F800GS 15 Tooth CS Impressions & Questions

Discussion in 'Parallel Universe' started by Desert Dave, Apr 24, 2009.

  1. grndzr0

    grndzr0 its Ground Zero

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    I am Running a 15/43 for the trail, and a 17/43 for the highway. I have done a couple 2 hour highway stints with the 15, wont do them again. Horrible gas mileage, and pretty buzzy. It only takes about 10 minutes if you are slow to change the front sprocket and readjust the chain.

    I have not tried one of the fuel controllers yet, but plan on getting one this summer. So maybe I wont need to be swapping gears out all the time.

    Ryan
  2. JRWooden

    JRWooden Long timer

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    Gary:
    Which are you running?
    I have the IICE cool, but just recently installed it and have not had chance to hit the trails with it yet,
    on the street is seems more "tractable" at low RPM...
  3. Romano

    Romano RR

    Joined:
    Nov 12, 2011
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    5
    Just want to know a good reliable source to put one on my bike.



  4. itsatdm

    itsatdm Long timer

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    I am back to 16. I bought the 15 tooth before the fuel modules and the G2 throttle tube. That will allow you more rpm at the same speed and gets you into a richer part of the rpm band. I did not like it too well because that little snappy throttle was still there and if you found it, it really jerked, because more HP was doing the jerking.

    I ran a 17 for a year with the module and the G2. It smoothed the engine vibes and has enough torque to ride almost any forest service road where I ride.


    But I have a couple of roads in the hood that sound like what the OP is talking about. So I replaced the 17 with stock. Did a ride last week with the 16 tooth. This road has some steep portions with a couple of switch backs. Somebody had done some 'improvements" They dozed the packed dirt and rock with a few sections of loose shale, to get rid of the water erosion . It now had long stretches of fist size broken rock and about 20 water bars, not all where I would prefer them.


    I wish I had taken pics to see if this is what the OP is talking about. I had no problems. I could modulate the power to prevent wheel spin and had enough hp to pull the steep portions. (Grant Ridge DD)

    When you do these mods you really look at the whole bike. IMO they really are not a stand alone solution. Part of the reason it works for me is I have also upgraded the suspension. I can travel over terrain faster than I could stock. The shock of hard impacts is not getting transmitted to my throttle hand.


    In all honesty I have come to the conclusion I am not as good as I used to be:gerg. I see no point in taking a 500lb bike into places I do not feel comfortable riding it there, when I have a perfectly good thumper that easily will do 100miles of pavement. I can't really bad mouth BMW about the gearing when I do the same gear reduction on my KLX 680.
  5. JRWooden

    JRWooden Long timer

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    Thanks! and yeah... I'm pretty much at the same point :lol3
  6. grndzr0

    grndzr0 its Ground Zero

    Joined:
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    http://www.sprocketcenter.com/

    They are the bomb. Very helpful, and great prices!!!


    They helped me pick out the correct ratios, and select a good chain
    at the right length.

    Ryan
  7. daveo987

    daveo987 n00b

    Joined:
    Feb 24, 2012
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    7
    I installed the Power Booster for last "fire road" ride, my impression is : it does seem to help on bottom end, but definately NOT a "fix" , seems to make top end feel "soft", like there was a pwr loss at freeway speeds. Had my friend try my GS ( he also has a GS800) His impressions were about the same as mine.
  8. grndzr0

    grndzr0 its Ground Zero

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    Which one were you using?

    Ryan
  9. itsatdm

    itsatdm Long timer

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    Do you understand all that open loop/closed loop business? It only works when you crack the throttle and put load on the engine. When the oxygen sensor denotes less load on the engine by way of reading exhaust, it starts reverting back to stock mapping.

    I think it feels it is little soft sometimes during hot weather or high altitude, but it always feels better when first cracking the throttle. I really only notice it when shifting. Even then I think the bike accelerates better but the throttle feels a little mushy. Just like a carb'd bike.

    It should not require this, but it seemed to go through a learning cycle. I remember thinking the bike running soft for the first few tanks.

    It is a bandaid. If you want crisp throttle, a power commander can be dialed in for that. But beside the cost you will either lose the oxygen sensor and run in open loop all the time or you will need a wide band oxygen sensor.

