairracing31 Guest

    Here's a tip to check spark instead of using a screwdriver in the plug wire and trying to crank the motor. Go to your local auto parts store, for about $3.00 get a spark plug tester. It's a spark plug with aligator clips, you just use your plug wire on the test plug and clip it to a ground on your bike, makes it alot easier . Or if you are as cheap as I am, use a old spark plug and buy a bag of aligator clips for like $1.00 and solder it to your new test plug.
  15. rcjunkie

    rcjunkie Guest

    Please educate me. How can ether blow a gasoline engine and how is WD-40 better? I would like appreciate some insight into the matter with the actual mechanism of action of how this occurs in a gas engine THANKS!

    PS Example of why ether is bad for a diesel engine: Ether can damage a diesel engine in the following ways: If ether is sprayed before glow plugs are engaged, it is possible for it to ignite and blow the head off. If too much ether is sprayed into intake while cranking, the diesel engine can start and run away..meaning over rev engine well past redline. Ether can cause glow plugs to swell and they can break off if trying to replace them..resultant pieces can cause engine damage.
  16. fairracing31

    fairracing31 Guest

    Ether is more explosive then gasoline and diesel fuel. The biggest problem is that people use too much. I have seen pistons with hole's the size of golf balls,bent rods, head bolts streched, burned valves, it's just nasty when you load ether on top of the piston. WD40 is less explosive and you also add luburcation witch makes it way better for 2-strokes and diesel. Ether can do big time damage to piston rings and cylinder walls because it washes out all your lubercation. If you are wondering if you are getting fuel? Just pull your plug out and see if it's wet, Try my tip to check for spark. It doesnt matter if its a 4-stroke,2-stroke, or diesel, use too much you will damage your motor,you may not notice it right away, second, it just robs your motor of lubercation. At are shop, you will find no ether.

    Fair - you can go into you profile, click off the "Disable BBcode in this post" and then quotes, bolds, underlines all work. If you leave it off, makes pic loading a breeze too.

  17. rcjunkie

    rcjunkie Guest

    Ok, thanks for the info. I'll stick with my ether since I have been using it for 20 years without a hitch. A little shot is all you need and I agree that using too much can be harmful.