Part 3. Always bloody rules.

It’s confusing; I’m building an Endurance Katana to race and yet I have found myself looking at Brake calipers from a Pan European, wheels from a Triumph Speedmaster and even headlights from an FZ750 when searching for parts. Well, I haven’t gone potty; it’s all to do with the rules.

Rules. Does anyone like them? If you’re going Classic Racing, you’d better get ready to drown in them! Getting this Katana ship-shape and legal for Spa has required about as much time reading and absorbing the regulations as it has in the garage so far.

But, surprisingly, for something that is basically “being told what to do” (widely unpopular) the process turned into something I enjoyed. It’s a challenge; finding parts that get as far as the rules allow, whilst still paying some respect to the (not unlimited) budget. Thanks solely to the Internet, it’s been a 1-man scrapheap challenge without ever needing to leave the kitchen table!

I think the rules for the UEM’s Maxi Classic Class are pretty good. They make things as simple as possible for the competitor, but with due reverence to keeping things “period”. It’s created a pretty level playing field without too much restriction, yet still allows a bit of creativity to flow through your build.


1. The motorcycles have to be built before December 31st 1982 and have a minimum of two cylinders.

 Well, we have recreated a 1982 GSX1100 Katana using a 1982 750 Katana frame with a 1982 4 cylinder GSX1100EZ engine (both identical parts to the 1100 Katana barring really teeny differences) So, we’ll hopefully not be bounced for that!

There is no limitation as to the total cc but it has to be higher than 340cc. For the engine, particularities from the mass-produced motorcycles need to be retained, such as: numbers of valve, number of transmission ratio, number of camshaft etc. If certain parts had to be replaced, they should be similar to the original ones.

Nothing here worries me. We have plans for reground cams and oversize valves slotting into the head from an EFE  which although a slightly later model also fits the “very similar to the original” clause, as it goes straight on. It is therefore “very similar” to the original! (just with a shitload more power!)

 2. The carburettor has to be with round throttle slide.

 For round slide carbs the GSX1100 racer’s perfect choice is a bank of Keihin CR carbs in either 33, 35 or 37mm, depending on the state of tune. We looked fondly at 35’s, and had them delivered soon after making the decision from the font of all things good in the world of carbs – Allen’s Performance. (thanks Steve!)

3. Front fork tubes of maximum 42mm diameter.

 Unbelievably Katana forks are just 37mm, and that’s for a 230kg plus bike. Not ideal. Racing on those would be like trying to make a Pig dance on stilts made of McDonalds straws. They had to go.

I spent days trying to find out what bikes have 42mm forks. It took ages, because there’s actually very little information on fork diameters published freely. I was getting bits and bobs of info, but what I really wanted was to find the as of yet non-existent site

Turns out that the easiest way I eventually found is to abandon searching for the forks by size (nobody lists second hand forks that way) and instead use the search term “fork seal 42mm”.

This worked well in finding bikes with 42mm forks, but the choice at the end of that search was limited; CBR600F4, CB900 Hornet and DL650 V-Strom were about as good as it got from a much longer list of bikes which weren’t fit to grace a racing Katana (Kawasaki’s VN1500 Cruiser springs to mind, although the ground clearance with such long forks could have been awesome…) In the end I couldn’t find a decent set of any of those, so…

…I had wanted forks as big as the rules allowed, so I hadn’t previously searched for 41mm. But when I did the world of choice opened up! Decent options started to fall thick and fast into my lap. A selection of which were FZR1000, Thundercat, Bandit 600, SV650, ZX6R, GSF650 and importantly – Slabside GSX-R750.

The Slabside GSX-R750 is of the Suzuki generation immediately after the GSX range – a few calls revealed that the GSX-R forks and yokes would slide straight into the Kat’s headstock. Attracted by the simplicity of this I picked up a set of GSX-R750 forks and yokes for £30 off eBay.

Cheap forks and yokes, but they’ll get the expensive treatment.

4. Wheels; 18 inches, rim width of 4 inches maximum.

The Katana shared OE wheel sizes with the GSX1100EZ that I bought as a donor bike, but awkwardly neither of them are 18”! The 19” front and 17” rear have consequently already been offered up as a gift to the gods of moto-recycling (well, swapped with a bike breaker for some other bits)

So, searching for wheels I momentarily forgot about the budget and looked at the sexy stuff first:

Pure race wheels

Dymags – The H-section ones are the ones that really “fit” the build, and they’re hens teeth in good used nick in the 18” that we need. The last pair I saw sold went for just over £500, which may not seem bad; BUT – buying any used magnesium wheel of unknown history needs to be undertaken with care, it’s essential to budget for crack testing before using. So the best ones to buy will have a very recent record of this being done already, which will doubtless be reflected in the price.

Can’t be bothered with all that fuss? – buy new. The Classic H-sections Dymags are also available new for around £2,000 from Dymag’s distributor in the UK, PDQ in Taplow.  After looking, I didn’t buy any of these. Used = too risky, new = out of budget.

Astralites – Then I looked at Astralites, which are again mega-rare in the right sizes, and in the type suitable for tubeless tyres. Astralites come in 2 types, rolled and unrolled edges – tubeless only work on the rolled edge model.

Shortly after starting the search for wheels some perfect sized ex Classic Phase One Astralites (which had raced at Spa!) came and went for just over £500 without me securing them. I was momentarily sad.

Rejoining the search for second hand Astralites, lo and behold, I discovered that they are being made brand new again in the UK. Paul Allender, an ex employee of Dawson Harmsworth that made them back in the day has secured the rights to the name and is producing them for the burgeoning classic scene. He’s a top fella, and I had a chat with him about what I was after, and for £1,100 or so I could have been wearing a set of boxfresh ones on the Katana.

