Alternative final drive

[MickB]

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Hi Folks,
I have been toying with the idea of swapping the S final drive to one from an RT for a while now and have finally got round to it having found a final drive and cable for a good price. As can be seen the final drive fits perfectly, as is to be expected and IMHO doesn't look to bad. The change in ratio is from the original S at 2.75 to the RT final drive at 2.62.

Riding the bike is for me a great change it feels much less busy and more long legged, which is what I was hoping for. I can feel no loss of acceleration tho' there must be some due to the changes made but in the real world with no other bike to compare it to I can't tell. I did however have a new map installed over the winter which may be masking any potential losses. (Done by Junction 33 near Lancaster, excellent service and I'm very pleased with the end result. The owner also owns a yellow S which he used to develop the map for our bikes)

The only fly in my drink at the moment is that the speedo is no longer working. I cannot use the original sensor cable from the S in the new final drive as the hole for the wheel sensor is simply too large. I have used the RT sensor cable which also uses two wires and connected this to the bike loom using BMW connectors. I am sure that the polarity is of all the connections is correct, mainly because the connectors can only fit one way.

My S does not have ABS, the RT unit does have an integral ABS ring it is the first generation none vented final drive from around 2007. Whether this is the cause of the problem is yet to be ascertained.

I have now reached my knowledge limit I'm looking for suggestions as to who may be able to assist as electronics sensors and pulses are really not my thing. Alternatively if there is an easy solution I'd be glad to hear it. Equally if this set up will never work for what ever reason let me know and put me out of my misery and I'll go back to stock. Shame as I was looking forward to some quality European holiday time.

I look forward to hearing from someone

Thanks in advance

Mick

[dave the german]

Hmmm, quality European time - well, you've got a couple of years to get it sorted Interested in more details about Junction 33 as I'm looking to get my 12S mapped

[MickB]

The guy who works there is called Andy and it's his own business. The workshop is immaculate, eat your dinner off the floor so to speak. He is very busy which I took as a good sign. There is a waiting list for his services. He is a couple of miles from J33 off the M6 as the name suggests.

I needed two visits one to see what map is in the bike, he does a download of the original map while you wait. There are subtle differences between the maps He then does some lap top magic while you are away and then dynos the bike and downloads the new map. Take this how you want, dynos being dynos and all that but I went from 115 to 122 at the rear wheel. There was corresponding increase in the mid range throughout. I haven't really put things to the test but it just feels stronger and more lively. I have no idea of whether or not fuel consumption will be affected.

One small bonus is that the idle is now much better and steadier. Your O2 sensors will be disconnected if you have this done so you will to remove the O2 sensors as the wires are now not connected to anything and get some blanking plugs for the pipes (plenty on E bay) and some means of masking off the connection for the O2 sensors to the loom which I have not yet done.

My set up is an Akra pipe with the cat removed and a standard air filter. The end result with a standard exhaust will possibly be different. The price was £350 including VAT. Before and after maps are supplied along with the traces for various percentage of throttle openings. This was cheaper than BSD in Peterborough and 400 miles less driving. All in all I'm well satisfied.

Andy is a Boxertrix member but I can't recall his user name.

PM me if you are coming over to have it done, I'm 5 miles away from him and I'll put the kettle on. Hope this is of use to those of us who live OOp North.

Whilst on the subject of good guys, I had my rear shock rebuilt by TW Suspension in Preston. When the shock was returned to me it looked like new. He also does a very good ride in ride out suspension set up for £40 during which, I was embarrassed to discover that I had been riding around with very little rebound damping

[dave the german]

Thanks for that Mick. I have an Akra end can. Had loads of problems with the running of my 12S (vaguely documented here but sorted by Andy at Williams BMW - that again is another story!!) I have a Power Commander for my bike but have some BOS downpipes which I want to fit and do away with all external wiring. I travel down the M6 every day with work to Skelmersdale so when this madness ends I'll be down to get mine sorted. I've heard of the positive results from Hilltop but it's further to travel so a recommendation for someone closer is much appreciated!! get the kettle on!!