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Discussion Starter · #1 ·
I need to replace the oil seal behind the front sprocket on my 1969 CB160.
While I'm at it, I'm going to replace the sprockets and chain.

My Stepdad, the original owner of the bike, said that when he was a teenager one of his friends changed out the front sprocket on his 160 to get more "umph" out of the bike.
After riding with a passenger, I'm all for more umph. BUT I don't want to lose any top end. With my daughter on the back
, on flat ground we were cruising along at 65. Downhill, we were doing 70+. Uphill, I had to shift into third to maintain and not lose speed.

*Here's the question*
- Is there a sprocket upgrade for either the front or rear or both that will get me more off the line power and maybe even increase top speed. Or is that combination an impossibility of physics?

Here are the before pics of the sprockets...
 

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Both of those sprockets look to be in pretty good condition.

A sprocket change will not give you more power any more than changing gears on a bicycle will give you more power.

Putting a 3 tooth larger rear sprocket is about the same as a 1 tooth smaller front sprocket. Either of those changes will give you a little more acceleration from a dead start or maybe help you climb that same hill in 4th gear without downshifting. However there is always a trade off. That extra "umph" you feel at lower speeds will cause you to run out of RPM at the upper range and will lower your top speed (assuming you were able to reach red line in top gear with the previous gearing).

You will also be cruising at a higher rpm at the same road speed which may be uncomfortable for the rider/passenger due to more buzzing caused by the higher rpm.

More acceleration and higher top speed can not be achieved with gearing changes alone. It takes engine work to make that happen.
 

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Sensei
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.... You can't get both.... You can change the gearing to get more torque (preceived oomph) OR to ultimately achieve a higher possible top speed (if you don't run out of power getting there)... The engine will produce the same amount of power, it is just how it will be applied to the wheel.... Mike is right, to get both, you need engine work, or a bigger engine.....
 

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Discussion Starter · #4 ·
I kinda knew that from a sprocket change that I was considering for my 2004 CB919. On that bike losing top end doesn't matter to me. I never take it over 100 but it already has enough torque as it is.

What do the AHRMA guys do? I guess they do engine work, duh.

I do like the idea of having more power off the line and not having to downshift going uphill with the rear sprocket change. I apparently have 3 different options available from Honda for the rear sprocket.

I'm trying to not get into the engine, I don't want to race the bike. I just want to be able to keep up with my friends that are taking it easy for me as it is.

Decisions...

Thank you for the replies.


Owen
 

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Are you running out of gear in 5th when you're at top speed? I thought these bikes were power-limited (mine is). In other words, you should be fine to go up a size or two on the rear sprocket and not lose any top speed (you'll just be cruising a higher RPM).

In fact depending on the way it plays out (and thinking about this is isn't likely on our bikes), it would be possible that a bigger sprocket could increase top speed and lower acceleration. Think of this scenario:

Bike runs out of power at around 8000RPM in 5th, setting a top speed of (making these numbers up) 80mph.

Our bikes make max-power at 10,000RPM.

On some bikes (many) top speed is actually achieved in 4th, this may be the case on our bikes (I've honestly never tried). But if the engine won't rev any more in 4th to achieve that 80mph, putting on a bigger sprocket would raise the RPMs in 5th at 80mph, thus allowing the engine to create a bit more power and maybe giving you the ability to go a little faster as you approach redline.

If that makes sense. The only reason a bigger sprocket (which will give you better acceleration off the line) would limit top speed is if your bike is gear limited (or call it engine RPM limited). Modern superbikes are engine rpm limited at top speed (I believe), ours are not (I don't think).
 
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