Forum

[jefrs]

Papasmurf, you're right, poor choice of words, it's expensive but not a complete rebuild of the wheel, only the brake.- The original sprocket is part of the brake drum, which fits by cush-drive into the rear hub. One needs to purchase the machined drum plus the bolt-on sprocket kit - about £110. But we are still limited to minimum 38T sprocket, so I fail to see the benefit.

[PeteF]

Jefrs,
"you have to change the rear hub"
No you don't>
"Fairly simple cover off, change cog"
Hardly; outer cover off, clutch, alternator and primary drive off, inner case off; then you can change the sprocket (and reassemble everything)
"a higher ratio reduces the effort the motor can provide to the wheel"
No it doesn't. It just alters where the "rev band" is. This might take a few mph off top speed but if you run an Electra X at top speed it won't last long.

[Graham43]

sorry sorry sorry it was late when I asked this question. Of course having a larger rear sprocket would lower the gearing! So looks like a bit of a strip down unless someone makes a larger engine sprocket?

[Adrian]

Our hosts list them from 26 to 29 teeth (25 is standard), but for kickstart models only. No use if you were planning on keeping the electric start. A.

[jefrs]

PeteF, yes I should not have said "you have to change the rear hub" when I think I was trying to type something like, "you have to change out the brake in the hub" - one of the limitations of not being able to tpye or edit, brain goinf faster than fingers and found a false neutral. Sorry about that.



I consider taking engine covers off about as simple as doing an oil change. Changing the gearbox cog can provide a higher ratio and is less expensive than the rear sprocket option. There again the Electra(X) box is more complicated to get at that the EFI job I've looked into.



However you then say, "It just alters where the "rev band" is. This might take a few mph off top speed but if you run an Electra X at top speed it won't last long."

Why do you think its top speed is lower?

I used the word 'effort' on purpose. We have to look at the power band and gearing. We use gears to deliver the power to the rear wheel The motor still has the same power but by using a higher ratio can no longer deliver the same motive effort to attain ultimate top speed. The final drive becomes over-geared, more like an overdrive, longer legs but it cannot get the ponies onto the road.



Personally, and I have a C5 with probably a few more ponies, I find the cruise speed almost adequate, 3000rpm is about 50mph, 16.5mph/1000rpm in top, 60mph is a little over 3500rpm. I prefer better acceleration in top (lower gearing) to ultimate top speed; if I had wanted a fast bike I wouldn't have got an RE. I shall most likely fit the larger rear tyre when this one has worn out. The small increase in outer diameter equates to half a tooth more on the gearbox cog. This seems to me to be the simplest and least expensive option as a tyre is an expendable item, they wear out anyway. This should give a mere 1mph increase in top at the same revs, changing the cog to 19T, 2mph. Hardly any difference and for me, not worth the effort taking the covers off.

[Graham43]

Thank you jefrs and you all. I think I will just replace the rear tyre with a larger one. Thanks again for all the advice.

[PeteF]

You must be a complete wizard with tools if changing an Electra drive sprocket is as simple to you as changing the oil.

[jefrs]

PeteF - oh well I'm supposed to be some sort of engineer. Getting things apart is relatively easy, getting them back together in working order is the difficult bit. Sometimes it helps to take photos as you dismantle.

[PeteF]

Ah but what sort of engineer?
I have a friend with a degree in mechanical engineering from Cambridge; very clever fella who can design machines, work out stresses and specify materials etc. etc. till the cows come home. Give him a spanner and he's sunk. I have to service his lawnmower for him!
Whereas, my Dad (who I got lots of my knowledge from) had no qualifications whatsoever and could fix just about anything using a lifetime's accrued knowledge.
I am wary of highly qualified experts.
As for getting things back together again; you just need to be methodical.

[Mark B]

As I've now ridden my 500 Bullet on the road I thought that one extra tooth on the gearbox sprocket would be good, but then I realised how much you have to do to get at the sprocket on an Enfield and decided to leave it as is. Then I noticed that our hosts have a step-by-step guide to changing the sprocket in their technical notes section. It's actually not that difficult, although maybe it'll take slightly longer than an oil change...