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Old 04-24-2013, 11:42 AM   #16
Metalsapo OP
R.E. Ordoez
Joined: Feb 2013
Location: Guatemala C.A.
Oddometer: 41

Yesterday i got my answers, i went to the BMW and asked to the mechanic manager (i hope you understand this) what i could get from a sprocket change, if it is good or not?
He said that is a very common modification (back or front)for 800 parallel twins, and it is done in the process of competition to get more control and torque response to the off road technical conditions, and when the motorcycle is on the pavement and the upper gears (6th' 5th) are used is when the gasoline use is not efficient.
With that said, i made my choice, and i choose to practice more.
Im a new rider, scince November 2012, just 4500 km of experience and about 1300 km off road until today, so i am very rookie and the practice i have is just in the ride to work and a couple of other small trips like the picture is showing, i do 12km or a little more off road and the rest is bad pavement and the city cahos every 3 or 2 days, also the offroad course i assisted was limited in this area of downhill so i do more than i learned there, i have crashed once after the course and twice before, your advice is correct and i must place my body correctly to help traction, braking, and balancing the bike, i am very honest about it, and it is very scary for me sometimes when terrain is too dry and loose in downhill sections, i think is normal to feel fear, and fear is telling me like a good friend to be carefull, fear inside of me must be trained to back off a little bit to let me do what im learning to do, so if i do feel that i could modify the sprocket (available from touratech or original BMW) in the future i will, but meanwhile i will do my practice.
Thank you all. (Sorry for spelling, ipad is not that easy for this)
F650GS 08 Red
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Old 04-25-2013, 12:50 PM   #17
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itsatdm's Avatar
Joined: Jun 2004
Location: Nor Ca.
Oddometer: 5,000
It is a fairly common mod. The mechanic is correct if you mean it will raise the bikes rpm vs speed on pavement. On a F800gs, 128 kph is about 5,000 rpm. I would guess on yours, with its gearing it would be around 4,700 rpm. Am I close?

You have to keep in mind that the transmission is supplying its own multiplication of the gearing. In other words a 6% gear reduction overall, is more in the lower gears than the top gears.

It is also simple to do. Take the cover off the sprocket. 1 bolt holds the sprocket on. The same chain works with either, you just have to adjust it.

Counting stock I have 3 sizes. I detect little difference in mileage with the various sprockets.
BMW Motorrad USA customer service: "We make superior motorcycles and continue to improve them."
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Old 04-25-2013, 08:30 PM   #18
Not noob anymore
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Joined: Aug 2011
Location: Bethesda, MD
Oddometer: 137
Say YES to Sprocket Change

I posted it on another thread, but you can read the short version:

Switching the front sprocket from the stock 16 to 15 tooth is something anyone who ever leaves the pavement should do, because in my opinion the stock should be the 15-tooth sprocket; it does much better on and off-road. It will only cost $32 or less and takes less than 15 minutes to replace. However, it is just an improvement and not a game-changer, and you will still have to slip the clutch a lot in technical terrain.

If you really want to have good control and high torque off-road, then replacing the rear stock 42-tooth sprocket with a 47-tooth one is the way to go:

Last night I installed the 47-tooth rear sprocket in addition to the GREAT 15-tooth front sprocket mod from last week, so now I’m running 15/47.

The chain was too short after adding the 47-tooth sprocket, but I didn't feel like spending $145 on a new chain because all I needed was " more. The only thing limiting the rear wheel from moving forward was the chain-tension screw. I fastened it all the way in, but it was too long and it was sticking out and not being able to go all the way in. Since I’ll never need the full length of the screw (my 15-tooth front is permanent because it has the best balance for road/off-road), I just cut it off and everything now fits perfectly. I even had to give it a few turns, because the chain was too loose with the screw all the way in.

Two major improvements I felt right away when I visited my "private" off-road area last night:

1- The bike can crawl on 1rst gear with no throttle added. It was very useful when I was going down a steep hill without touching the clutch or the brakes, and it is harder to stall the bike even in low RPM.
2- I know I’m only gaining about 10% of torque with this setup, but when I tried climbing up a familiar steep hill I felt as if I got 50% more torque – it was almost effortless!

The down-side is obviously more buzz because the RPM is now “living” in the 5,000 range (which I like doing anyway), and long highway hauls would be tiring with an estimated 6,000 RPM at 80MPH. I never checked my MPG, so I won’t be able to compare, but I’m sure it will be affected as well. However, I’m very happy because my main concern is the low-end anyway, and this $122 modification completely transformed this bike into a mud-craving bitch!
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Old 04-26-2013, 10:28 AM   #19
Metalsapo OP
R.E. Ordoez
Joined: Feb 2013
Location: Guatemala C.A.
Oddometer: 41
I never checked my MPG, so I wont be able to compare, but Im sure it will be affected as well. However, Im very happy because my main concern is the low-end anyway, and this $122 modification completely transformed this bike into a mud-craving bitch!
Abner, thank you, i will purchase the sprocket very soon and re thread you with my modification results, i take notes of the KPG i do with the bike, and average is doing 90 KPG, and the modification will be for the back sprocket using a 42, and i feel better to have your same problem and that the solution is easy, my sporcket will be from touratech for $84, so i let you know.
F650GS 08 Red
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