chain gets looser when i sit on it

[mitch_cats]

Was tightening the chain then put the bike on the ground and the chain got looser instead of tighter and than when i sat on it, it got even more lose. wtf??

 

[sean01]

are we talking about a bike or a quad???

i seen this alot on some quad models but rarely on bikes.
but if the rear of the bike is low or sagged a lot this will happen

 

[mitch_cats]

its a bike (dpro 140 to be exact).

 

[westy465]

that can happen on some bikes. on a brand name mxer, the chain will be loose on the stand, then at static sag will tighten a little bit, then with rider sag will tighten a bit more, then when the suspension goes through its stroke will tighten even more, then there will be a point at the excteme end of the stroke where it will ever so slightly loosen.

I have seen what you experienced when I worked at a not so reputable motorcycle importer in perth, its only geometry man, some frames are designed differently and yes the chain will loosen as the shock is compressed. Its go to do with the distance the swingarm bolt is away from the countershaft.

wouldnt stress about it too much. just as long as the chain doesnt get so loose that it comes off the sprocket. you would be safe to have the chain pretty tight at no sag (on a stand).

 

[bulldog93]

Chain adjustment:
• Put the bike up on a stand with the rear wheel off the ground.
• Undo the axle nut and chain adjusters.
• Push the whole rear wheel forward.
• Wind the chain adjuster back until chain tension gives you about 40mm of slack.
• Make sure the chain adjusters are adjusted evenly on both sides of the swingarm.

• Put a screw driver or spanner between the chain and rear sprocket. This will put tension on the whole set up, and allow you to tighten the rear axle nut with correct alignment.

• Tighten rear axle bolt, take bike off the stand, and sit on the bike. If you need to, get someone else to check the tension of the chain WITH YOU SITTING ON IT. You should have about 20mm of slack/movement in the chain. If you have more than 20mm slack, loosen axle and move chain adjusters back to remove slack. If you have LESS than 20mm slack, loosen axle and move chain adjuster forwards to add slack.

• Once you are satisfied you have the right chain adjustment, tighten rear axle. The simplest way to tell if you have got the rear axle torque right, is that if you spin the rear wheel with the wheel off the ground, it should rotate maybe one full revolution.. any more, rear axle isn’t tight enough, any less, it’s too tight…

- http://www.miniriders.com/bike-setup/24239-achtung-noobs-your-new-pitbike-you-set-up-tips.html

Try this. From our good friend thump*140

 

[mitch_cats]

thanks bulldog,
but when i first got it though it did tighten. Can i adjust the rear suspension so i can get it back to what it used to be.
thanks mitch

 

[brad199]

hey mitch does ur bike have a cradle style swing arm? if so thats jut what they do dude

 

[mitch_cats]

Sorry guys if ive made this a big deal but i swear i remember reading somewhere, quote: "the chain should get tighter if it gets looser throw the bike away"
any way probably a misread on my part.
thanks guys

 

[westy465]

Sorry guys if ive made this a big deal but i swear i remember reading somewhere, quote: "the chain should get tighter if it gets looser throw the bike away"
any way probably a misread on my part.
thanks guys

that can happen on some bikes. on a brand name mxer, the chain will be loose on the stand, then at static sag will tighten a little bit, then with rider sag will tighten a bit more, then when the suspension goes through its stroke will tighten even more, then there will be a point at the excteme end of the stroke where it will ever so slightly loosen.

I have seen what you experienced when I worked at a not so reputable motorcycle importer in perth, its only geometry man, some frames are designed differently and yes the chain will loosen as the shock is compressed. Its go to do with the distance the swingarm bolt is away from the countershaft.

wouldnt stress about it too much. just as long as the chain doesnt get so loose that it comes off the sprocket. you would be safe to have the chain pretty tight at no sag (on a stand).

diddnt understand this?

 

[sean01]

its all to do with the geometry of the frame.

take me all day to explain it lol.

 

[motodevo]

Sorry guys if ive made this a big deal but i swear i remember reading somewhere, quote: "the chain should get tighter if it gets looser throw the bike away"

Well you better just throw it out then!

Some bikes will get tighter as you compress the rear and some will get looser. I know with a crf50 style swingarm it gets looser. If your certain that it has actually changed from getting tighter to getting looser, whats changed or what have you changed? Are your swingarm bearings/bushes flogged out, is your chain slider worn out, are all your suspension bolts, bolt holes and bushes intact and not flogged out, is the tensioner doing its job? Also might wanna check the engine mount areas because if the engine is sitting lower than it should be it could cause symptoms like these. Me personally, if you go over it all and dont find anything unsafe i'd just set the chain slack whilst preloading the suspension and ride away