Chain tension?

[littlewing78]

Hey all.  I got my first bike about 2 months ago.  I got a 1999 KX 500.  Its big, ugly, and oh so fast.  Great beginner bike huh.  Last week I had a little wreck and popped the chain off.  We got it back on easy enough but it was really loose after that.  I have tightened it up but I don't know how much slack to leave in it.  I don't know what point to measure the slack at either.  I still haven't gotten a manual for it.  Thanks for you help.

[littlewing78]

Never mind I just found on here. 

[littlewing78]

Ok I think I have it set right but I want to be sure.  Specs say 50-60 mm from swing arm to bottom of chain.  I set it at 55.  That's with the bike on the stand and the rear wheel off the ground. 

[Friar-Tuck]

Hey 'lil78
 My FSM is '88 up. However the clymer  has the following on all '83 to '87 125,250 & 500
   Push the middle of the upper chain run up away from the swing arm.
Measure free play between the chain and the swingarm at the rear of the rubber swing arm protector
  clymer M-447 page 79

  Free play measurement, table 11  pg.106  50-60 mm or 1.96" -2.36"

 Bike on the ground using sidestand  no rider on the bike.

[Polar-Bus]

Always remember a golden rule, if you're not sure, run your chain loose ! I've seen so many people unknowingly run a chain too snug, and if you have a scenario where moist sand or dirt gets packed into the rear sprocket teeth, you can possibly explode the rear wheel hub from the chain slack tightening as your swingarm travels up through it's suspension stroke. FYI your front to rear sprocket center to center distance lengthens as your swingarm travels through the suspension stroke. Years ago when I was hardcore racing, I used to have 2 people sit on my bike to compress the suspension and get the swingarm parallel with the ground, then add 5/8" of chain slack for a safeguard. Nowadays the facrtory recommended specs are pretty safe.

[motodog]

Run your chain slack no tighter than 55mm measure from the back of your chain slider on top of the swing arm to the bottom of the chain - with the bike on a stand (rear wheel off of the ground).  Works great - been racing KX500's since 1985.

[littlewing78]

Thanks for the help.  I have it set right at 55mm the way you explained it motodog.  Maybe I will go loosen it a tiny bit.