Gear Ratio Tips? Need some insight...

[BigDaddyD]

So for the past year or so I've been running my '77 GS750 around town with a 530 chain conversion and one tooth up on the rear sprocket. Since the motor had about 34-35k on it and I needed to work on it some to get it back in top form, I figured going up a tooth size would help the old girl out a little since I do alot of city driving.

Well, I'm finally to the point where the motor is up and running fairly well, and I'd like to start taking some longer trips out of town which will require freeway riding and +60 speeds.

Now, I'm not so good at figuring out much math, let alone figuring out how the gear ratios work on these bikes, so i was hoping someone here could give me a hand.

Here are some details/specs:
It's a 1977 GS750
Standard size front and rear wheels (I'll get the actual rear tire size tonight)
70mph = 5,000rpm with 1 tooth up on the rear sprocket (current setup)
I weigh approx 230lbs + luggage (and sometimes a girlfriend ;-) when traveling.

I'm looking to get my cruising RPM down to about 4,000 or less @ 70mph HOWEVER, I still need to have adequate power for city driving. In other words, I'd prefer to not have to ride the clutch too much at red-lights.

So what would be a good gear ratio?

 

[rapidray]

Dante, go one tooth bigger on the FRONT sprocket. You should be able to do that with the chain you have. Ray.

 

[kyscootertrash]

Sprockets

Sprockets

Dante, go one tooth bigger on the FRONT sprocket. You should be able to do that with the chain you have. Ray.

+1 going up 1 tooth on front should give the results your looking for.

 

[Steve]

Yes, by going up on the front sprocket you will get closer, but you will not get to 4,000 rpm at 70. Actually, you don't want to do 4,000 rpm at 70 with your 750. You may think you will enjoy a little quieter operation, but in reality, there is not quite enough torque available, so you will have to open the throttle a bit more. This will not only add noise, but add fuel consumption, too. I have not bothered to do the math, but I think adding one tooth to the front sprocket might get you about 4,500 rpm, which should not bee too bad.

.

 

[BigDaddyD]

So do I want to keep it +1 on the front and back or go back to the stock toothed rear and +1 on the front?

 

[80GS750]

i would go plus on on the front, and back to stock or minus 1 on the rear.

if you go plus one on the front and minus one on the rear, you'll be at around 4250 rpms at 70 mph

z1 enterprises has the conversion math on their website, check it out under the maintenance section on the right hand side....

-Nate

 

[80GS750]

when i redid my sprockets and chain, i went with minus 1 on the front, and plus 2 on the rear,

and now i hate it.... zipping around town is awesome cause she pulls hard accelerating, but on the interstate im doing over 5500 at 70. probably closer to 5800 or so.

im gonna go with the +1 up front and -2 on the back, and see if i can get some better highway mileage and keep my rpms down a bit more in town...

i also would like to be around 4k or less at 70.

 

[BigDaddyD]

When running a stock gear set up... where would the rpms normally be around 70mph??

 

[Clone]

I wouldn't want to be turning 4000 at 70(120) as the engine would almost be labouring, my bike is flirting with 4500 at 120k(70mph) and that is about as low as i would want it to go. I think you should look at something in the 4500 range.