I've come up with a fairly simply and easy to do modification that results in significantly smoother gear shifting, ideal for anyone who isn't quite happy with how their shifting behaves, which I've been testing and modifiying over the last few weeks to come up with an optimal solution.
I understand that the majority of people have no issues with the shifting of their 650's, but my (bought used) 2018 CBR650F was the worst behaving bike I've had to date in over 10 years of riding and 30+ bikes owned. My symptoms were occasional, and somewhat random notchy shifts between 1st and 2nd as well as 2nd and 3rd, which would cause the gearbox to occasionaly get stuck passing through neutral often requiring a second kick to get up into 2nd or back down to 1st. The 1st up to 2nd was the most problematic and caught me out several times taking off from the lights leaving me stuck in neutral when I'd thought I'd kicked it up into 2nd. After attempting:
- Clutch lever freeplay adjustment.
- Shifter linkage adjustment.
- Setting chain slack to the tighter end.
- Cleaning and regreasing the lower shifter pivot at the frame.
- Installing a shift support.
I still wasn't happy. Overall shifting improved between all gears, but I'd still get random stiff shifts between 1st and 2nd (both directions) and 2nd to 3rd (upshift) which made city commuting a pain in the butt.
I had an idea, which was to trial a shorter shift arm from the shifter spline which would in effect reduce the travel of the shift lever required to change gears. The thought behind this was that if the lever had to move less distance to change gears, then there might be less chance of it hanging up in neutral on the way through. I also expected that this could make things worse as the reduction in movement would result in an increase in effort required to shift (mathematics / engineering in play). This test was a brutal failure. The shorter shift arm, whilst reducing the shifting distance, made shifting significantly stiffer and worsened any occurances of notchiness and bad shifts. Knowing how much impact this had, I moved on to a second trial, which was a longer shift arm.
Stock shift arm = 45mm from shifter spline to linkage centre.
Shorter shift arm (trial 1) = 30mm from shifter spline to linkage centre. Far worse shifting.
Longer shift arm (trial 2) = 60mm from shifter spline to linkage centre. Significantly smoother shifting across the board and almost no occurances of notchy or missed shifts. More of an extreme adjustment to try and find the ideal limit. Shifter movement was perhaps slightly longer than ideal with the linkage offset this far from the spline.
Longer shift arm (trial 3) = 50mm. Using a cut-down aluminium gear shifter ($9AUD delivered on Aliexpress) for rigidity and a more "OEM" look. These levers angle outwards slightly, so it was a bit trickier to get the ball joint to sit at the exact distance I wanted it. Aiming for 55mm, I misjudged the angle I drilled where drilling through at about 44mm landed me on a 50mm offset linkage from the spline. This felt worse than the 60mm option, though slightly better than standard.
Longer shift arm (trial 4) = 55mm. Using another cut down aluminium gear shifter I got right on 55mm which was my target. This is the best position, which gives significantly smoother shifting across the board and pretty much eliminates any notchiness between 1st, 2nd, 3rd. The extra throw of the shifter is not noticable because pushing the shifter requires a fair bit less effort than standard. Per the second picture, this required drilling a hole about 46mm from the edge of the spline which ends up positioning the ball joint at a 55mm centre from the spline (first pic).
This is the lever I bought which I cut down and used to make the shift arm, though you could use anything with a 10mm clamp for the spline.
I also used a generic Left Hand Thread ball joint and an M6 tap to thread a hole through my new lever. You could also just drill to 6mm and use regular nut and bolt, but I liked the idea of tapping the 6mm thread to make everything more solid and secure.
In summary, if you're not entirely happy with your shifting after making all of the common adjustments then I'd highly recommend giving this a go. All you need is the parts above, a shallow cap ended M6 bolt (needs to be shallow to clear the chain guard unless you mount the ball joint on the outside), a hacksaw/grinder and a 6mm drill bit (or 5mm drill bit and M6 tap). Note that in my finished picture above, I have the ball joint mounted behind the shift arm which pretty much has it sitting directly vertical from the pivot on the lever itself. In theory this would also assist with shifting compared to stock, which has the upper ball joint sitting a fair bit further out from the bike. This has completely solved my only gripe with the bike and now I can concentrate of enjoying the ride rather than concentrating so much on getting a proper shift when slipping through the gears in low speed traffic.
