HarleyTechTalk

Technical Forums => Knuck/Flat Head => Topic started by: tenorhog on June 30, 2011, 01:36:15 PM

Title: 4 speed gears in a 3 speed case
Post by: tenorhog on June 30, 2011, 01:36:15 PM
Anyone done this to their 45?. The guys in Holland are selling it for 700 euro's

www.45parts.eu/45parts/index.php?item=&action=page&group_id=10000014&lang=EN (http://www.45parts.eu/45parts/index.php?item=&action=page&group_id=10000014&lang=EN)

I have emailed them for gear ratio's.
Anyone know the origional gear ratio's?
It might be really cool to do unless it's a 1 to 1.
Thanks,  Ben

[attachment removed after 60 days by system]
Title: Re: 4 speed gears in a 3 speed case
Post by: PC_Hater on August 23, 2012, 06:42:25 AM
I have looked through the info I have but can't find what the original ratios were.
The usual solution in the UK was to fit a 4 speed Triumph of BSA gearbox. Not rocket science, a bit of faffing about. Mine has had a 1950s Triumph gearbox for many years before I bought it.
If you want to keep the original look then the Dutch 4 speed conversion looks ideal. From old road tests I have read there were some big gaps between the gears so even if the top gear is still 1:1 the change would still be worthwhile. Then you can juggle engine, gearbox, and rear wheel sprockets to get top gear where you want it to be.
My bike does 80mph downhill and cruises happily at 60mph. Plan A is to twiddle the gearing a bit more at some later date.
If you can't find an old British gearbox then let me suggest Quaife Engineeering http://www.quaife.co.uk (http://www.quaife.co.uk) who do a very nice 5 speed gearbox that fits in place of the old Norton 4 speed gearbox. If you have the money they also do a 6 speed gearbox to replace the old 4 speed. The Norton gearbox was THE one to use. That is why so many UK 45s (and Indians) use Triumph or BSA gearboxes - cheap leftovers from people fitting the Norton box into their BSAs and Triumphs.

I use a belt drive primary on my bike too - works very well indeed.
Title: Re: 4 speed gears in a 3 speed case
Post by: 14Frisco on August 24, 2012, 12:35:23 PM
Quote from: tenorhog on June 30, 2011, 01:36:15 PMAnyone know the origional gear ratio's?

According to a manual:

Low Gear 2.47:1
Second Gear1.57:1
High Gear1:1
Title: Re: 4 speed gears in a 3 speed case
Post by: panic on August 27, 2013, 07:58:31 AM
I have some data on that conversion on my site here:
http://victorylibrary.com/tech/trans-ratio-45.htm (http://victorylibrary.com/tech/trans-ratio-45.htm)