Bike not starting.

Discussion in 'Motorized Bicycle Trouble Shooting' started by Burntzombi, Sep 19, 2016.

  1. Burntzombi

    Burntzombi New Member

    Joined:
    Sep 19, 2016
    Messages:
    11
    Likes Received:
    0
    :-|| I just fished a brake in a 80cc 2stroke .Iam running a 25:1 fuel mix rich i know but figured would be helpfull for breaking in new motor .I removed motor and placed rubber shims to dampen vibration. I still have at least a quarter tank left of 25:1 bike wont start .I removed plug and of course its black.I tighten the headbolts they didn't seem lose cleaned plug bike still dosnt run .Should i get new plug? Need advise.:-||
     
  2. Slogger

    Slogger Member

    Joined:
    Sep 8, 2014
    Messages:
    545
    Likes Received:
    3
    I'll take a guess for ya. Since the engine was pulled and replaced, the wiring might have gotten tugged apart. I'd inspect the ignition wiring.
    I'd take off the magneto cover and check the blue wire is soldered on to the tiny coil winding lead and black is grounded at the core, and the connections from there to the cdi and kill button are good. Solder and heatshrink everything for reliability.
    Take out the plug, put the spark lead back on, and holding the plug against the head, walk the bike forward turning over the engine and watch for the sparks.
    Let us all know what you find.
    Good luck with it.
     
  3. Burntzombi

    Burntzombi New Member

    Joined:
    Sep 19, 2016
    Messages:
    11
    Likes Received:
    0
    Thanx for fast response will check in morning will keep you posted
     
  4. Slogger

    Slogger Member

    Joined:
    Sep 8, 2014
    Messages:
    545
    Likes Received:
    3
    And welcome aboard!

    I also wanted to mention the rubber isolation mounting thing. The consensus of opinion on the board (which is a bunch of motorbikers from way back) is that a tight, solid, rigid mounting to the frame is best. When mounted rigidly enough, the mass of the whole bike dampens out the vibes better than letting the engine dance around on cushioned mounts. The movement can cause loosened exhausts, frame cracks and all sorts of minor pains.
    That's what they say. I have mine solid, and it buzzes some but not to the point of numbing anything.
     
    #4 Slogger, Sep 19, 2016
    Last edited: Sep 19, 2016
  5. crassius

    crassius Well-Known Member

    Joined:
    Sep 30, 2012
    Messages:
    3,375
    Likes Received:
    35
    rubber mounts can cause carb problems too
     
  6. Slogger

    Slogger Member

    Joined:
    Sep 8, 2014
    Messages:
    545
    Likes Received:
    3
    Shakin it up in the gas passer, yup.
     
  7. Burntzombi

    Burntzombi New Member

    Joined:
    Sep 19, 2016
    Messages:
    11
    Likes Received:
    0
    Bike is very ridged rubber is placed on motor side only to keep some ridgednes had to deaden vibration becase choke would vibrate into closed position causeing bike to stallout still havent worked out the starting problem thinking mix mybe too rich plug is black and moist.
     
  8. crassius

    crassius Well-Known Member

    Joined:
    Sep 30, 2012
    Messages:
    3,375
    Likes Received:
    35
    do you know that choke is off when the lever is down?
     
  9. TheNecromancer13

    Joined:
    Jan 21, 2015
    Messages:
    603
    Likes Received:
    10
    You can tighten the choke lever to prevent it vibrating shut
     
  10. Burntzombi

    Burntzombi New Member

    Joined:
    Sep 19, 2016
    Messages:
    11
    Likes Received:
    0
    Well all set thanks for the help iam up and running that vibration tho iam toping out at 25 and vibration worked muffler lose any advise???
     
  11. crassius

    crassius Well-Known Member

    Joined:
    Sep 30, 2012
    Messages:
    3,375
    Likes Received:
    35
    if you have the old bone-shaker crank, you should make a hanger strap for the muffler to hold its bottom end solidly to the frame - look around the board for pics of ways to do that
     
  12. TheNecromancer13

    Joined:
    Jan 21, 2015
    Messages:
    603
    Likes Received:
    10
    Yes, but the choke is up when the lever is down, and since the choke end weighs more than the lever end, it vibrates the lever up and the choke down and turns the choke on.
     