    I bought it to deal with the abrupt low rpm throttle caused by the high gearing off road. The rest is a bonus.
  10. Mark5PA

    Mark5PA Long timer

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    Only read this thread back a few pages. Still no joy on a 43 tooth rear? Saw it listed on Sprocket Center, but their site isn't coming up now to check.
  11. ecce

    ecce Been here awhile

    Joined:
    May 20, 2009
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    129
    Location:
    Stockholm, Sweden
    I am running the 15t front and stock back and it works much better off road than the stock 16t front (for my riding style at least). (The only other modification I have made, that matters for riding, is changing to the the pivot pegs which is the best invention since sliced bread :D )

    However... as itsatdm has pointed out the bike will still suffer from low power in the low RPM range and this is my main issue with the bike at the moment.

    So now I wonder which method is best (and cheapest) to solve the issue of the low power/torque at low rpms (below 3k).

    I mainly have the issue on really slow sections where I have to use the first gear and find my self having to run with the clutch slipping all the time, so to say. This is however pretty ok since it doesn't happen that often.

    The other scenario, which is more common, is when riding twisty segments on 2nd gear below 4k rpm. All is fine and dandy until I want to help the bike turn quicker by sliding the rear wheel and there is simply not enough power to do this so I just accelerate. Friends riding the orange 690 don't seem to suffer the same problem.......
  12. grndzr0

    grndzr0 its Ground Zero

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    Location:
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    I just put a 43 on from sprocket center, It is a lot heavier built that the stock sprocket. I am running a 15/43 for the trail, Probably as low as I want to go, It runs pretty hard on the faster gravel sections...

    And 17/43 for the street. This is a tad higher than stock. I like the set up pretty well. I got a longer chain at 118 links when I did the swap. I have plenty of room with this setup to put on an 18T front as well if I wanted.

    Ryan
  13. ebnelson

    ebnelson Frozen rider

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    Nov 16, 2004
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    Boulder
    I was disappointed when my new 15 tooth sprocket, bought from TT, wouldn't fit on the splines of the output shaft. The stock 16 tooth slid right off and back on. I tried a few times, lining it up very precisely and just couldn't get it to drop on. I even tried a couple of light taps with a dead blow and still couldn't get it on. It is the more expensive TT option with the "lightening" holes. Seems like the splines are just to fat on the sprocket. Anyone else have this issue on an aftermarket sprocket? I'm thinking of trying the Renthal one.
  14. itsatdm

    itsatdm Long timer

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    TT makes 2 sprockets. My 15 tooth was the cheap version, it looks like it was as cast. I have the the same problem. The 17 tooth was the high end version and appears to have been bead blasted. It fits as it should.
  15. ebnelson

    ebnelson Frozen rider

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    Did you have any trouble getting a refund out of TT USA? I need to send the offending sprocket back to them in the next few days.
  16. Avner

    Avner Not noob anymore

    Joined:
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    143
    Location:
    Bethesda, MD
    I've been looking at all of the older posts in this thread, and based on that I made my decisions. I'd like to thank everyone for posting such helpful information, so this is my modest contribution:

    Last night I installed the 47-tooth rear sprocket in addition to the GREAT 15-tooth front sprocket upgrade 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 ½" 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" power-line 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!

    Thanks everyone for the advice!

    Avner
  17. Geoffster

    Geoffster Fool - Born This Way

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    My Blue Heaven
    Found this old thread that's been partially resurrected, and wish to comment.

    When I had a G650X, I found that different riders had different gearing preferences. 14, 15, 16, 17 ... (15 was stock on the Challenge, 16 was stock on the Country and Moto.) I found that a 15 on my Country was a good fit.

    Four weeks ago I traded my Country for an F700GS. My first start on a dirt apron told me the stock 17 was all wrong. Yesterday I installed a 16 and am much happier!

    My point is this: EXPERIMENT! Countershaft sprockets are relatively inexpensive and can completely change one's perception of one's bike.

    Fuel mileage? Never saw any difference between a 15 and 16 on my 650.

    Buzzy at freeway speeds? S-l-o-w d-o-w-n. You'll arrive at your next gas stop 10 to 20 minutes later. (A friend with a KLR calls it matching one's expectations to one's bike.)
  18. Calgary06

    Calgary06 Been here awhile

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  19. JRWooden

    JRWooden Long timer

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    For $3 I think I will be a sport and replace the spring washer when I do mine, but think I'll leave the seal alone ... I'd like to think its going to last ... and it might be a pain in the a$$ to replace?
  20. RexBuck

    RexBuck Long timer

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    No. I've changed my sprocket back and forth a couple of times and have not changed any other parts. That doesn't mean you shouldn't (I'm a mechanical idiot and don't know what is correct), just that so far my bike has not fallen apart as a result.