Middle gear case

[Jonesy]

Pete, thats gold, I've saved it for later reference if I ever need it
Jonesy.

[petejw1966]

[/quote]

was doing a bit of reading on the middle drive and found out that those numbers scribed
on the case are from factory and relate to the drive pinion shim
heres a link

http://www.ringler.us/xs1100/ShaftDriveManual.pdf

chapter 9 pg 43.

[steptoe]

with my orig middle box 79-96  tacho read 4000rpm@ 100klm,,

after fitting the current one, 79-95  tacho reads 3500rpm @100klm

with EVs' box having 79-99,, I guess some close riding excersizes are in the sights
 
following the numbers,, if they mean anything, EVs' should run higher again

[excess.11]

These Tacho s are electronic guys. As our bike get older  the " values " of the components may vary slightly .Capacitors , coil resistance , value of frequency output from the alternator etc . Might pay to keep this in mind when getting down to tin tacks about one versus the other.

[melbxs]

My point is that if they are accurate +/- 4% then there is the difference between the 2 bikes. There's probably no difference in ratios at all.

The difference could be +2% on one machine and -2% on the other. 

[steptoe]

as accurate as anything that's 30 yr old  ,

mine is rock steady no matter the reading,, can't say the same for the speedo,

[melbxs]

How accurate are these tachos?

[steptoe]

my current middle drive has 79-95 ecthed in,,,

my original box has 79-96 ,,

be nice to know what it means,, maybe malpit can shed some light on

will send a thingy and see

[Eveready1100]

After having a bit of a run alongside Steptoe & Maksy last week, I was trying to pick a speed at which both the speedo & tacho settled enough for an accurate reading. My result was 120kph = 4250rpm.
Steptoe advised me later that his was doing 4100rpm at that speed. Both our bikes have 100/90 -19 and 130/90 17 tyres fitted so there shouldn't be too much difference sizewise in that respect.
How does everyone elses bike compare with that.
He had changed his middle gear case some time ago and by the looks of it, has resulted in getting one with a slightly lower ratio in it. We had a bit of a chinwag before setting off and Maksy pointed to an etching on the backside of my middle gear case. It appears to have the numbers 79-99 scratched on it. My case is the original, so i was wondering if they might have been marked at the factory like this?