Ive been riding and racing for many years and always went with the 3 finger rule from the back bolt of the front chain slider (top of the swing arm) to the bottom of the chain. Recently within the last year I heard Trey Canard saying they were using more like 4 fingers or even more because 3 was not enough and will cause the rear swing arm to bind. My owners manual on my 23 crf450 does state somewhere between 2 1/4" - 2 3/4" chain slack, which seems loose and always makes me a little nervous but honeslty I do notice a difference in how the bike feels on track so I definitely think it needs to be looser than my old method. Anyone have a tried and true fool proof method to chain adjustment. Also is anyone out there hyper fixated on adjusting their chain at least every ride, sometimes twice in a practice day? I sort of obsess over it and always have dark thoughts in the back of my head about it snapping from being too tight or derailing from being too loose.
You can pull the shock and raise your back wheel to find the tightest point. Set it a tad looser than that, install shock and then take your measurement with your bike on the stand. That should be your new measurement to go off of.
My 04 cr250s measurement in the manual is like 25mm which seems extremely tight, but as you go through the stroke the chain hardly tightens. My 23 ktm needed 68-70mm
Good info. Thanks Brother. Also when I measure from the center of the chain should I push down on the chain until its tight to achieve my bottom measurement, then pull up until its tight to achieve the top measurement? Or is simply letting it rest to achieve bottom measurement, then pulling it until slight tension to achieve top measurement more suitable? Because that can change the measurement quite a bit
This is a good way to do it. Ridejbi also has a good vid but I couldn’t find it
https://youtu.be/au5-27pkoDU?si=9hirvqUpVCZGjsM3
I did this for my young teenage son who was doing most of our bike maintenance at the time. Once you find your setting make a small block out of wood or I use composite deck board scraps. Slide the block in behind the chain guard. We made a few of em. We have one in shop, trailer, and track box. Just makes it super easy.
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Don’t overthink it. Get a piece of plastic that is 2-3/4” and use that as a measuring tool. What chain are you running?
Primary Drive O ring
This is the only accurate way to get it right. And it needs to be redone if you change gearing, a different diameter (tooth count) sprocket will change the measurement.
I use three finger, have big hands. It’s worked for me. I’ve measured and was close enough. For grins I bought two of those red plastic chain gauges, one for my Honda, one for my KX. Three fingers is about in the middle.
The below pic shows the fool proof method. Simply mark a square to the desired measurement, slide it up to the rear of the chain slider, lift up on the chain until the bottom of the chain reaches your mark, that simple! This will give you the perfect chain slack every time. In my experience the owners manual has the correct chain slack but I always check it while doing new bike prep. I check it by moving the swing arm through it’s travel with the rear shock removed and seeing if the chain remains with some slack in the tightest part of the travel
Pro tip: On track days where it’s really deep or has some muddy conditions, be sure to add additional slack. I like to add 1/4” of slack if mud is packing in my chain, countershaft, guards, etc.
If you run your chain too tight, you can crack your rear hub or put too much load on your countershaft bearing. This can wreck your cases when the countershaft bearing comes apart. I have had both of these happen to me over my riding career.
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