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[Rattlebattle]

Is it perhaps that the rear sprocket is a different size? it has presumably been redesigned to accommodate the disc brake. If it is different then a one tooth increase would be good; if not I'd go up two teeth.

[Alan R]

Hi guys---- just to confirm that wee bit 'o maths earlier}----- on a 17 tooth sprocket, 1 tooth divided by 17 = 0.05882 or just under a 6% change in the overall ratio...whilst a 2-tooth change (ie 17 to 19) is 2 divided by 17 = 0.11764 or just under 11.75% change...in relation to the original 17t sprocket..

If you are already on an 18t sprocket then a one tooth increase is shown thus}--- 1 divided by 18 = 0.05555 or just on a 5.5% change...

[Revband]

You are correct, just under 6% (5.71429 actually) for 17 to 18, maths and alcohol don't mix. But 6% under 3mph at 50, not worth the expense and effort surely?.

[Leon Novello]

A simple and easy way to check if the gearing is correct, is to find a long flat road and see if the engine can achieve peak power revs in top gear. This is more noticeable when a sidecar is fitted and the rider finds the engine can`t rev high enough in top gear, so what is called `sidecar gearing` needs to be done.

[oldnick]

Thanks for all your comments. I have just counted teeth on rear sprocket - it's still 38. So both the B5 and C5 EuroIV (2017 on) seem to have lower gearing than previous models. The B5 still with 17 teeth GB sprocket but now with 18" wheels and the C5 now with 17 teeth GB sprocket and still with 18" wheel. I wonder why - is there a reason or just another RE oddity? Still undecided about whether to go with 18 or 19 teeth GB sprocket.

[Rattlebattle]

Whilst the change from an 18 to a 19 tooth gearbox sprocket mathematically isn’t that high, in my experience it does make a noticeable difference on the road. It takes a little away from acceleration (and let’s face it they only gather speed really in relative terms) but it also makes constant speed cruising noticeably more relaxed. If one only cruises at 50mph indicated then don’t bother. But at an indicated 70mph the engine on mine is smoother than it was. Also, first gear seems more useable and the acceleration loss can easily be compensated for by using the gearbox more. I wouldn’t go back to standard gearing and if the Euro IV really does have a smaller sprocket but remains the same otherwise then IMHO it must be undergeared and quite nasty if the engine is on the vibratory end of the spectrum. They do vary according to how accurately the crank is balanced.

[Jack the Lad]

I went up a tooth on my Electra efi when the sprockets needed changing anyway. Wish I had done it sooner. It didn't make any difference to top speed and cruising at 60-65 was always OK, but the difference to the intermediate gears was significant. Instead of being just too short for village speed limits, roundabouts and junctions, the gearing was just right. A few extra mph in fourth made passing trucks just that bit safer.

[Rattlebattle]

My findings exactly. On standard gearing I always found that at 30mph and 40mph limits the engine was revving just a little too much. I now find that it’s perfect using 3rd in 30 limits and 4th in 40 limits. I usually put it in top at 50 mph now; much better. I doubt top speed is affected much because it lacks the oomph to take advantage of the taller gearing but it is better changing down to fourth for a cleaner, more decisive overtake.

[Rusky]

For any of you who have followed my story so far I have now completed the installation of a stage 1 Performance upgrade kit to my 2005 500 Electra X.Now I know that this thread is considering the merits of changing up front sprocket on a 2017 EFI and my old brute is a dinosaur by comparison but my findings may be of interest.
I have been happy with my bike for a long time now, and it’s a great improvement over the 350 I own of a similar age. Many out there who own a 350 claim the engine to be “sweeter” or better in some way. As owner of both I can tell you that view is simply wrong. Sorry to be controversial but put simply it’s a piston moving up, an explosion and a flywheel turning, it’s not rocket science and despite the “opinions” of several the actual size of the swept volume has little to do with “sweetness” If you want more power, burn more fossil fuel. End of.

Back to the project report. It was late last year when frankly feeling a bit stressed at 58mph trying to keep up with my mates on their Norton’s and Triumphs that I realised something must be done. I do have faster bikes, a lovely 650 Bonneville and a Ducati that pulls my arm sockets out if you open the throttle at 100mph. So what was to be done, it’s the Enfield I ride most and certainly when the English summer is doing its best to spoil my fun. I simply needed a little more speed, not much just a slight increase would be fine but, and this is important, I needed to feel I wasn’t wringing the neck out of the old girl at 60mph.(I do mean a true 60mph as I use my iPhone as a speedo)

Much debate was had on my local forum about my decision to change the gearbox sprocket from an 18 tooth to a 20 tooth, an 11% increase in gearing.
Many suggested that this would be way too much and some even produced calculations to prove it. Thanks to all who contributed, I appreciate it and here at least I wouldn’t say anyone is wrong, success after all can only ever be an opinion.

A new 32mm Amal carb, free flowing front exhaust, removal of the PAV, a new and longer reynolds chain together with a few cables and TLC and the old girl was ready for a test run. Our hosts suggest these changes to my 2005 Electra up the power by 40%.

I admit it, I have only done a couple of hundred miles since the changes but what a revalation. I can say with certainty that the gamble has paid off. The nay sayers who said it wouldn’t pull top were mistaken, at 60mph into a strong headwind open the throttle and WOW, it accelerates to 70 remarkably quickly. A long effortless run on a dual carriageway at 70mph confirms I now have a really good long distance tourer, quite honestly it’s so relaxed, I checked to make sure I hadn’t taken my Ducati by mistake (okay I’m exaggerating, but you get the picture)
The high gearing makes the lower gears worth having. So many times I used to wonder what 3rd and 4th were really for, after all you could plod in 5th at 30mph so why all those gears? I still can, at 30mph in 5th okay, truthfully 4th was much better, but then again 4th now is my old 5th gear.
Tick over is smooth and all works fine.

I won’t summarise here, its far too early to do that. I plan to take some detailed measurements of performance over the next few weeks. I will video my speedo and iPhone so we can all see the outcome, you can then make your own minds up.I will try and find a private road and see what she will do flat out together with some 0-60 times etc.

Please don’t be offended by anything I’ve said, simply opinion, but it does suggest that a 20 tooth front sprocket on a bike that our hosts suggest will now have a 40% increase in BHP at the rear wheel is viable.


Until I ride and report again, your views are all most welcome.

[Revband]

Some interesting and sensible comments there, but, take the 40% increase advised with a large pinch of salt, I have spent many years tuning this style of engine and 40% is achievable but not that easily I am afraid.