drive chain and sprockets

[andyb]

So, chain recommendations? Middle grade quality.  I don't really run it too hard, or race or anything.

Sorry for late info and it won't be applicable to sovrin other than as something to mentally file.

Drag racing puts a given stress on a chain, but it's absolutely not as much as hitting bumps does...most of the stress comes from the chassis sagging on the launch.  Because the countershaft, swingarm pivot, and rear axle all move in such a way that the chain gets tighter as you compress the suspension, the hardest thing for a chain to cope with is the stress of hitting a sharp bump and having the chain be the limiting factor in how far the tire moves up.... this is why a too-tight chain will get very poor life compared to a chain that's too loose by the same margin.

If you picture those three elements as the triangle that their points describe, the chain must wrap the entire way around the triangle (obviously).  As the swingarm comes up, the three form a flatter and flatter (or shorter vertically) triangle, but that makes the distance around longer, which stresses the chain.  The point of maximum chain tension will be when all three points are in a straight line with each other, and some people have used this as the way to work out the optimal chain setting, particularly after making various changes to things.  If you compress the shock until the sprockets are in alignment with the swingarm pivot, the chain will never be tighter than that.  Set it to have a tiny fraction of play at that point, then release the shock to the normal position that you're going to use to remember for adjustment.  A great thing to do at this point is to make a little aluminum jig that you can stick between the chain and swingarm of the proper size, and stick it on your keychain.  Bingo, perfect, repeatable chain tension every time!

The other thing that tears up chains in short order is the power pulses from the engine itself.  The engine doesn't make smooth power, it makes it in a series of burn events (turbines and such exotica excluded).  Big singles, particularly when coupled to wheels lacking cushdrives?  Yeah.  Buy stock in EK or RK.

Impact or zip gun is usually the recommended way to remove a front sprocket, especially with the chain already off or hanging slack, etc.  The big piece of advice that I can give here is make sure the socket absolutely fits and grips as much of the countershaft nut as possible.  For me, this means using a 6 point impact socket that has spent some quality time against a bench grinder.  If you look at most sockets, they have a slight rounding to the edge, the portion that goes onto the nut first (dunno how else to explain it).  I view that as surface area of the nut that it will be unable to grip, so by making the hex shape consistent right to the very end of the socket, you gain a little resistance to rounding the nut, spreading the load over a slightly larger area.  I finally did go back with some sandpaper and a file (use the sandpaper, the file was a waste of time on the hard steel) and broke the edges a bit, after cutting myself on the damned thing.  Works like a champ though.

[movenon]

Face ground down on socket to fit shallow nut.



I just put a 2x4 / a stick ,  crosswise the rear wheel spoke and the swing arm while in high gear.  The TQ on that sprocket should only be around 65 ft ls. Thats out of memory anyhow.

[andyb]

^ Exactly that.  Though I reiterate that I'd use a 6point socket as a starting point.

The other thing to know about gearing bits is that identical ratios can alter the chain tension on the loaded run.  16/48 (to use non-FJ numbers for easier math) will pull less hard on the chain than 15/45.  This changes the tension the chain sees a bit, though as described above, this isn't the big load that the chain worries about.  More importantly, it'll also change the amount of antisquat effect that the swingarm sees, and that'll change how the shock reacts under hard accelleration.  It's not a huge thing to worry about if you're on a streetbike, because a streetbike's suspension is a compromise at the best of times, though it's something to be aware of.  Starts to matter more if you go racing.