Super but not stock
For a clubman, often standard is enough – for a good rider however, something more might be needed.
A racer has needs, a good racer’s needs are often more than standard machines can deliver… Check out this KTM.
As a reasonable club competitor I don’t mind admitting a super-tuned motorcycle is more of a liability to me than a benefit. Doing this job I’ve enjoyed riding all sorts of different machines from super-tuned to standard in all sorts of events, and the standard ones are often much easier to make go faster… but that’s me, wobbling round at the back – up at the sharp end where riders can use extra performance it’s a different story.
A bit more power than standard, sharper handling or some better suspension than the factory ‘one-sizefits-a-reasonable-selection-of-riders’ can really make a difference to the finishing order.
CDB looked at Mark Gessey’s standard spec KTM a couple of issues back and alongside it was this considerably more trick race bike which reflects his attention to detail just as much as the stock rebuild did. Based on a 1987 350 KTM but with a 1989 engine in place, the bike has uprated suspension to help the uprated engine deliver the goods on the track.
Starting this project by completely stripping the frame Mark checked it closely for any damage and once pronounced sound it was powder coated to KTM’S colour and new bearings were pressed in to the steering head. At the other end the standard swinging arm was cleaned up, blast cleaned, new bearings fitted to it too and into the frame it went.
Obviously a frame and swinging arm needs suspension at the front and rear and in the race world the former Dutch company White Power is a popular choice for those looking for something special. It is also a fitting accessory to use on a KTM as the Austrian company bought out the Dutch organisation in 1999 (shortened to its WP initials) – the suspension still is a force to be reckoned with in the modern scene.
With such suspension there is no real ‘standard’ setting, an obvious statement really as what would be the point of standard trick suspension? So, the front forks are built to works specification while the rear end of this single shock system is matched to Mark’s race weight by suspension expert Perry Leask at HM Racing.
The Leask name is not unknown in the world of MX with Perry having been immersed in the sport since he was a small child notching up more than the odd British championship title in youth and adult disciplines, and his father Brian not only being a top scrambler but UK Husqvarna distributor.
We digress slightly... Disc brakes started to appear on dirt bikes in the Sixties, yes, that’s right, as far back as that, they weren’t fully understood in those days but there are Mxers, grasstrackers and trials bikes all with these new brakes. Once the tech bods started having a look at them and sussing out
what was needed the MX world got brakes…
There are discs either end of Mark’s KTM, they are the standard hubs blasted and cleaned before having the original rims laced back in with new spokes. New bearings too make sure the wheels stay in line. Do we need to say the hydraulics and calipers have been sorted too? Keeping the rims up off the track is the job of Michelin tubed tyres.
With the chassis kind of done, Mark turned his attention to the engine which is a water-cooled 350 two-stroke unit. Let’s get the obvious out of the way first… he’s gone through this engine with a fine tooth comb or probably more accurately with the attention to detail he gives to the MGB cars he restores for a living.
Now the backbone of any engine is the crankshaft, if this isn’t spot-on then there’s no point in doing anything else, the shaft in this bike is fully rebuilt but it wasn’t the first task to be done… no, that was the gearbox.
As Mark and I chatted about the bike, he explained the gear shafts and selector forks had been hand polished and the dogs on the cogs refaced to relieve stress and help in their engagement. Once this was done there followed a lot of dry assembly to check each gear dog was fully engaging in its slot.
“It is popular to undercut the dogs but that is a bit short-term and okay for a factory with access to lots of replacement gears,” says Mark, “don’t get me wrong it is a good engine building practice just they will need changing regularly.”
Once happy with the performance of the gearbox Mark could assemble the cases and turn his attention to the barrel. The barrel is altered to reflect the factory
❝ CDB looked at Mark Gessey’s standard spec KTM a couple of issues back, and alongside it was this considerably more trick race bike which reflects his attention to detail just as much as the stock rebuild did. ❞
race team spec porting, something Mark took from a special KTM barrel by Dutch master Kees Van der Ven.
There’s been quite a bit of attention to the porting apart from using the dimensions from the works barrel. Most people reading this will understand the importance of matching the transfer ports to those in the crankcase. Yes, the standard ones are okay, but for that little extra performance then matching to the ideal – a term called ‘blue printing’ which comes from the old days when a designer would finalise the dimensions on a blue-printed drawing and this would represent the ideal dimensions for a component without any manufacturing tolerances – gives just a little bit extra.
Another area which receives attention is one which KTM owners will know as ‘Dimension X’ which sounds like some form of Fifties Sci-fi series at the cinema but is actually the distance from the top of the piston to the top of the barrel liner. This dimension is critical and is adjusted by selecting base gaskets of differing thicknesses to raise or lower the barrel height.
Adding bits on the side of the engine, bits such as the ignition and primary drive, also displayed the thought gone into this race engine by its owner. Reflecting the changing needs of MX Mark has fitted a mid-90s clutch arrangement which takes the abuse meted out to these components better than the earlier one. The unit was developed with the assistance of EBC – the brake specialist – so has their friction material on the plates and gives increased performance. Mark has also mixed spring rates in the clutch by fitting three heavy duty and three standard springs to the six-spring unit.
On the other side of the engine, where the bit which makes the spark sits, is a Motoplat ignition unit. Given the level of work on this engine and the time it has taken to do, when the owner says “a lot of time has been spent on setting the ignition…” one can assume it is time consuming.
“The thing is,” says Mark, “KTMS don’t like the ignition being out of the setting range and modifying the compression ratio and Dimension X means it needs care in the setting.”
With the engine in the frame Mark fitted a Dynoport exhaust, a USA performance item, matched to a modified DEP silencer. The exhaust system has a slight modification to it so a fuel/air sensor can be fitted when hooked up to a dyno for final tuning.
“Once I got the 38mm Keihin carburettor on I went along to Kelvin Tatum’s place and hooked up to his dyno. This takes a lot of the guess work out of settings and ensures things are working properly.”
With all this extra tuning going on some attention has been paid to the liquid-cooling system and an oversize radiator is in place of the original. This is a GMX radiator, all aluminium, which saves weight as well as dissipating heat a bit better, and flowing through the pumps and pipes is Evans waterless Coolant.
Making a bike look good is down to the availability of plastics… plastics is the generic term for mudguards, tanks, radiator covers, numberplates and that sort of thing, it can include glass fibre too but that would be for much earlier machines than this. In the plastics world it’s not long before the name Acerbis comes up. The Italian company have been supplying aftermarket, original equipment and replacement plastics for a long time and if it isn’t in their range then it’s likely not available anywhere. The plastics on the KTM are Acerbis but the rear mudguard is a rare original and pretty much unobtainable. Luckily it was in good order and able to be fitted back on. Lee Rudd at LR Designs did the graphics and Frank Thornton at MXA did the seat cover, both finish the bike off nicely.
As we looked at Mark’s bike I asked if there was anything I’d missed asking him? “Well, the handlebars are Renthal,” he said, “I’ve Magura controls on them and what you can’t see is the airbox is drilled to increase the air flow. I’m on Castrol and use VP Race Fuels as it is constant, pump fuel can differ depending on the time of year which alters the fuel/air mixture a bit during the season.”
We were speaking with Mark at the end of the 2019 season and he – like a lot of us – was looking forward to 2020, of course at that time we didn’t know 2020 was to be virtually written off. So, here’s to 2021 and look out for this KTM on the track.