Well, when i street fightered my bike, gauges went bye-bye for the time being. The day after the guages left, i found a PGI +3 rear sprocket, and combined it with a -1 front. I still have the +2 thrust company, but im running the PGI right now. My question is, does anyone have an f2 with +3/-1 gearing? If so, what kinda rpm do you run at say 60, 80, 100. I was cruisin yesterday on the freeway, first time since the gears, and i felt bad, like i was up in the rpm futher than i should be. Now im pretty sure i was only at like 6, but it felt more. I have stock rear tire size, just curious what rpm im turning at what speeds, top end wise, so in 6th. That would help a ton guys, for a month or so till i get my guages. Thanks again.

By the way, other than the gears, its a stock bike.

 

-1 on front and +3 on the back is a pretty big change. I wouldn't doubt if you were running at least 6k on the highway. My bike had -1 on the front and I was doing 4k at 45mph and I went back to stock and I wnt down 500rpm at that speed. Add the rear sprocket difference and the extra mph andd you will be turning a lot of RPMs.


I'm trying to find my service manual so I can figure out what rpm it would equal. The final drive ratios are listed in the service specs and if I can find the diameter of the tire someone should be able to figure out top speed and rpm in any given gear.

 

yeah, im really thinking about runnin the +2 in the rear. It looks cooler too(anodized red). If anyone is running -1/+2 and they could give me highway specs, that would be awesome. because to get anywhere around here, you have to hit the freeway. Thanks in advance.

 

Here is where I am really stuck.

The stock tire, 160/60/17 is approx 77.12" in circumference. (6.426')
A mile = 5280'
stock gearing is 15/43 or 2.866 final reduction
According to the book, primary reduction is 1.863 (82/44)

1st gear ratio is 2.928 (41/14)
2nd gear ratio is 2.062 (33/16)
3rd gear ratio is 1.588 (27/17)
4th gear ratio is 1.368 (26/19)
5th gear ratio is 1.200 (24/20)
6th gear ratio is 1.086 (25/23)

Where I am stuck is trying to apply the different gear ratios to the formula to figure out how fast the rear wheel is spinning per a given engine rpm. Once I can figure out how fast a wheel is spinning I can figure out travel in mph.

This would be great to know as there are a lot of people who ask what will my top speed be at -1 on the front, or +2 on the rear, or both. (or even at highway speeds) I'm going to try and post this elsewhere for help.

 

OK, figured out the formula with a little help and at 6,000RPM in 6th at the 14 front and 46 rear you would be doing 65.9 mph assuming that the tire is new and the tire height follows the aspect ratio 160/60/17. (24.56 tall)

I worked the numbers based on what I see on my bike in 6th and it should be very close.

Here is an example of the formula I was able to use: (stock gearing)

Example: 2000 rpm engine speed (crankshaft)
Shaft speed out of primary = 2000/1.863= 1074 rpm
shaft speed out of 6th = 1074/1.086= 989 rpm
Wheel speed out of final = 989/2.866 = 345 rpm

Forward speed is the equals the rim speed of the wheel. Using the circumference of 6.426 ft

V=(345 rev/min)*(6.426 ft/rev)*(60 min/hour)*(1 mile/5280 ft)= 25 mph.

Meaning: An engine speed of 2000 rpm should give you a foward speed near 25 mph in 6th gear.

 

well i have -1+3 and when im doing 55 im realy doing 45 it is about 10 mph off from what i did today .... i was riding with my friend and rode along the side of him. he told me his speed and i was 10 mph off from him

 

That doesn't make any sense at all. The speedo sensor is at the front wheel and is independent of what sprockets you have on the bike. Is there more than one sensor on the bike?

 

if you have a different sprocket on your bike the wheels will spin at a different speed with different revs for instance you put big wheels on a car the mph will be diffrent and i have a f3. The mph sensor is in the tranny. no matter what you do to a tranny or gears or no matter where your sensor is the mph will always be different that goes with the milage too. my speedo says 8456k and im really at like 7k and some change there is a big difference there in mph and milage

 

In an F2 the speedo cable is at the front wheel. It doesn't matter what gearing or rear tire size you have, it will read correctly as long as the front tire is stock size and on the pavement. For example, I had a 14t front gear on my bike an did approx 4k at 45 mph. I changed back to the stock 15t and the rps dropped by 500 at that same speed. If the cable was in the trans, the mph and rpms would have read the same regardless of what sprocket sizeI put on there.

I agree that if the speedo cable is in the trans or output shaft than you will change the reading if you change the rear tire size or sprocket size. Guess this is one of the big differences between the F2 and F3

 

yeah the F2 is off the wheel and the F3 is trans read.. i love having it off the front tire.