I'm assuming the chain adjustment should be made with the bike sitting on the ground not on a lift with the shock fully extended. When you depress the rear suspension the chain gets tight and when the rear suspension is extended the chain is looser. It makes sense that you are shooting for the middle but my service manual doesn't say anything about this.
Also I would like to say that this system for adjusting the chain is terrible! Now I understand why there are so many stock Z400 swingarms for sale on ebay. This is definitely the worst part of an otherwise great bike.

 

I like to adjust the chain while someone near my same weight is sitting on the quad, but thats just me!!

 

KyJoe340, you are right, the Suzuki chain adjuster system sucks. I thought they were or are going to change it. The same system is on the old lt500.
To bad it is so hard to get the adjustment right on, since a properly adjusted chain/axle lets the bike work to its full potential and last a long time.


zman420, Why?

If you are using the factory specs for chain adjustment, then the bike should have NO weight on it.

Factory specs for chain adjustment take into consideration the full range of the swingarm, from unweighted to full compression.
If you partially compress the suspension with someone sitting on the bike then this spec changes.
Think about it, if you adjust the chain correctly to factory specs and then sit on the bike now the chain adjustment is not at the factory setting anymore… its tighter.

Now if you measure and record chain slack with someone on the bike AFTER the chain has been properly adjusted with no weight, you can now use this new spec for your adjustment as long the suspension sag stays the same (spring settings and the same weight/person is on the bike) when you adjust the chain.

I believe Suzuki took considerable time to come up with the best spec for adjusting their chain. I would stay with their specs no matter how much their adjuster system sucks.

Pay close attention to axle alignment. I find the marks on the swingarms are almost worthless on a lot of bikes. Check the chain/rear sprocket alignment and adjust for that. The chain should run down the middle of the rear sprocket for full power delivery and longevity.