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Mossriders lessons from the road 2


mossrider

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Chain tension.

We've talked about this before. More is not always better. I get bikes in my shop all the time with chains set like piano wire. Set your clean chain tension according to the manual on a stock bike or even looser if you've raised your rear suspension via a longer shock or different linkages. In order for a motorcycle to work correctly it's chain must have the correct slack. An over right chain will wear out parts and can be dangerous. It can hinder or prevent proper shifting and wear or even damage the transmission. It can bind the suspension which can cause loss of traction during acceleration or under braking.  Because of geometry a chains slack is not a static figure, it varies as the swingarm moves through its arc.

Not sure about all this? Check your chain tension with your bike on it's side stand. Now have your fat neighbor or me sit on your bike and check the chain tension again while the suspension is compressed. See the difference? Use the owner's manual or maintenance manual they are not your enemy.ūüėĬ†

Here's a quicky that demonstrates,

Ride safe. 

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Great advice Moss. That’s how I set mine too, disconnected the shock and raised the swing arm to find the tightest point. 

Ed

"Do not let this bad example influence you, follow only what is good" 

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Northstar01

The manual suggests 51-56mm of slack for stock suspension. I have a K-Tech razor R that is 10mm longer. How do I know how much slack to add? Should I just stay on the high side of the suggested slack?

I also have a Robem linkage that changes the angle of the swingarm. How would that impact my slack?

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23 minutes ago, Northstar01 said:

The manual suggests 51-56mm of slack for stock suspension. I have a K-Tech razor R that is 10mm longer. How do I know how much slack to add? Should I just stay on the high side of the suggested slack?

I also have a Robem linkage that changes the angle of the swingarm. How would that impact my slack?

Put your rear end (the bikes not yours) up on jack stands so the swingarm droops with no weight compressing it. Take the shock loose on one end. Swing the arm through its arc w/o the tension of the shock this will show you what your chain tension is. Now adjust it so it always has 'some' slack, say around 15-20mm at it's tightest point. You'll find you are well over the manuals numbers on a modified bike. What bothers folks is that it will appear to be too loose at rest when in fact it is not. Again when finished try the compression test with a load aboard, you'll see.

A modified bike with increased swingarm angle will require more slack than an unmodified bike. This is because the chain tightens as the swingarm approaches alignment (that point where the rear axle, swingarm pivot and front sprocket align, also the furthest distance the sprocket faces are apart)

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This is what I've just told to a friend of me. He just got his motorbike license an came around with his freshly bought Honda CBF 600 PC43.
I was touching his new DID 525 VX with my foot, lol it was sooo tightened. Without rider, on the sidestand maybe 15mm slack, with him on the bike maybe 5 mm if you press/pull hard :D

 

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I don't trust the manuals either.   The best way to know where your chain slack should be set is to either get the fat neighbor or pull the back end down some way to get the counter shaft sprocket, swing arm pivot, and rear axle centers in line, That is the point where the rear wheel is furthest from the counter shaft and thus the tightest spot for the chain.   Now adjust the chain to about 1" or 25mm play.     Release the bike to allow it to sit normal, measure the chain play and make a note so you know how much play HAS to be in the chain to avoid being too tight.  

I'd rather run loose than too tight.   Kawasaki's manual for my KLX250 says 1.4-1.8" slack.  My check says if I do that I will have that banjo string you speak of when those points align.   I measured around 2.5" after setting up as I did, so I run around 2.0-2.5 " play so I know I'm good.  

My Zephyr 550 had a chain with a perforated  side plate.  I broke a side plate running too tight, running what the manual recommended, it now runs enough to know it isn't too tight.   With a good chain it will not derail under normal use if loose.   Just look at the slack in a motocrosser's chain.

I just have little faith in the manuals.   I doubt if they actually do a proper measure to know for sure, probably printing the average values.   

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I use to run my chain really loose, see picture both top and bottom is loose. Right under footpeg is little wheel chain rides on when suspension is unloaded. Same way dirt bikes used to have little wheel under it. 

 

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A decent chain would never flex enough to derail, so no problems with a bit of slack like that.   Better than putting strain on counter shaft and rear wheel bearings, possibly damaging either the bearings or - worse yet - the cases.   

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