Sprocket question...

[Doc.]

Will it be a good idea to change my sprocket to bump up my speed while knocking down my rpms? It's a '73 CB350.

Reason i'm asking is because riding my bike at 60mph is usually taching at 5800rmps, and that's just not comfortable at all. Bike shakes like hell, feels like it's about to freaking blow up, and just struggles really bad on even somewhat uphills. And the higher i go the worse it gets. As most of you probably already know how that feels.

I wanna be able to use this bike for commute as much as i can, and to commute to work, most of my ride would be on a road that's 55mph speed limit.

That or if there are any other solutions? I'm starting to think about selling the cafe so i could get a faster bike, which i really don't want to

 

[boingk]

Sounds like a very reasonable proposition to me, just do it in baby steps so you don't end up with gearing too tall to be any fun. I'd say go one tooth less on your front sprocket, or about 3 to 4 more on the rear. This should see your revs drop (depending on your current setup) by around about 500 to 1000rpm at a given speed.

You may want to check out this site which I've found useful in the past for calculating gearing. Just input your current primary and final drive ratios (primary will be indicated in manufacturers specs, final is your fornt and rear sprockets) as well as your rear tyre circumfrence and max revs, then tweak setting until you see the rpm/speed combo you want.

Cheers - boingk

 

[Rocan]

Sounds like a very reasonable proposition to me, just do it in baby steps so you don't end up with gearing too tall to be any fun. I'd say go one tooth less on your front sprocket, or about 3 to 4 more on the rear. This should see your revs drop (depending on your current setup) by around about 500 to 1000rpm at a given speed.

You may want to check out this site which I've found useful in the past for calculating gearing. Just input your current primary and final drive ratios (primary will be indicated in manufacturers specs, final is your fornt and rear sprockets) as well as your rear tyre circumfrence and max revs, then tweak setting until you see the rpm/speed combo you want.

Cheers - boingk

other way around. 1 tooth UP on the front to drop the revs, OR 3 teeth DOWN on the rear.

what bike are you running? For some bikes 60MPH on a daily basis is just killer; especially for any amount of time.

P.S.- Dropping the gear ratio down a bit will make the ride a bit more comfortable, but any time you need to overtake or shoot up a hill, your going to need to downshift and slam on the throttle.

P.P.S.- Have you ever considered getting a raggedy bike with a strong engine and more highway oriented for a couple hundred bucks? I mean, i love my bike to death, but anything that has to do with the highway, i dont even really consider. I would just hop on my dads 750 shadow with a nice fat seat and big ol' windshield and enjoy cruising.

 

[DrJ]

I've swapped sprockets. Most extreme I've gone is 18T front and 34T rear but I felt that gearing was too tall. Right now I'm at 17T front with a stock 36T rear and it does reduce RPM at highway speed. Unfortunately the jump from 4th gear to 5th is bigger than between the lower gears, kinda like an overdrive. The taller gearing works great for the first 4 speeds but bogs down when shifting to 5th due to reduced torque and results in a harder to reach top speed. That's why racers use a close ration 5th gear for the 350 to lessen that gap between 4th and 5th. As with many modifications, there are advantages and drawbacks.

 

[CCRider]

Be prepared to buy a new chain too. I installed a 17T front sprocket on my CB450 (up from 15T). Now the chain is too short (by just a fraction of an inch).

CC

 

[boingk]

other way around. 1 tooth UP on the front to drop the revs, OR 3 teeth DOWN on the rear.

Yeah, thats what I meant, thanks for the correction. I've changed my original post to suit.

As for sitting on 60mph, the CB350 should more than be up for it. Honda claimed 36 horses when new and they should be able to hit the ton in stock form. I've got to admit though, after a 200km thrash on my RS125, 5800rpm @ 60mph seems like a dream. Perhaps a bigger bike would solve the problem for you more effectively?

- boingk

 

[Rocan]

Doubt it has enough power to pull +1 front and -3 rear (thats about equivalent of taking 6~7 teeth off rear), you'll be using 3rd~4th more.

thats why we said Or