Modifications 850 Le Mans III '83

 
Oktober 2005
Jan Sybren
 

 

Modifications

The overhaul of the LM2 came to conclusion wiith the first successfull 10.000km in 2003 (the disappointing Minardi action at the ring of Antwerp, was a not related incident). This gave time and "budget" to the original plan to make a cafe-racer of the LM3. Usually a cafe racer is 70% smuck and 15% story and 15% improvement (because the unnecessary parts are removed). And of course I should have sticked to this concept. But since I had been riding on the Sport 1100 of a friend I figured a better front fork and parallel rear are really making sence, so ..

I bought a Giovane F.I.T. rear suspension



This system comes relatively close to the parallel swinger of the Sport 1100, with this difference that it is still a stereo shock bridge.
Apart from having a parallel swing-arm, the advantage of this rear swing is more space for a 160/60 R18 tyre, in order to have the same tyre size as the Sport 1100 (With a lot of hassle as I experienced later).
All that was left now was a good front fork. I ran into a standard Daytona front complet with Brembo four cylinder gold lines, so this would mean a further improved front.

The swing is not exactly parallel. This leaves a little of the cardan-effect. Because of this it is possible to use shocks with a bit over-length ( I have 20-30 mm over-length) The more the spring compresses, in my configuration, the more the axles are becoming parallel.

The hype for modern Superbikes is not so much the weight, but even more the weight concentration. This is interesting because on this point I scored on several points

  • Lighter rims (both around 1 kg, but this is an estimate because the tyres were on theLM3 rims)
  • Lighter rear swing (several kilo's)
  • Frame tubes behind the shock connection will be cut-off
  • Battery from 32 Ah to 9 Ah (ca. 9 kg to 3.4 kg)
A furter improvement will be a standard Valeo starter vor the Guzzi'e. This starter requires only a 9Ah battery and the type from Yuasha is only 2.4 kg in stead of the 8.8 - 10.2 kg of the 32Ah battery. Also the Valeo is lighter than the Bosch starter

The final weight reduction (measured)
 
part original
[kg]		 modified
[kg]
front-fork complete 29 29.2
rear fork complete 32 30.2
battery 10.2 2.4
startermotor 4.0 2.8
frame parts and centre stand 3.5 -
Seat and rear-end 3.5 1.5

The weight reduction in total of this part of the job is,

16.1 kg
The weight is devided as front/rear = 102/108 kg/kg
My good old LM2 is devided at front/rear = 95/130

I think the LM2 has an advantage because of the smaller tank. Both bikes were measured with a full tank. Further the wheelbase of the LM3 is longer and in my case the longer rear shock bring weight to the front (only very little of course) 
 

Picture of the modifications

This picture shows the bike as I put it together in September 2005. I managed to realize all ideas from the list above and in a functional sense the first 300 km were not disappointing. It is a totally different bike and the expected improvement in road handling seem completely, what I expected. Although the higher seat (approx 40mm higher) and the lower bars (also 40 mm but then lower), give me the feeling of a head-first canonball :-).

I still have to get used to the improved road contact and I dont have a good feeling which tyre would loose grip as first. And this makes me reluctant in pushing the bike trough the corners. On the other hand, the temporary missing speedo-meter does not make it easy to compare this bike with its original-state LM2 brother.
Coincidentally, I found the same experience written down in an article in the german magazine "PS" Nr 9 September 2005. Here the author tests the Dynotec LM1 Retro-racer, which has more HP than mine, but has a very comparable handling set-up.
This picture shows the most succesfull part of the modification. The Wilbers shocks and the FIT rear swinger (as described above). I think the shocks give the potential improvement of the road contact at the rear and make the bike feel very stable in corners (small and long) and on the flat-out straight. I have not felt one single wobble, weave or what so ever. But it is the parallel swing that makes it possible for the shocks to work fully under al circumstances, especially in the corners.
The front-end is based on a MG Daytona fork (42 mm).
Of course it is a great improvement over the 35 stock fork or 38 Marzzochi that are on the LM2 and was on the LM3, but with the complete improvements, these forks are the parts that might be the first for some re-trimming (Other springs I think and an damper adjustment).
But the fork carries great brakes, with these 4 piston Brembo gold-line calibers and semi swimming discs.
The Rev-counter and oil and battery lights have remained. The contact is a temporary solution I have to find an other place for this one. Th speedo will be mounted on the clutch handlebar.
The rear brakes with the V11 webmaster-cilinder and Tarozzi controls. Please don't pay to much attention to the rusty busso exhaust. It is a temporary solution, just as the cover plate that can not be mounted over de side, because the brake-cylinder is in the way.
The 160/60 rear tyre with the traction-line. 
The seat is a quick fix with a piece of left-over aluminium. It does give a very agressive look to the bike. Combined with the rusty exhausts it looks like a RAT-RACER. And that is what we al will end-up
Here you see a closer look of the carbon-epoxy battery-plate that connects the gearbox to the frame. This plate is with 8mm and 16 layers of 200gr/m2 endlessly stiffer than the usual sheet metal plate. Whats more, carbonfibre damps the vibrations and indeed this bike has much less vibrations than it used to have 
A closer look at the parallel swing and CV-joint.
The aluminium swingarm compensates not only the torques, but it is much lighter than the 18.2 kg heavy stock steel swing-arm.
Here a close look at the stiffening plate (carbon-epoxy) that connects the distribution cover to the upper frame tubes. It makes the engine a part of the stiffnes just as in the modern V11's

 
 
Back home