A Single passion
Dave Newitt is a driven man; his desire to build the perfect thumper has to be admired as he gets it so right, so often. Chris Pearson samples yet another, but is it the final chapter? We hope not.
We love it whenever Dave gets in touch, it is always to inform that a new machine is nearing completion and would like to come and sample it. In this respect we has been lucky over the last few years, and for that we thank the man. There is something special about his ideas of what makes a great bike and the end result is always something that excites, and above all else, works in the real world; the only trouble is, his machines are that good I for one, usually end up hankering after one for a good while later, and on occasions have had my cheque book on standby ready to make a purchase.
For the latest creation, christened the Phase 4 Supermoto, great detail has gone into the Yamaha engine, lightening and tuning many components in pursuit of a high power output. A heavily machined, reworked, and its stroke shortened, SR500 crank now holds a lightweight Carillo rod and a JE piston, while further up 1mm oversize valves do their business in bronze guides, controlled by tungsten rockers and a specially designed and fabricated Newman race cam. The cam sits in an SR400 rocker cover, the baby, Japanese market only, SR went on to be developed further by Yamaha and, as such, utilises improved oil ways with overhead spray bars, and a more secure method of holding the rocker arms in place. In the bottom end, with its magnesium casings, the clutch has been beefed up by using an over sized SR500 basket, helping to handle the sizeable increase in power, as it makes its way to the rear wheel.
Considerable head work has been done to get the compression up, from the lowly 9:1 that Yamaha decided was needed, to a whopping 13:1, this has seen a noticeable increase in power and torque, with around a third extra in all departments at the present time, but this figure is set to rise with further development work. Dave admits there is a lot more to come as the programmable ignition has, to date, proved a complex beast, and once he has fully mastered the complex curve that this engine clearly requires, then one can only guess at the power to be had. The engine breathes through a home built exhaust system, with an open 38mm Mikuni sat opposite, throwing in great handfuls of mixture with every inlet stroke, the sound it makes is quite unique being akin to an old open mega Brit single, but with an added urgency. For the chassis its pretty standard Dave Newitt fare, a Yamaha TT500 frame, now with extra gusseting in the key areas, holds a set of CCM upside down front forks and yokes in place, with a home built swing arm, adding 10mm to the wheelbase in an attempt at damping down the mad wheelies that the previous machines pulled at every opportunity. The CCM fork legs have been shortened so the head geometry remains true to the original XT without four inches or so of extra fork outer sticking out of the to yolk, meaning the bars can stay pretty much where they used to be too, and it all runs on modern rubber, Maxxis Excel radials doing a cracking job of keeping the whole plot going in something like the right direction.
The original looks have remained, there can be no mistaking what machine this started off as, but everywhere you look there has been worthwhile changes. The attention to detail is impressive, custom made clocks from Speedhut in Utah, add the finishing touches to the cosmetics, each one backlit to match the paint scheme, the tacho even has a programmable rev limiter. All the usual warning and neutral lights are now set into the bars, a little low down when compared to other road machines, but effectively keeping the console area neat and clutter free, but still doing their job well. At the rear end an LED tail light teams up with a set of mini indicators to keep the lines smooth, and speedy looking, an image aided no end buy the striking orange XT style paint job.
Starting this fire-breathing machine is an art, no time for pussyfooting around, just get the engine slightly over compression using the de-compressor, and give it all you have. If you get it right, the engine literally explodes into life, get it wrong and it feels like your right foot has instead. The engine quickly settles into a booming tick over, just like a standard XT, and not at all hinting at what is about to take place. Add a gear into the equation and you are ready to rock, the clutch is smooth and easy to operate, the throttle is light too, arguably too much so, and every input yields a far greater response below decks in the engine room.
The way this lightened and tuned engine produces its power is more akin to a two-stroke than a thumping 70s single-pot diesel. The revs rise and fall in the blink of an eye and it’s a hard job throwing the gears in to the equation when accelerating to keep ahead of the engines hunger for more, especially as every gear added means there is more for the brain to keep pace of.
