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Chain lash: What is it, what causes it, etc?

Discussion in 'Technical and Troubleshooting Torque' started by demuire, Nov 11, 2005.

  1. I've just gotten a 1993 XV250 Virago with 47000k's on it, picked it up last night and rode it home. When I took it for a test ride I didn't go past 60k's and the bike sounded fine. However, riding home along the highway yesterday, I've noticed that from about 80km/h and above (I didn't notice it at lower speeds), when I back off the throttle reasonably quickly, I can hear a strange sound, and I'm not sure what it is. Goes away when I get back on the throttle. My first thought was tappets?

    Anyway, someone suggested to me that it might be chain lash. What is chain lash? What causes it? What does it sound like? Is it bad? All the bikes I've riden past 20k's before this have been belt drive or shaft drive, so I've never experienced this...
  2. It's a service they charge extra for down at Club Hellfire.
  3. You'll have to describe it better I reckon. What's the sound like? Can you feel something odd happening to the bike as it happens?
  4. Umm... No, can't feel anything odd. I can't remember exactly what it sounds like now, I'll have to take the bike for a ride again tonight and listen to it a bit better and try to describe it...
  5. have alook at the sprockets, front and rear, if either are badly worn, it can cause the chain to jump.....
  6. Haven't looked at the front sprokets, but rear sprokets look fine. Not hooked or anything. Chain also looks ok...
  7. Chain lash occurs when you change forces through the chain.

    EG: When accelerating, the top part of the chain loop will be taught and the bottom relatively loose. Suddenly shutting off the throttle will make the chain try to reverse this and the result is the chain "flapping" for want of a better term. It gets worse when the chain is not adjusted properly.

    Also, clunking noises can occur as the chain and/or sprockets wear out, or if there's a tight spot in the chain.
  8. Hey listen Loz, I don't remember relinquishing the role of forum wise guy and village idiot to you!! :LOL:

    Classic, mate, keep 'em coming!!! :D
  9. Umm, okay. It's a rattle. I'm not sure how else to describe it, but it almost sounds like the sound you'd get if you put the edge of a piece of paper up to a fan.

    And it's there on acceleration as well as deceleration, but more obvious on deceleration. Only in the higher RPM. Tried to tilt my head around to see if it was coming from the chain (without falling off the bike), and it sort of sounds like it's coming from around where the engine is. Nothing odd happens, just the noise.
  10. There's no extra charges, just a special room off to the side for consenting members...

  11. I'd check the chain tension.
    If the chains on the way out, it may have been well adjusted when you took it out for the test ride and then stretched after a bit of a ride.
  12. Drive train slack appears to be about 35mm. According to the XV250 service manual, the front of it says it should be 30-40mm, and in the section where it shows you how to adjust it, it says it should be 15-20mm (hoorah for inconsistencies!)

    Maybe I'll take it down to a bike shop and get them to look at it...
  13. I've also done some riding on an XV250 recently, and noticed the same noise. I'm pretty sure that it is camchain rattle, rather than from the drive chain.

    The manual says that the adjuster is automatic and requires no maintenence. Hmmmm.
  14. To me it's sounding like there's a tight spot in the chain, and it's just about time for a new chain and sprockets.
  15. +1
  16. Took the bike to a bike shop today, and they loosened the chain slightly, they said it was too tight. The rattle is still there, but they said it was "normal", and not to worry about it...

    Hmm. Oh well :p
  17. Went out for dinner with some other bike mates last night, and they recon it sounds like the cam timing chain...
  18. in laymens terms its a loose chain flapping about
    the technical is ....... its a series of harmonicaly created vibrations along the chain ... caused by a by being loose which vary with the speed of the chain ... at worst it can jump teeth on the spoket or come off the sproket all together
    .. your chain .. should have between 20-30 mill movment up and down from center while the bike is resting on the ground ... ie no rider
  19. ohh and be for all the technophobes jump down my throat .... theres a lot more at play including pressure being exerted on the chain from the engine sproket /from aceleration deceleration etc but u get the point iam sure