Hitchcocks Forum

My 2016 B5 cruises at 50-55 vibe free but I would like to up the speed to 55-60. Please can someone who understands all this gearing and ratios gobbledegook very kindly work out the increase in speed/drop in revs for a + 1 tooth (18) or +2 tooth (19) g'box sprocket and tell me which one to get from our hosts?

Nigel, I've got a spreadsheet which you can put the various figures into and it gives you the speed in each gear etc. If you email me at mark dot bailey at holtbyturner dot co dot uk I can send it to you.

Cheers, Mark.

Most people go up 1 tooth on the gearbox sprocket; filing is required to accommodate the largest sprocket, which may be a bit too big depending on the weight of the rider, state of tune etc. Maybe also RE don't consider a two teeth bigger sprocket a realistic option? I suppose I just want to make the point that the precise increase in overall gearing is only one aspect to consider; the result will not in practice be linear, there will be a trade-off with tractability and it might not pull the theoretical top speed. Plenty on this forum and others have done this mod.

Your B5 should cruise vibe-free at 65-ish but being a 2016 it may not be fully run in yet. That can take 600-1200 miles, or more. If you put the C5's 18T cog on, or even the 19T, then you would increase the potential top speed. But it would reduce power by using lower revs; Catch 22. If you up the gearing you reduce the revs needed for 60mph but you reduce the power so it may not pull as well. Acceleration or top speed? - it's a trade off. Personally I prefer more low down torque, I seldom feel the need to go flat out and lie on the tank.

I have lightly tuned my C5 with exhaust, K&N and PCV, but it can and will cruise at 70+mph without feeling like a food blender. It is on standard gearing with 2200+miles on the clock.



Imo better to cure the vibration. - Complete its running-in fully. This is very important to reduce vibes. - Ensure the head stay is nice and tight. - Loosen the front engine mounts, run the motor (don't ride it), then re-tighten. (I have not needed to do this but it re-seats the engine). If the exhaust to head clamp is loose you will not only hear it but your eyeballs will pop out, and that is a point - the entire exhaust system needs to be hung on the frame in a neutral position not stretched and forced to fit, or that will transmit a lot of vibration.

You can change the silencer on the stock ECU which will give a small boost of power and may feel smoother. If you change the entire exhaust system and add the K&N it confuses the ECU and then you need the PCV to fix the mix. Not cheap and something to be done only when it is run in.



Most of the vibration comes up the front tube of the frame and the engine is a stressed member of the frame. The bike is noted for loosening nuts and bolts when new so re-tighten everything and use Loctite.



I have also spread-sheeted the gears with stock gears and stock tyres - both the B5 and C5 are 17mph/1000rpm in 5th gear. This gives a top speed of 83mph at 5000rpm. The rev-limiter is 5500rpm (91mph) but I very much doubt it will produce enough power to pull much over 5100rpm (85mph) in top due to wind resistance (increases with the square of velocity).

There are some discrepancies on sources giving the outer diameter of the RoadRider and SkidMaster tyres, I used Avon's numbers



This one https://www.youtube.com/watch?v=Nn7uwaG7kPs at about 5:00 has my C5 going uphill to about 70mph but it's not at full chat because the road is far from flat, it bucks and kicks all over the place, besides which it leads into a blind junction on an s-bend. Watch the tacho

Rattlebattle et al - H say the 19T will fit without the angle-grinder but that the 20T does require modifying the case. I've hummed and ha-ed on this one and decided no because I can go fast enough comfortably. But as and when I change the C5 rear tyre it will be the next size up, 120/80-18 from 110/80-18, which is "half a cog". And you can put a bigger cover on the Bullet rim too.

Jeff, thanks for the very detailed response. I have done 1300 miles and don't have any problems with vibration. The bike was delivered to me not having been PDI'd whatsoever (see thread 'Tossers' on here) and one of the first jobs was to tighten the engine mounts (a couple were at 15 lbs feet and under the engine was finger tight!). Having screwed the engine into the frame properly all vibration was cured instantly. I have also replaced the exhaust with Mr.H's very nice sounding 91080 and as that has only one mounting bracket there is no chance of vibes from there. Its not vibes that are the problem, I just like a nice lazy thump thump thump but at 60-65 the engine on the B5 (lower geared than the C5) is working just a tad too high up the rev range. Like you I'm not too interested in exploring Warp factor 2 and am happy with whatever top speed I get. Rattlebattle's suggestion that 2t would mean filing the rh case does make me feel an 18 would be best.

From reading the various posts on this and other forums it seems that those who change the gearing usually go up just one tooth. The standard gearbox sprockets on the B5 and C5 differ by one tooth but this is offset by the different tyre sizes. I intend to raise the gearing by one tooth on my C5 but I'll wait until either the cover has to be removed for some other purpose, hopefully just the service that requires it, or the chain and/or sprockets wear out. I think that I'd be better trying to cure the vibes first. Oddly enough mine smoothed out as the mileage increased, as expected, but then the vibes worsened. I can't relate this to anything I've done to the bike, so maybe a thorough going over of all mounting bolts will help. I'll do this at the next service in about 200 miles. Here's hoping....

This reply will be of little help, but...


It is a pity that the 350 isn't available in the UK, it is a LOT smoother, and has similar performance to the older 500.


What with it having a carb (same item as the old Electra X) it responds to basic tuning with little drama or expense. It is proving to be a popular bike in Australia and New Zealand.

Also note, higher gearing means more gear changes.

Leon, not necessarily. Most of the routes I travel are mid-shires A and B roads with relatively little traffic so once I'm in top I can chug along and m-y-o-b without going up and down the 'box like a UJM. Thanks for all replies good people, I'm going with a +1t to 18 as I'm only seeking to drop the revs by 300 or so at 55-60mph.