I just traded for a 2000 400EX and was wondering how to adjust the chain tension. I didn't get an owner's manuel so I am kind of going blind at this aspect.
Losen the allen bolts on the rear of the axle carrier, stick something like an allen wrench into the slots on the left side flange and pull backward. The aluminum housing will rotate and since the axle is off center in it, the axle will move rearward and tighten the chain. Retighten the allen bolts. It's been that way on all of the larger Honda 3 and 4 wheelers I've ever seen.
Seems like we get this question several time per month. You bought a used machine and the previous owner doesn't even know where the manual is. You think they ever did any maintenance on it without a manual????
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So. Calif. Deserts and Mountains!
Desert- 450R
Trail- 400EX
Mountain Technical Trail- Rancher 420 and 350
Kids- Two 250EX's, TRX 90
Dual-Sport Bikes- KLX250S, XT225