  13. Chaz

    Chaz Active Member

    Joined:
    Jun 3, 2012
    Messages:
    910
    Likes Received:
    36
    I had this problem once and solved it with an elastic band. Many ways to fix this issue but this is the laziest I could think of. However, since cooler weather is on the way I plan to rig up a choke control for the handlebars.

    Also very important for the OP:

    " The consensus of opinion on the board (which is a bunch of motorbikers from way back) is that a tight, solid, rigid mounting to the frame is best. When mounted rigidly enough, the mass of the whole bike dampens out the vibes better than letting the engine dance around on cushioned mounts. The movement can cause loosened exhausts, frame cracks and all sorts of minor pains." - Slogger

    This is very true, in case you needed a second opinion.
     
  14. Slogger

    Slogger Member

    Joined:
    Sep 8, 2014
    Messages:
    545
    Likes Received:
    3
    Muffler coming loose.... well you can double nut the studs and put a bracket down low and tie it to the frame. That should help some.
    Still, the soft mounting lets it move. You might not see it, but it moves.
    I am glad you got it up off its butt and running better.
    Some tuning and a little more break in should see more speed as it seats its rings better and better. Tire pressure, too tight a pedal or motor chain, draggy bearings can all slow you down a hair. On these engines every little thing counts.
    My own bike picks up a MPH or so every ride now. It's faster than it ever was and it has 600 miles on it. I think I broke it in too gently.
    Thanks for coming back and telling us what's up.
     
    #14 Slogger, Sep 21, 2016
    Last edited: Sep 21, 2016
  15. Burntzombi

    Burntzombi New Member

    Joined:
    Sep 19, 2016
    Messages:
    11
    Likes Received:
    0
    Thinking of useing high temp locktight for muffler nuts is this a good idea? Also switching over mix 6oz.sinthetic to 1 gallon.?
     
  16. Burntzombi

    Burntzombi New Member

    Joined:
    Sep 19, 2016
    Messages:
    11
    Likes Received:
    0
    Thinking of getting a knm vibration kit anyone have experience with these?for now rubber band sounds like the way iam gonna go.slogger thank you you've been a big help how much how fast can i get this to go my goal is 35mph is that realistic ?
     
  17. Slogger

    Slogger Member

    Joined:
    Sep 8, 2014
    Messages:
    545
    Likes Received:
    3
    For no good reason I avoid loctiting the exhaust nuts, and use jam nuts instead.
    I used to pop the pipe off to take a peek at the rings so loctite would be a mess for me.
    The bottom support bracket and a double nut should hold it on good enough.
    I don't know what a knm vibration kit is, so can't lend any advice about that.

    After it's broken in and tuned, 35 is a fair target for top speeds. I weigh 253 (at the moment), the bike is geared pretty tall, the bike weighs 58 pounds full of gas, and I have hit 32.8 on the flat with no wind assist.
    If you gross less than 2 hundo and use the right gearing, and jet it right, and it's broken in, 35 is no big deal. You will have to hunker down out of the wind and look a little silly to find out.
    It's ok to go down even farther to 32/1 but be advised, this will richen your fuel/air mix since less oil and more gas is passing through your carb jet.
    I'd get some smaller jets (I have a bunch of them now, only need the one) or a pin vice, microdrills, and solder and pencil (you can solder and re-drill your original jet) to be ready for whatever change it needs,
    then drop the mix to 32/1, or 4 oz of oil to the gallon. Most of the old hands here will tell you that it is easier to re-jet after it is well broken in. The volumetric efficiency keeps improving every ride so your jetting is hard to finalize until its finished.
    I run Valvoline dino oil and love the smell.
    This is fun, no?
    I broke mine in at 25/to 1 as Mr Duane at Dax told me to. It was so oily, the plug was always oily, I gave that up on the third tank of gas and went to 32/1 and never looked back.
    ;) usflg
     
