Results 1 to 8 of 8

Thread: 20 tooth front sprocket on '16 SR400

  1. #1
    Junior Member
    Join Date
    May 2017
    Location
    Downeast Maine
    Posts
    2

    20 tooth front sprocket on '16 SR400

    Has anybody bumped the front sprocket on a SR400 up to 20 tooth?

    Looking to drop engine RPM at highway speeds to help cut the vibration a little.

  2. #2
    Junior Member
    Join Date
    Mar 2017
    Location
    Sydney, AUS
    Posts
    12
    That's one bigger than standard. Yes i did do it, there was a small change, nothing drastic.
    No mods were required to the casings, even the standard chain still fit.
    For my mind, it mostly made 1st gear better as standard is too short. Highway improvement was negligible.

    Also changed to a 51T on the rear later, now that's nice cruising, beware of big hills though.

  3. #3
    Yes simple change and they're available...

    SR
    ...'Any unnecessary items on the bike, that it doesn't really need, shouldn't be there!'. (Café racers creed). SR..

  4. #4
    I put one during breakup period, bike had around 500 miles on it, gearing felt too short for my taste, been driving it so ever since and don't plan to go back.
    I'm rarely driving over 65 mph, but almost always when have a chance around 60 in 5th, so it fits perfectly to my style.
    To me is important that it drops rpm for 250-300 at given speed, seems not much but makes difference on long runs.

  5. #5
    Senior Member SteveP's Avatar
    Join Date
    Feb 2016
    Location
    Brighton UK
    Posts
    115
    SRMario wrote: it drops rpm for 250-300 at given speed, seems not much but makes difference on long runs

    May not seem much, as you say, but is around 4 or 5 revs per second: A useful reduction.
    If coupled with a 55 rear sprocket as well, this makes for nice cruising, (4,000 revs at 60mph) and you can still get up hills.
    Steve

    Edit: Also got rid of bad vibes in 3rd gear!
    Last edited by SteveP; 06-14-2017 at 03:30 PM. Reason: Additional info

  6. #6
    Quote Originally Posted by SteveP View Post
    SRMario wrote: it drops rpm for 250-300 at given speed, seems not much but makes difference on long runs

    May not seem much, as you say, but is around 4 or 5 revs per second: A useful reduction.
    If coupled with a 55 rear sprocket as well, this makes for nice cruising, (4,000 revs at 60mph) and you can still get up hills.
    Steve

    Edit: Also got rid of bad vibes in 3rd gear!
    That would be even nicer combination Steve.
    If you've tried it, please say how the 4th responds with 20/55,
    is it useful enough for overtaking and what max speed you get in 4th at 6000 rpm?

  7. #7
    Senior Member SteveP's Avatar
    Join Date
    Feb 2016
    Location
    Brighton UK
    Posts
    115
    If PHPaul doesn't mind me replying to SRMario on his thread:

    SRMario wrote: please say how the 4th responds with 20/55,
    is it useful enough for overtaking and what max speed you get in 4th at 6000 rpm?


    It's easy to do 50mph and more in 4th with 20/55. Very good for overtaking.
    I never rev to 6,000rpm!
    Steve

    Edit: Does 40mph at 3000 revs in 4th gear. Equates to 80mph at 6000 revs!!
    Last edited by SteveP; 06-17-2017 at 07:03 AM. Reason: Additional Info

  8. #8
    Quote Originally Posted by SteveP View Post
    If PHPaul doesn't mind me replying to SRMario on his thread:

    SRMario wrote: please say how the 4th responds with 20/55,
    is it useful enough for overtaking and what max speed you get in 4th at 6000 rpm?


    It's easy to do 50mph and more in 4th with 20/55. Very good for overtaking.
    I never rev to 6,000rpm!
    Steve

    Edit: Does 40mph at 3000 revs in 4th gear. Equates to 80mph at 6000 revs!!
    Thanks to Steve's experience,
    last night I also chagned rear sprocket to 55, got nice black one from JT.

    Click image for larger version. 

Name:	DSC_0157.jpg 
Views:	12 
Size:	90.4 KB 
ID:	4082

    For anyone interested,
    quick test on flat road in 5th showed:

    -2500 rpm - 60 km/h
    -3000 - 70
    -3500 - 80
    -4000 - 90
    -4300 - 100
    -4800 - 110
    -5200 - 120.

    100-110 km/h in 5th runs very smooth now,
    with enough power in extended 4th for doing hard work if necessary.
    Last edited by SRMario; 09-07-2017 at 10:19 AM. Reason: invalid attachment

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •