Phil Denton 5-speed transmission (road use)

Spargett · Post by **Spargett** » Tue Jun 29, 2010 4:09 am

I hear people mentioning the development of a 5-speed transmission for the 305's. I've seen many for race application with very tall lower gears. Came across a 5-speed made for road use. Looks nice, but better be at a cost of $2,518 USD.

http://www.phildentonengineering.com/pr ... p?pid=1236

e3steve · Post by **e3steve** » Tue Jun 29, 2010 8:12 am

Gerry Cain, +44 207 236 0096, sells a kit advertised as, quote, "commissioned for myself" in the UK VJMC Autojumble. Could be the same kit?

G-Man · Post by **G-Man** » Tue Jun 29, 2010 11:56 pm

Scott

Phil had a CB77 motor with one of these transmissions in it along with a NOS crank at the recent Classic Motorcycle show in Stafford near my home.

It looked very good but I'd want a whole bike for that money. Bernard Saunders does a racing version. I'm think of building a 350 street bike with all of the goodies and stripped for lightness, so I'm collecting some nice engine parts in readiness.

G

teazer · Post by **teazer** » Wed Jun 30, 2010 8:13 am

That appears to be the latest NOVA transmissions 5 speed cluster. As I understand it, Bernie Sanders had the first ones made by NOVA and were originally only available from himself. The ratios were identical AFAIK to the race kit trans.

I have no idea who persuaded NOVA to make a road version of the box, but it's available directly from NOVA http://www.novaracing.co.uk/honda-cb727 ... d-road.htm along with the race set up. http://www.novaracing.co.uk/honda-cb727 ... d-race.htm.

The one I have came from Bernie.

Gun · Post by **Gun** » Wed Jun 30, 2010 6:44 pm

I do not understand the % drop numbers on the website as I know nothing about transmissions. If anyone has a free minute to explain that would be much appreciated, if not, i totally understand and will read up about it online.

e3steve · Post by **e3steve** » Thu Jul 01, 2010 4:44 am

Looks like the drop in rpm between that and the previous ratio, Nick.

teazer · Post by **teazer** » Thu Jul 01, 2010 2:46 pm

e3Steve is correct. The percentage represents the gap between gears.

For example first to second on a CB27 is 40.4% and as one shifts from first into second the motor will now be running 40.4% slower in second gear.

So if the change is made at 10,000, the motor will drop by 4,044 revs as the clutch is released in second. That's a huge drop. The higher teh state of tune of the motor the less it can afford to drop. A street motor might be fine with a 4044 drop to 5956rpm but it is right off the boil and out of the powerband.

On a more highly tuned motor that would be a disaster dropping down so low.

So we want teh drops to be less than that and we want smaller drops as we go up the box because we have less leverage from the gearing in taller gears. That's great but if all the gears are closer together than stock it means that either top gear is lower or bottom gear is higher.

let's say that our box drops 64% overall (CB72) so we can do say 100 in top and say 36mph in low gear.

Race Kit CR box has a 42% overall drop so if it's geared fro 100mph at the same revs, it will now do around 60 in low gear which is what 2nd used to be good for, so it's like taking off in second gear. Great on a race track but horrible in stop start traffic.

So now we need more gears so we can retain some sort of bottom end for teh same top end. Like everything in motorcycle design - it's a compromise. The trick is to work out a combo that works best fr your bike, ridden the way you like to ride within the design constraints of the motor.