TOPIC:

I found an Excel sheet that calculates gear ratios, speeds, etc. The filebase would not accept an upload for an .xls file. I guess this is not allowed due to possible embedded viruses?

I'll provide a link to the website here, and everyone can download it from there.

Motorcycle Gearing Worksheet

Enter gear ratios, tire size, sprocket sizes, in the pink column, it will calculate from there. By changing the "Engine Maximum RPM" you can figure out top speeds, cruising speeds, etc.

Be aware that the top blue rows are in KPH, and the bottom blue rows are miles per hour.

Haha, just so I know I'm doing this right.

What should my sheet look like for a 650 Kent?

What are the stock sprocket teeth on the 650?

Edit: and on that subject, how do I know what my primary drive ratio is...?

Post edited by: nfswift, at: 2006/02/15 23:35

got a shop manual?

nfswift wrote:

Edit: and on that subject, how do I know what my primary drive ratio is...?

It's not too hard to figure out. I didn't see it listed anywhere (or even the number of teeth on the crank or secondary shaft).

Open the oil filler cap and mark the clutch with a marker or scratch it. Then rotate the crank full rotations until the clutch makes an exact number of turns. Take the plugs out so you don't have to fight compression.

On my 550, 46 clutch rotations takes exactly 135 crank rotations. No other number of crank rotations would give me an exact number of clutch rotations.

That's your primary ratio (crank to clutch). The clutch is the transmission's input shaft. The chain sprocket is on the transmission's output shaft, and you know your trans ratios. The rest is chain and sprocket. I actually measured the distance for 10 tire rotations to get it exact.

Will this program tell you what size sprockets to run for a certain application. I need to know for my CB project. It will have a larger rear tire so I need to know what size rear and front sprockets to run. Thanks

Yes kawtoy, enter your rear wheel info, and play around with different sprocket sizes. That's what got me looking in the first place, when Tower_Monkey said he was going with a 17/41 combination. I thought, " What would that give him?"

Heres the 650 info

Values (Enter)
Primary Drive Ratio 2.550
1st Gear Ratio 2.330
2nd Gear Ratio 1.630
3rd Gear Ratio 1.270
4th Gear Ratio 1.040
5th Gear Ratio 0.890
6th Gear Ratio * N/A
Front Sprocket (Teeth) 16
Rear Sprocket (Teeth) 42
Wheel Rim Size (Inches) 18
Tyre Width (MM) 120
Tyre Depth (%) 80
Engine Minimum RPM 2,500
Engine Maximum RPM 9,000
Change Down RPM 3,000
Change Up RPM 7,000
Maximum Power RPM 7,500

I found it to be VERY accurate.
At 4500 rpm in 5th I am going at 58mph indicated. So it stands to reason at 9000 redline I could hit 116, or a wall when the power runs out..

It is just a coincidence my speedo happens to say 58mph at 4500rpm, what is the chance of two different instruments that we know are not 100% accurate(especially the speedo) matching this spreadsheet???

Post edited by: OKC_Kent, at: 2006/02/16 15:04

OKC_Kent wrote:

So it stands to reason at 9000 redline I could hit 116
Post edited by: OKC_Kent, at: 2006/02/16 15:04

that sounds about right. the fastest i've taken my 650 was 115, and it was just at the 9000 redline. it was sure whining loudly then...

-bt

Post edited by: bionicTechnophobe, at: 2006/02/17 11:11