I understand that the majority of people have no issues with the shifting of their 650's, but my (bought used) 2018 CBR650F was the worst behaving bike I've had to date in over 10 years of riding and 30+ bikes owned. My symptoms were occasional, and somewhat random notchy shifts between 1st and 2nd as well as 2nd and 3rd, which would cause the gearbox to occasionaly get stuck passing through neutral often requiring a second kick to get up into 2nd or back down to 1st. The 1st up to 2nd was the most problematic and caught me out several times taking off from the lights leaving me stuck in neutral when I'd thought I'd kicked it up into 2nd. After attempting:
- Clutch lever freeplay adjustment.
- Shifter linkage adjustment.
- Setting chain slack to the tighter end.
- Cleaning and regreasing the lower shifter pivot at the frame.
- Installing a shift support.
I still wasn't happy. Overall shifting improved between all gears, but I'd still get random stiff shifts between 1st and 2nd (both directions) and 2nd to 3rd (upshift) which made city commuting a pain in the butt.
I had an idea, which was to trial a shorter shift arm from the shifter spline which would in effect reduce the travel of the shift lever required to change gears. The thought behind this was that if the lever had to move less distance to change gears, then there might be less chance of it hanging up in neutral on the way through. I also expected that this could make things worse as the reduction in movement would result in an increase in effort required to shift (mathematics / engineering in play). This test was a brutal failure. The shorter shift arm, whilst reducing the shifting distance, made shifting significantly stiffer and worsened any occurances of notchiness and bad shifts. Knowing how much impact this had, I moved on to a second trial, which was a longer shift arm.
Stock shift arm = 45mm from shifter spline to linkage centre.
Shorter shift arm (trial 1) = 30mm from shifter spline to linkage centre. Far worse shifting.
Longer shift arm (trial 2) = 60mm from shifter spline to linkage centre. Significantly smoother shifting across the board and almost no occurances of notchy or missed shifts. More of an extreme adjustment to try and find the ideal limit. Shifter movement was perhaps slightly longer than ideal with the linkage offset this far from the spline.
Longer shift arm (trial 3) = 50mm. Using a cut-down aluminium gear shifter ($9AUD delivered on Aliexpress) for rigidity and a more "OEM" look. These levers angle outwards slightly, so it was a bit trickier to get the ball joint to sit at the exact distance I wanted it. Aiming for 55mm, I misjudged the angle I drilled where drilling through at about 44mm landed me on a 50mm offset linkage from the spline. This felt worse than the 60mm option, though slightly better than standard.
Longer shift arm (trial 4) = 55mm. Using another cut down aluminium gear shifter I got right on 55mm which was my target. This is the best position, which gives significantly smoother shifting across the board and pretty much eliminates any notchiness between 1st, 2nd, 3rd. The extra throw of the shifter is not noticable because pushing the shifter requires a fair bit less effort than standard. Per the second picture, this required drilling a hole about 46mm from the edge of the spline which ends up positioning the ball joint at a 55mm centre from the spline (first pic).
This is the lever I bought which I cut down and used to make the shift arm, though you could use anything with a 10mm clamp for the spline.
I also used a generic Left Hand Thread ball joint and an M6 tap to thread a hole through my new lever. You could also just drill to 6mm and use regular nut and bolt, but I liked the idea of tapping the 6mm thread to make everything more solid and secure.
In summary, if you're not entirely happy with your shifting after making all of the common adjustments then I'd highly recommend giving this a go. All you need is the parts above, a shallow cap ended M6 bolt (needs to be shallow to clear the chain guard unless you mount the ball joint on the outside), a hacksaw/grinder and a 6mm drill bit (or 5mm drill bit and M6 tap). Note that in my finished picture above, I have the ball joint mounted behind the shift arm which pretty much has it sitting directly vertical from the pivot on the lever itself. In theory this would also assist with shifting compared to stock, which has the upper ball joint sitting a fair bit further out from the bike. This has completely solved my only gripe with the bike and now I can concentrate of enjoying the ride rather than concentrating so much on getting a proper shift when slipping through the gears in low speed traffic.
