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What effect does the sprockets and/or chain size of number of links have on a bike? Does it affect speed or stability or something?
Does it matter about name brand as long as the chain is new?

Going down teeth on the front, or up on the back will improve deceleration at the cost of top speed.

Going up on the front (don't do this) or down on the back will increase top speed and potentially fuel economy, at the cost of acceleration.

Not all chains are the same quality, what chain you should buy depends on the bike.

Sevulturus wrote:Going down teeth on the front, or up on the back will improve deceleration at the cost of top speed.

Sev meant acceleration there I'm sure, not deceleration

Whoops, yeah... Acceleration. Stupid cold meds.

Sevulturus wrote:Going up on the front (don't do this) or down on the back will increase top speed and potentially fuel economy, at the cost of acceleration.

"don't do this" depends on what bike. For the new Triumph Bonnevilles, going up from 17-tooth to 19-tooth on the front sprocket works OK if you're doing a lot of highway riding.

Generally speaking there isn't a lot of clearance in that little sprocket cover. So it's usually a better idea to drop a couple of teeth on the back then to add them to the front.

The larger your sprockets, the longer they last. You will have to consider the clearance available. Larger sprockets require longer chains, and vice versa.

The ratio of the number of teeth on each sprocket determines your final drive ratio, which has an effect on the number of engine rotations per wheel rotation in each gear. The final drive ratio is usually expressed as the number of teeth on the rear wheel sprocket to the number of teeth on the countershaft sprocket. For instance, on my motorcycle, the factory sprockets where 50 teeth on the wheel and 14 teeth on the countershaft. This yields a ratio of 50:14. A ratio can be expressed as a fraction, in this case 50/14. A fraction can be expressed as a decimal, in this case, 3.571. 50:14, 50/14, 3.571:1, and 3.571 all express the same final drive ratio. The countershaft in top gear spins 3.571 rotations for each complete turn of the rear wheel.

Most quality chains these days are o-ring type, which last a long time with a little care. Most non o-ring chains have lightwight construction for better performance under racing conditions. They require more care and do not last as long. There are still a few non o-ring standard weight chains available for people restoring old bikes, but you have to look long and hard. However, standard-weight non o-ring chains are 1/4-to-1/3 the price of o-ring chains, and if you don't mind maintaining them, they can last a long time.

Now, here's the situation with my bike: The factory gearing is very low. From a stop, I'm in third gear before crossing 7 lanes when the light turns green. Over 58mph, the bike starts vibrating enough that hands go numb. The bike easily pulls 65mph, but that speed is uncomfortable because of vibration. The engine provides a very wide a flat torque curve.

Because of the torque characteristics of this engine, I decided to swap out the 14/50 sprocket set for a 15/47 sprocket set. At the same time, I installed a new 0-ring chain to replace the factory non o-ring chain.

The final drive ratio drops from 3.571:1 to 3.133:1. That means the engine speed where vibration becomes uncomfortable will increase by about 13.98% (3.571/3.133=113.98%), so 58mphx113.98%=66mph. This solves my vibration problem since 60mph is the posted speed limit and I usually ride between 60 and 65. The taller gearing also allows me to make it across a big intersection with only one shift instead of two, making low speed traffic much easier to deal with. Note that the gearing change did not change the top speed of the bike, which is still about 75mph.

I needed to adjust the new chain once after about 500 miles. No adjustments necessary the past 1200 miles. I spray the chain with Seafoam to dry it after riding in the rain, then before the first ride the following day I spray it with chain wax to prevent rusting. I suppose when monson season ends I'll need to hit the chain with wax about twice a month. The old chain required adjusting every 200 miles and a daily squirt of chain lube.

Now, my offroad riding is limited to hard dirt and grassy fields, in an area with few real hills, with stock gearing I rode everywhere in 2nd, 3rd or 4th gears. The taller spracket ratio does no harm while offroad, I simply drop to 1st, 2nd, and 3rd.

If I rode in an area with deep sand, big rocks, and steep hills, the new sprockets would hurt. In that situation I would have to give up some top end for more low-speed pull. I would choose sprockets that would allow more engine rpm, and thus more power to the rear wheel, at low speeds. Let's say I choose a 14/60 sprocket set for offroad riding. My new final drive ratio would be 4.286:1, or 83.32% of the original wheel rotation per countershaft rotation. Engine vibration would now become uncomfortable at 48mph, but the bike would not as easily stall on a hill, when crossing deep sand, or when climbing over rocks and logs. With such low gearing, the top speed of the bike would be reduced, but not by the 16.68% indicated. The bike won't pull redline in top gear stock, but probably would with the offroad sprocket set.

Other effects of higher numerical sprocket ratios are more fuel consumption and increased engine wear and noise. These are tradeoffs necessary to pull heavier loads, such as hills, sand, or luggage. Lower numerical sprocket ratios might provide better fuel economy, lower engine speeds, less noise, and, in my case, vibration.

Any gearing change carried to excess can completely destroy a bike's ridability, though. Don't get carried away. For example, I had an XL250 and if memory served, it was fitted with a 14/48 sprocket set, which was great in the flatlands of west Tennessee for riding back roads at 80mph. I spent a summer interning in the mountains of east Kentucky, and worked the clutch hard on the backroads there. First day the shops were open I scrounged up a new chain and 14/72 sprockets. It was a totally different bike climbing hills. The bike redlined at 53mph, useless on the expressways, but that sucker would climb anything.

By the way, if you are going to change sprockets often, for varying riding conditions, it is best to do so in entire sets with the chain. Sprockets and chains wear to each other, and a worn sprocket can wipe out a new chain surprisingly quickly, and vice versa. I see many people replacing a rear wheel sprocket and chain, keeping their stock countershaft sprocket, then wondering why the new chain and sprocket only last half as long as the old ones.

I hope this helps your understanding of your chains and sprockets, and how changing them can affect your enjoyment of your motorcycle.