    #17 Slogger, Sep 21, 2016
    Last edited: Sep 21, 2016
  18. Burntzombi

    Burntzombi New Member

    Joined:
    Sep 19, 2016
    Messages:
    11
    Likes Received:
    0
    Just finshing up my second tank on my third going 4oz to 1 love this stuff the company that sent me my kit sent me two carbs jetting one is a new experience for me whats the easy but cheap way?and when should a jet bike runs nice just want that extra boost iam a bit on the heavy side 240lbs and boost bottles whats your opinion?
     
  19. Burntzombi

    Burntzombi New Member

    Joined:
    Sep 19, 2016
    Messages:
    11
    Likes Received:
    0
    Planning on taking bike on a long trip 30 miles how long agter my break in can i take this thing??
     
  20. Slogger

    Slogger Member

    Joined:
    Sep 8, 2014
    Messages:
    545
    Likes Received:
    3
    First off, jetting these carbs is easy as pie, so don't worry.
    I just bought a couple jets at a time from SBP, they sell them singly or in little sets.
    I can't give you a numbered jet size to use since that might cause you to melt your top end and come after the old moron that told you to do that.
    There are many good jetting discussions with instructions archived that can be searched up on the forum.
    I can tell you that you should go smaller than the stock, original jet.
    Before beginning the jetting process take off the float bowl, remove the float, its tang (gotta call that doodad something?) and the pivot pin, the float needle will drop out so don't lose it or tear up the bowl's paper gasket.
    Now you can grok how it all works.
    The fuel inlet is stopped off by the float needle, lifted into closing by the tang when the float floats on the gas in the bowl and rises to the right level to just feed the main jet.
    So as the engine sucks the gas out, at whatever rate, the float will lower, lowering the float needle from its seat, letting gas pour in until the level is reached to stop it off. You should check and set the float height before any jetting changes, since this will change your mixture, too.

    The first time in, you want to check and set your float height, (specs on the forum somewhere) then change your jet by threading in the new one.
    The float will stay adjusted unless the tang forks get bent and it doesn't take much to bend them, which is how you set the float height. So handle the carb gently whenever the bowl is off. The float needle and its seat, the place it closes off, must be clean. Any dirt might keep it from closing right and your engine floods.
    The jet is removed with a screwdriver, but they are so tight I just use a pair of mini vise grips to loosen it. TIP: center up the float hinge pin before putting the bowl back on unless you want a nasty gas leak.
    I didn't do this once. Gas running out, it made me feel so stupid. ;)

    The other aspect of jetting is the slide needle height.
    As you open the throttle, the slide rises lifting a needle that obstructs a passageway fed by the main jet. The higher this needle rides on the slide, the richer the mixture at the corresponding throttle position. At full throttle the needle is no longer obstructing the passage and the main jet is flowing its maximum fuel. So the needle sets the mixture from idle to 3/4 throttle, the main jet at WFO.
    Lowering the needle (by moving a circlip UP the needle (up a groove) will lean it out at low throttle openings, clearing up the blubbering and slobbering the new engines do quite a bit.
    Raising the needle (by moving the clip DOWN the needle toward the point) will enrich the idle and midrange running.

    The main jet is the full throttle/top speed mixture adjustment.
    So you want to check the float height, drop the needle a notch if it blubbers, then test the main jet. When it is good at full throttle and making good power doink with the needle to get it to idle and pull well up through the midrange.

    I like mine jetted so that I need to choke it for a cold start in the morning. Anyone that never uses the choke is running it a little fatter than I would.
    If it gives trouble in the morning even with the choke, and you need a lot of tickling to get some gas into it, it probably has a low-set float.
    Bend them forks. It's all just fun with gas toys.
    This is just an over-view, look up those other discussions on here for particulars and photos.
    Good luck with it.
    yeehaawwww brnot
     

Share This Page