The starting point.

So, to begin take one cosmetically challenged 1981 GSX1100 ET. I can clearly remember the first time I saw one of these when I was about 14 years old. Brand new, big, chunky, industrial looking thing with a strangely Art Deco rear light. The bloke riding it came out of the lights turning right on a damp road. He opened the throttle and it wagged it's arse all over the show. Fair play to him, he kept it on and eventually it sorted itself out 30 or 40 yards up the road. It made quite an impression, and I knew I wanted one.

Thirty years later bought one in a sorry state, but basically sound. I sorted out the electrical gremlins, changed the brake pipes and some bearings, tidied it up a bit (no, really, you should have seen it before!) and took it for an MOT.



I used it for a year and I was expecting some 'issues' to show themselves but nothing did. Squeeky (the cat) decided that old Suzuki's were cool enough to be an acceptable perch, and the year passed.

 Time went on an Squeeky grew fonder of his bike. 

The MOT duly ran out and with Mike's 'assistance' it went up to the container to be stored until I got round to starting the restoration.

It sat in the container for a year or two gradually getting  buried under work and bike stuff. During that time odd bits and bobs were bought still with the intention of a restoration 'at some point'.

I took on a small unit for work and moved all of the stuff out of the cramped container into the unit. Having the unit meant that I could seriously consider starting work on the restoration. Then this came up at the right price, and obviously I couldn't resist. Enter ET number two. As it was pretty much exactly what I intended for the blue ET it created a bit of a dilemma. There doesn't seem much point in having two mint ET's so what should I do with the blue one?

After some thinking and running through the options (some more ridiculous than others) I settled on a quick road bike. To get that I need it to handle well, have loads of torque, retain the ET's look and yet be a bit different. I also want to include modern electrics and have a decent choice of tyres.

There are quite a few elements to this which I still haven't made my mind up about, but there's plenty to get on with in the mean time.

The first step is obviously to strip it down. It's also the quickest and easiest part of the rebuild plan.

It quickly starts to look very bare and narrow. With the bodywork off of it you can see just how basic these old bikes are.

At this stage a few more things on the 'must have/do' list are coming to mind. One of which is getting rid of as much clutter from above the swing arm pivot. Relocate the battery and clear out some of the other bits.

Getting the engine out can be a bit of a fiddle, mainly because of the weight. These air cooled engines are renowned for being over-engineered. One reason why so few ET's survive today is because the engines are very popular with drag racers as they could be tuned to ridiculous levels. Until Suzuki launched the Hayabusa the weapon of choice for most was the GSX1100 16 valve engine.

With everything off the frame looks quite flimsy. It's ready to start getting bits on for a dry build, but there's a fair bit of parts gathering, measuring and head scratching to do first.

I will at some point add explanations of the basic principles involved in the geometry changes. In the mean time, Google is your friend as there are some great resources on the internet covering motorbike dynamics and geometry.

There are quite a few old Suzuki's about which have been modified or upgraded in terms of running gear. The simplest solution is to bolt on the parts from a more modern Suzuki and off you go. Doing that will improve things, but only in terms of spring/damping rates and tyre choices.

I want to take it a stage further and improve the overall handling of the bike, so I need to change the bike's geometry. The basic changes that I'm aiming for are to reduce the trail to give it a sharper turn in, along with lowering the bike by around 50 mm to drop the centre of gravity. I don't want to sacrifice too much in the way of straight line stability though, so I can't reduce the trail too far or things will get very 'twitchy'.

This illustration gives the basic angles and components which give the rake and trail.

The easiest example to explain trail are the rear wheels on a shopping trolley. Because the centre of the wheel is behind the line of the swivel the wheel naturally flicks back to the straight ahead position.

If you look at the blue lines you can see what will have to be changed to reduce the trail and the wheels natural tendency towards the straight ahead position.






The ET has had the trail reduced by putting the spindle in front of the fork leg which has added another offset. So on the picture you can see the headstock line in red. The offset is the distance between the red and blue lines, and the additional offset is the distance between the blue and green lines.

The trail measurement for a standard ET is 103 mm.

So the next step is to get some forks, a swing arm and wheels sorted then I can work out how much things need to be altered by to get what I'm after.

From the rough figures I have I know I'm going to need to balance the work at the front out by extending the wheelbase rearwards. Several options were being considered for this when a JMC arm came available. This will tick all the boxes, and I'll just need to work out rear shock length once I have the front sorted.

The forks are from a GSXR1100 M, the yolks from a WP and having these in place will allow me to take all the measurements.
It also allows me to sit the bodywork on and see how it looks. This is what I'm going for, with a UK spec tank and the headlamp mounted low.
I'll use clip on bars and mount the digital clocks into the back of the headlamp cowl. Once the risers are gone (new yolks to be made) I think it'll give the top of the bike a clean line.

I also tried an export tank, but it didn't look quite right. Not really 'chunky' enough to suit the bike.

It's starting to take shape, and I thought I'd do a standard bike to modified comparison.
It's definitely going in the right direction. So the next phase will be taking the measurements and working out what needs to be changed at the front.