Checking chain tension

[Guest]

I'm hoping you good people can settle a disagreement. From what I've seen online, the proper way to check chain tension is to put the bike on the centre stand and measure. My step-dad, who has been into bikes all his life, says you have to have someone sit on the bike before you measure because it stretches out the chain. Without someone sitting on the bike, my chain is a bit too loose but when I sit on the bike and measure it is too tight. What is the correct way to measure?

[John Park]

The answer depends upon the geometry of the bike's swing arm pivot. There is a point where the runs of the chain are equidistant above and below the pivot. This is where the chain will be at its tightest. The spec measured with the suspension extended is a bit of a crapshoot, and you need some slack always. If you can't find a 'volunteer ballast' sometimes disconnecting one shock will get you close enough.

The final bit of tightening as the arm swings through center does the least lengthening, so some slack at almost center is usually safe enough. Once you've established that adjustment, taking an accurate measure on the centerstand will replicate it in future.

Sometimes sprockets/mounts aren't dead center so best to establish if there is a tighter spot to work at.

[Nessism]

You can't go wrong by following the procedure as specified in the factory Suzuki service manual. Suzuki specifies the sag such that it takes account of swingarm movement while the bike is in use.

[gsrick]

The chain should be adjusted with the bike on the ground or suspended on a pit stand, so you are still using the bikes weight on the suspension. The latter is better as you can spin the rear wheel to find the tightest spot in the chain. This is at the point u[you want to adjust it. If you don't then the chain will be too taught when it comes around to the tight spot, causing sprocket, chain and possible output shaft(transmission) bearing damage. Check the chain from the underside of the chain in the middle between the front and rear sprocket. You want to set the tension at 20-30 mm of movement up and down. So technically 10-15 mm up and 10-15 mm down from it's static resting place. This is what the manufacturers call for and is taught at tech schools like MMI.

Note: This is for street bikes.

Dirt bikes are completely different, because of suspension travel. Here you would raise the bike to get the rear wheel hanging at it lowest possible travel and the tension is measured from the top of the chains path above the swing arm, directly up from the swing arm and is around double the amount of street bikes. A 2012 Kawasaki KFX450F is 52-58 mm up from the swing arm. It also utilizes the tightest spot in the chain. This is very important.

[Gorminrider]

as said above- but if there are big differences tight and loose your chain is probably wanting replacement. Take it off and measure it for stretch..(procedure is in shop manual)
Maybe you should Both get on the bike... with shock springs set at no preload to see WHY your dad is right
or some rainy day, take the shocks off (usually one end will do) and lift rear wheel to see what john park is saying....Chains are never run super -tight by the way. (Even cam chain tensioners merely stop the slack side from flopping about. They don't push very hard on the chain at all.)

I think the owner's manua( for your bike) is trying to tell you where that sweetspot is when adjusting on the centerstand but it's awkward to try to get rulers under there or whatever . whichever.. of experimental fiddling will soon give you a good feel for slack.

[posplayr]

You can't go wrong by following the procedure as specified in the factory Suzuki service manual. Suzuki specifies the sag such that it takes account of swingarm movement while the bike is in use.

when all else fails read the manual! (Not the Clymer either)