Chains Bike chain keeps pulling off

Discussion in 'Transmission / Drivetrain' started by Zalaki, May 17, 2011.

  1. Zalaki

    Zalaki New Member

    I am not sure if the engine is pulling it or if maybe the chain isn't getting tightened enough, but I am doing my very best to tighten that **** like no tomorrow.


    what is the ratio of gas to oil for a 2 stroke? like I said in my intro im new, don't judge hahahaha ;p

  2. adrian101

    adrian101 Member

    If it is a new engine and you're breaking it in then use 16 to 18 parts of gas to 1 part oil. It will show on the oil bottle of how much oil to add if your doing 16:1 or 18:1

    As i'm finished with break-in period so i use a 32:1 gas/oil mix.

    You can tighten the chain by pulling the back wheel up higher in the wheel slots where you tighten the nuts that hold the back wheel on if you know what i mean?.

    are you talking about the chain to the engine?
    or chain from the peddles to back wheel?
  3. retromike3

    retromike3 Member

    check engine mounts

    The first motorbicycle I owned eventually shifted its position when I hit the throttle, unfortunately this caused my chain to loosen and jump off. The next thing that happened was that the chain got jammed between the cog and the spokes on the rear wheel. This was not a fun occurrence, especially since it happened in a tunnel when I was going downhill at really good clip. Since then, I go with longer mounting hardware and I double bolted all the studs. It seems that with these two cycle motors that if it can loosen up it will. in fact I've had parts on my bicycle loosen up that I wouldn't even consider rattle off.

    So think double bolts, blue lock tight and vigilance.

    Last edited: May 17, 2011
  4. Zalaki

    Zalaki New Member

    I have been riding it and the previous owner rode it very little but I am going to try going 32:1 for the gas now.

    I am talking about the motor chain to the tire. I unbolted the screw which holds the chain up, forced the chain up to tighten it then secured the screw/nut as high as possible and as tight as possible.

    retromike, ya that happened to me the first time, it got jammed and it took me forever to try and pull that bad boy from being stuck :/
  5. adrian101

    adrian101 Member

    So its still coming off even thou the chain tensioner is at its highest point?

    You may need to take some links off the chain. Make sure to check if the sprocket is 100% completely straight, If it is uneven/not straight it will spit the chain off.

    Also check if the back sprocket is lining up with the drive cog on the engine.
  6. retromike3

    retromike3 Member

    horizontal dropouts

    I got tired of having my chain tensioners fail and I welded track bike dropouts on my old Giant mountain bike frame. I also had to weld a rear derailleur hanger on the pedal side. now if the chain stretches a bit I just pull the rear wheel back a bit.

    I have yet to se a good quality chain tensioner, but my standards may be a bit high for the average guy.


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  7. olow

    olow Member

    sounds to me that the chain tensioner is looseing first off u said u set the roller all the ways up well this could be part of your problem as the roller comes down and loosens the chain.what ive done and it works good is get 2 new bolts and nut for the bottom of the tensoer only when u do get the heavey duty ones that torgue high they really get tight these are usually finer threads second tighten them so they are snug and i get a hammer and knock the the tensioner back till the chain is pretty thght then tighten the new bolts real tight with 2 wrenches even if u have to hammer one wrench with a hammer this works as i very seldom have to redo most of all check the tension on the chain freakently
    try this and let me no
  8. retromike3

    retromike3 Member

    maybe its more than the tensioner

    I think that your rear cog may not be centered as well as it should be. this will cause the chain to get slack and tight every time the wheel rotates. If you tighten the chain when the cog is closer when it goes farther out it will fail at the weakest part first. That looks like the chain tensioner. I had problems with mine even though I have a hub adapter and bolt my cog directly to my rear hub.

  9. motorpsycho

    motorpsycho Active Member

    i would check the chain/sprocket alignment.
    if the chain keeps jumping off (which is the way i read the post) i bet the chain and sprockets are out of alignment.
  10. badlandkustoms

    badlandkustoms New Member

    Iv got the same problem with mine, Everything is in line and works fine till I try to start the eng. I have been checking everything I can think of as to why this keeps happening, Maybe I will get to ride this thing soon
  11. badlandkustoms

    badlandkustoms New Member

    Well I went back over everything, I readjusted the chain and made sure everything was tight and in line. Seems to be fine now, I just got back from a 7 mile ride:D
  12. Lazieboy

    Lazieboy Member


    I use a hose clamp to secure muffler to frame to avoid motor movement., I also have my tensioner mounted from top so roller wont lose adjustment, its bottomed out.

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