changing gear ratio

[jason-1995fbody]

ok i have a 73 honda cb 350 yeah its small and old but i got it for 100 bucks running and gas is like 3.19 a gallon so i ride as much as posible and get about 40 to 50 mpg but i run the highway alot and the bike runs 6000 to 7000 rpm sorry i ramble anyway i want to change the gear ratio so its not screamin at speed so do i need a moree or less tooth sprocket in the rear and do you know how many teeth are on my factory sprocket thanks in advance

[jeffcoslacker]

I think the gears are like 14/32 on that bike, I had one, that seems close. That would give you 2.29:1 ratio. Lowering the first number gives you lower revs and less torque. A 15/32 combo would give you 2.13:1, 16/32 would put you at 2.00:1.

So from a 2.29 to a 2.13 would be about a 7.5% change, so you'd see a similar reduction in engine rpm, say if you are turning 6500 rpm to go 70 mph now, this would put you at a little over 6000 rpm. Not really a big change in sound or anything, will improve mileage a bit, but low end performance will SUCK....which is why I don't really recommend it...that bike will run 8000 rpm all day long and never complain (I used to have one just like it)...just learn to enjoy the sound is my advice. Put some glasspacks on it. That's what I did. Sounded like a sportbike

[jeffcoslacker]

PS to lower rpm, you'd need to increase FRONT sprocket size...they probably only have larger (more teeth) rears, which will only increase rpm...

[jason-1995fbody]

so larger front gear and smaller front gear or som combination like that ok thanks

ive got open pipes now and im not to concerned about performance just tryin to savea little money and yeah at6 grand thows pipes are insanely loud

[jeffcoslacker]

You probably don't need to do anything with the rear...as long as the upsize on the front yeilds what you want. Then if it's a bit too much, you can change rear up by a tooth or two to fine tune the ratio...

[richtazz]

larger front sprocket + smaller rear sprocket = lower highway RPM. Just be careful not to go too far or it will barely get out of it's own way from a dead stop.

[aussieidiot]

it doesn't matter which one you change (front or back)

one tooth up on the front is the same as going about 3 down on the rear.

for mine i wanted more acceleration so i went 1 down on my front. from 16/40 to a 15/40. heaps of difference. then i went 2 up on the rear to a 42.

just be careful on the front. the sprocket cover may interfere with a 2 up conversion

i know i can't go any lower or the chain will eat through my swing arm

[jason-1995fbody]

thanks guys lots of good info