Changing Sprockets

[vcyclenut]

42 rear, just carrying slightly lower rpm's at speed and higher top speed

Enough for 200mph with 12500rpm red line ?

if you could pull it yes, but I topped out at 192 last run I did, I have a couple tweeks coming to see if I can top that

[cOoTeR]

42 rear, just carrying slightly lower rpm's at speed and higher top speed

Enough for 200mph with 12500rpm red line ?

if you could pull it yes, but I topped out at 192 last run I did, I have a couple tweeks coming to see if I can top that

I hit 191mph on GPS with stock gearing with 12,500 redline. Still had 500rpms to go but the bike was struggling to push through them and I was running out of a safe area to do it.

[Switch18]

42 rear, just carrying slightly lower rpm's at speed and higher top speed

Enough for 200mph with 12500rpm red line ?

if you could pull it yes, but I topped out at 192 last run I did, I have a couple tweeks coming to see if I can top that

Needing to decide soon on what gearing to choose to take me past 200mph. I suspect 19/42 would do it but don't really want to change the front if I can get away with it.

[vcyclenut]

I changed both the first time and it was to much gear, it actually dropped my top speed to 189

[Switch18]

I changed both the first time and it was to much gear, it actually dropped my top speed to 189

That's very interesting. So have you a solution ?

[vcyclenut]

yes just go one up on the front,

[Switch18]

yes just go one up on the front,

Cool. I’ll give that a go buddy.

[Champ87]

A few weeks ago I finally got around to changing the rear sprocket – swapping out the original 44T for a 42T steel sprocket from SupersproxUSA. I’ve put a few hundred miles on the bike with the new gearing and, while it hasn’t made a big difference, it did meet my aim of bringing rpm down to 5,000 at an indicated 85 mph.

When I changed the front sprocket I didn’t feel much difference but, with the combination of +1 front and -2 rear, I could feel the difference the first time I eased out the clutch in first gear. Out on the road it didn’t feel any different running through the gears. Once in top gear it seemed a little more relaxed. At 85 mph it’s only 500 rpm less; not a major change but I’m hoping it’s enough to make long riding days seem less tiring when I eventually get around to doing the sort of trips I did on my Triumph.

Running hard through the gears, I didn’t feel any loss of acceleration. Maybe a stop watch would show some difference but for me the experience was still awesome. Top gear roll-ons didn’t feel quite as responsive but, again, it wasn’t a major difference and may just be me thinking it should be that way rather than any actual change in performance.

My other concern, when I decided to try higher gearing, was how it would feel in traffic. Playing around on an empty back road, I let it run in first gear with zero throttle. Without touching the clutch, the bike settled at an indicated 9 mph and continued that way with no snatching, jerking or any bad behavior. Out of curiosity, I tried the same in top gear - it settled at an indicated 19 mph. Again, there was no misbehavior and it felt like it would run that way all day – although I can’t imagine why anyone would do that. My bike has a vcyclenut flash with idle reduced to 1,050 rpm so that may contribute to the nice low speed manners.

At the other end of the scale, I saw 85 mph in first before grabbing 2nd gear as the tach needle headed towards stock 12,500 rpm red line. The gearing calculator gives a potential top speed of 212 mph at 12,500 rpm but, as vcyclenut mentioned earlier, 19/42 gearing will not help top speed. It seems power available and power needed must coincide around 190 mph and the bike won’t push past that. I don’t think I’ll be losing sleep over that.

For most owners there is really no need to make the changes I made, but for me it’s satisfied a personal preference. As usual, I take pictures and make notes when I’m working on my bike. I’ll write up some notes that may help others when it comes time to change sprockets.

[Switch18]

Great info

[Prof J]

Champ87,

Very comprehensive and detailed instruction set. That'd be a good one for a sticky.

Thanks.