Boringly I’ve sat on my hands and not bought them. With the engine build lurking, wheels couldn’t sensibly be allowed to take that much of the budget at this point. Although I haven’t bought a set yet, something keeps making me look at these in the Gold option and going mmmm….(if you want to help us out with a set, or buy your own and help support a lovely little piece of racing history please feel free! )

So, looking for realistically affordable (and boring) OE wheels took me through a jungle of opportunities from FJ1100 to Triumph Speedmaster, VF750 Magna and Cagiva Canyon. Mostly they weren’t matched in the sizes we needed for both the front and the rear, so we’d have needed an odd pair. Most of those anyway just wouldn’t look right; an XJ900, FZR400 or ZX10 wheel on a Katana? – mmm, no thanks.

So, after all that hunting about, guess what we were left with to make a perfect pair? (and I really did try and be more expansive in my choice than this) Yup; Slabside GSX-R!

Not only would these fit the forks we’d bought, they are bang on the right size at both ends, even offering a choice of fronts in 2.5 or 2.75×18, with the rear from the 1100 (and later 750 Scottie says) being an 18×4.0.

There’s almost a sense of “Karma” in using standard Suzuki Parts on the build and I’m not unhappy with the choice at all; it just feels right. Especially right considering I got change from £100 for the pair I bought…!!!

In other positive news relating to this choice, I’m also hearing that the Slabby swinging arm should be an easy fit into the Kat frame (maybe even a straight bolt up), which means the rear wheel would be a bolt up job too. Easy. I like that. The one job there will be is to weld shock lugs on for the twin shocks, but that’s no biggy.

Gold Astralites….mmm (told you)

 5. Brakes: original fixed disc or semi-floating with a maximum diameter of 300mm. Floating disk are prohibited. Calipers with 4 pistons or more are forbidden as well as master cylinder with a separated oil reservoir of recent construction. (Update – rule change for 2014 – 310mm discs now allowed)

Discs.  Suzuki and Kawasaki shared an OEM brake supplier back in the day, which is why the 60mm hole centre discs with 5 bolt 80mm PCD (Pitch Circle Diameter) that the slabby shipped with, is also a straight fitting home for very many Kawasaki discs right up until ZX9R E model of the early 2000’s. We need 310’s, the ZX9R “E” discs are just that – we’ll be using these. We had bought 3 pairs of KR1-S discs (300mm) but the rules changed from 300 to 310mm max size at Xmas, and rendered the bigger disc as the best option.

Calipers – what’s one less than 4? – 3! Correct. And amazingly there is a 3 piston caliper out there, which I would never have guessed before needing to make hay out of the rule book.

The ST1100 (Pan European) had sliding pin 3-piston calipers fitted between 1995-2002 (I’ve since found out that the Honda CBF1000 still ships with these calipers – I ride on them at the Haslam School every week in the Summer, and they’re good brakes – very good brakes!) Although this discovery initially excited me (which in itself is quite sad), examining the linkage that attaches and surrounds the caliper started to make my head hurt. It’s typically Honda in it’s complexity, and looks like it needs a union with an ABS linked brake system or something very unracey. Idea ditched.

2 piston calipers consequently appeared on the purchase radar and with a tip off from Scottie, I took a look at brakes on something not a million miles away from a Pan European; an NTV650V Deauville!

Now, I’m not being horrible, but I’m not a Deauville kind of guy. What I am is a Brembo kind of guy. What I didn’t expect is that Deauville’s from 2001 to 2005 shipped with very smart 2-piston sliding pin Brembo calipers, even finished in Brembo’s best gold paint!

For £50 I snapped a pair up, including braided lines. (Am I starting to sound cheap? You wait until you see why – it’s the engine that’s getting the dough)

Brembo loveliness - wasted on the Deauville they came off? Depends if you love Deauvilles I guess?!
Brembo loveliness – wasted on the Deauville they came off? Depends if you love Deauvilles I guess?!

The forks have mounting points 5mm different from the calipers, so we’ll need something made up to make them fit, but as the Slabside GSX-R calipers are 4 piston, I can’t just use them anyway.

Master cylinder – AP Lockheed make something that looks period (because I think it is!) which should do the job well, they’re around £200 and will be a top piece of kit. I may, later on, plump for  a set of the AP Classic twin piston calipers – but I am tightening the old belt ready for engine spend, so once we’ve counted what’s left  after the mill has eaten, we may spec the old girl up a bit.

6. Special frameworks are allowed if the coupling framework-engine can be proved with historical documentation.

This rule is probably aimed more at the P&M, Bakker, Harris or Moto Martin framed specials, but as we plan to de-lug and brace our frame, I’ve taken it on board and looked into the Katanas that raced back in the day.

Wes Cooley’s Yoshimura Suzuki shows signs of de-lugging and bracing, in fact of complete frame redesign on some variants. Should therefore the technical police come knocking, about our little bits of extra pipe welded here and there to stop the frame from snapping, we’ll Google a bit of historical provenance and hopefully send them packing!

7. Specifically NOT allowed; Data recording systems, forced induction, fuel injection, slipper clutches, carbon exhausts, carbon accessories, piggyback reservoir rear shocks.

So, in a nutshell you can see particular attention is paid to keep the visual bits like the wheels, tyres, brakes and suspension looking period, (and not made of carbon fibre either!)

In the pit even tyre warmers are banned, as are slicks and wets. You may be surprised to hear I’m happy with that – but we’re not racing chequebooks, and with every tyre combination you allow, you need another set of wheels. The rules provide for making sure we can do with just 1 set. In my (budget strangling) world, and with an engine still to build, that’s all cool!