103 conversion

[grbrown]

Good points Simon. What I am trying to put across is that the level of over-gearing on Harleys over the last 20 years is such that reducing gearing can be done without ending up by under-gearing them, especially on current 6-speeds. There is huge scope to achieve a compromise.

Some of us have been duped into thinking that low engine speeds at cruising road speeds is a good thing, while the only reason it is there is to appease the noise Police. IMHO the first part of a Stage 1 should be reduced gearing. That can still leave the equivilent of an overdrive top gear, but also increase torque at the rear wheel by up to 19%. And it is almost free!

[blackbike1450]

Thank you all!

The more I look at this the less convinced I am I "need" a bigger engine. I take the point that the 103 conversion is expensive and outside my budget, and when I think about it, what I am looking for is easier motorway performance, ie less revs for any given speed, but still with enough acceleration to pass slower vehicles (not many of those of course) and to be able to handle hills.

I have been quoted a good price to change to a two year old 6 speeder, but the difference in motorway peformance, whilst noticable was not that great, and I really like my 03 Ultra.

Maybe I will save the money for a trip to Turkey next summer.

[MadMax]

Judging from your goals of more acceleration but a lower cruise rpm you're going to need a 6 speed transmission. I believe that SE manufacture a 6 speed gearset designed to fit into the 5 speed case the ratios of which are similar to stock except for a 1:1 overdrive? Simon or Phil can probably correct me on this. The combination of this and switching your primary gearing from your present 3.15:1 to 3.37:1 is affordable and will give you more acceleration lower down whilst the 6th speed will reduce your cruising rpm. The 3.37:1 primary conversion is affordable and really works, I have fitted a few of these. Here's a comparison of speed/rpm ...

MPH 5th gear
3.15 3.37
RPM RPM

50 2050 2200
55 2300 2450
60 2500 2650
65 2700 2900
70 2900 3100
75 3100 3300
80 3300 3550
85 3500 3750
90 3700 4000
95 3900 4200
100 4100 4400
105 4300 4650
110 4550 4850
115 4750 5100

All you need to do this conversion is the sprocket (part no. 40269-85A) and a clutch basket (part no. 37846-99A) and of course the six speed gearset.

The question of more power can be addressed in many ways - how much do you want to spend being the major factor. If you're going to replace the crank with a longer stroke item then the options are limited by the size of your wallet. A well set up 95" can easily surpass the standard SE 103 kit in every situation you can think of and will cost nothing like the 103. On an Ultra you'd be exactly where you want to be with a set of Woods TW6 or Andrews 21/26 cams, SE cast flat top pistons and mild headwork to match the cams.

[Phil]

Originally Posted by Phil

Now fitting a six speed & lowering the primary gearing can give a result.

Originally Posted by MadMax

Judging from your goals of more acceleration but a lower cruise rpm you're going to need a 6 speed transmission. I believe that SE manufacture a 6 speed gearset designed to fit into the 5 speed case the ratios of which are similar to stock except for a 1:1 overdrive? Simon or Phil can probably correct me on this. The combination of this and switching your primary gearing from your present 3.15:1 to 3.37:1 is affordable and will give you more acceleration lower down whilst the 6th speed will reduce your cruising rpm. The 3.37:1 primary conversion is affordable and really works, I have fitted a few of these.

As have we. That is correct.

[simonDyna]

There are quite a few 6 speeds that offer 1st-5th as stock gearing (1:1 in fifth) and 6th as 1:0.89 or 1:0.86 when used with a standard 25/36 primary. By adjusting the primary ratio you can then bring the overdriven 6th gear back towards 1:1 for increased acceleration.

[Steppenwulf]

I'm really getting a lot out of this thread,
thanks for sharing the knowledge around,
it's all good stuff.

[grbrown]

Originally Posted by Steppenwulf

I'm really getting a lot out of this thread, thanks for sharing the knowledge around, it's all good stuff.

Jon,

If you give us your money we'll get on with it....

[Harleyrider1450]

Where do people get the idea that H/D's are over geared ? The last 3 i have owned pulled perfectly ok in top even two up and thats just with a stage one , of course it's up to the individual to decide what course to take but i was once told the more you tune the less reliable it becomes ,I personally cruise around 120/130kph and at times wish the gearing was a tad higher but for day to day use i'm quite happy with the set up.

[MadMax]

Originally Posted by Harleyrider1450

i was once told the more you tune the less reliable it becomes

The modifications that were mentioned can hardly be called tuning - merely correcting the seriously detuned state that Twin Cams are in when they leave the factory. For example ... cams designed to keep the emissions down and not optimise valve events as they should, cylinder liners bored to 88 inch instead of 95 inch, restricted airflow on 99-06 heads etc. The level at which reliability is negatively affected is a long, long way away yet .. All of the ideas in this thread are very conservative hence perfectly safe.

[grbrown]

Originally Posted by Harleyrider1450

Where do people get the idea that H/D's are over geared ? The last 3 i have owned pulled perfectly ok in top even two up and thats just with a stage one , of course it's up to the individual to decide what course to take but i was once told the more you tune the less reliable it becomes ,I personally cruise around 120/130kph and at times wish the gearing was a tad higher but for day to day use i'm quite happy with the set up.

Read #11 above!

If I have to explain again you won't understand.