Once settled in on this hotted up XT, a few things become apparent, it is very well balanced, with exactly the same weight placed on each wheel, and supremely powerful too, these two attributes working perfectly together to create a ride brimming with adrenalin. Each and every turn of the twist grip yields even more go, the front wheel is light until 4th gear is well home and fully airborne throughout the lower two gears. The extra swing arm length doesn’t help one little bit when it comes to keeping the front wheel communicating with terra firma, it would if the power hadn’t been increased to such an extent but you cant have everything, so it’s a case of learn to wheelie or ride something else. The more modern chassis enhancements mean the bike is rock steady under braking, as it is when cranked over, to be fair, the original XT handled surprisingly well on the road, but this is light years ahead of that benchmark and would be in its heaven, and virtually unbeatable too, on a large kart track or tight short circuit.
Dave calls this the ultimate in XT development. He implies that there will be no more, and that this is the final chapter in his efforts to create the perfect big single, for now we guess he is right, but we’ve known Dave a long time and it wont be too long before his mind starts racing again. Give the mag a shout when you have Phase 5 finished, and we’ll be there.
Buying an XT
Want to build one for yourself, well first of all a donor machine is needed, but what do you need to look for to keep costs down. Well if the original body parts are not needed then aim for something cosmetically not quite right, but if parts are missing, and you want to keep the original look of the XT, then this is where costs can start to rise. Keep a good look out for frame damage, three areas stand out as needing a keen eye when buying, the rear frame rails should follow the line of the seat perfectly when viewed from the side, if they don’t then it is likely that the bike has been flipped, and the tubes bent. Next up is the headstock; any sign of oil weeping around this area suggests that the front end has been twisted and the welds that join integral oil tank to the frame are cracked.
Check too that the footrest are mounted on their original spines, particularly on the kick start side, these do wear and the temptation is to weld them in place, but this makes getting the engine out of the chassis impossible without removing the weld and starting again, a proper repair is nigh on impossible so avoid a bike with this complaint. The side stand can become sloppy, most people can only start the bike when on its stand, as it is a job that requires considerable commitment, this places huge strains on the stand which in turn starts to wear, if the play is due to the frame mount having become worn, then again, it can be tricky to remedy.
The engine should be a good starter, certainly, within a couple of tries, it should be bursting into life, with no smoke from the exhaust and little in the way of top end noise either. The bottom end is a tough cookie thanks to the extensive use of hefty roller bearings throughout, this, allied to the standard engines relatively low output, means there is few common faults in this department.
For more advice and help on XT500s check out www.yamaha-xt500.com
An owners tale
The creator of this and many similar machines, Dave Newitt, is well known to most XT owners the world over, simply type in XT500 into any search engine and his many websites and forums will be in the top ten every time, such is his notoriety on the subject. His workmanship is now legendary and recently he turned to restorations on a full time basis, moving to new premises in his hometown of Hinckley. The move giving him over a 1000sq feet of space to move about in, and has invested heavily in facilities since then, Dave now has MOT test status and has added a large ultrasonic cleaner to aid in his stunning restoration work.
His desire to build the ultimate XT appears to know no bounds and the machine seen here his is 4th attempt, all having been cracking machines in their own right, (I tested the first one in October 2005) with each version taking the ethos that next stage. Dave says “ This is the final incarnation but, to be honest, I have stated that with the others too”. This time around, and having sorted a successful formula for the chassis design long since, Dave has concentrated on the power plant “I was aiming for 60bhp” Dave adds “and despite many problems, I am getting nearer with very dyno run. I dare not add up the cost of all this development and the parts it consumes, at the end of the day it’s all done mainly for fun, and because its there to be done. Next time I will build a bike with fuel injection as after working closely with the manufacturers, the Power Dynamo digital ignition now provides enough power to run this too.”
So there is going to be a next time then?
Specifications Yamaha XT500 Supermoto Phase 4
Engine air-cooled single cylinder four stroke SOHC
Bore & stroke 90 x 83.5mm
Compression Ratio 13 :1
Carburetion 38mm Mikuni VM
Max Power 50bhp @ 7250rpm
Torque 36ft-lb @ 5000rpm
Ignition Power Dynamo digital, 16 programmable curves
Transmission 5-speed, wet clutch, chain final drive
Frame steel cradle
Suspension 48mm USD telescopic forks
Twin rear shocks oil damped
Wheels 120/70 x17 160/60 x 17 Maxxis Excel Radials
Brakes 330mm disc Brembo two-piston floating-caliper
220mm disc Brembo single-piston floating-caliper
Fuel capacity 8.8litres
Top speed 100mph
Tel 01455 246368
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