MC28 NSR300SP

MC28 NSR300SP

April 2009

This project has been the longest running project in the history of TYGA Performance and never seems to be finished but maybe it is time for an update.

I originally bought this SP version of the MC28 in 1995 as a replacement for my first NSR250 which was a 1990 MC21'R'. It had just arrived from Japan as an accident damaged bike and repainted in Rothmans. Compared to the MC21, it felt more substantial but also heavier and slower. It was very torquey for a 250 and I particularly remember Matt and I slow speed cruising, two up, around Lopburi looking for some dubious nightlife on a Saturday before his race. The bike performed well at this task and not at all like the two stroke racer it was derived from. However, on the flip side, it could actually get beaten in the night time Ratchada Road traffic light drag race by a mere Kawasaki KR150 which was a bit embarrassing given the extra cc, the lofty price tag, and all that PGM technology. 

Luckily Matt was a professional racer for Team Colin Marshall Racing and happened to be racing MC28s at the time. Colin quickly sorted me out a set of OEM SE bodywork in mint condition and a set of race pipes with Matt setting the bike up on the dyno as part of the deal. The power went from the usual mid 30s up to around 55 which I was happy with given the stock card and general stock spec of the bike. Little did I know that about 5 years later Matt and I would go into business as TYGA Performance and NSR250s would be our core model; or that I'd keep this particular bike for another 14 years. I'd never have guessed that it would look and perform the way it does now. 

So what has been changed? As far as I can figure, everything except the frame which is still the original. Apart from the Rothman's and the SE scheme, it was transformed to a red and silver scheme (inspired by the 1998 launch of the MV Augusta) followed by a 2000 Rossi scheme.

I eventually settled on the 2004 Pedrossa. Winning the championship in his first year on a Honda made this race replica the obvious choice. The paint is starting to get a bit tired now so it may be ready for a change soon. The bodywork may have remained, but underneath big changes have taken place. I'll let Matt describe what he has done to the engine: 

 

"Many moons ago, I'd already breathed a bit of life into Paul's MC28 250cc motor, but eventually he saw the light and wanted a 300cc. He ran this for a while in 'stock' form and life was good. However, Performance by name means performance by nature, so out came the engine for a bit more surgery.

It stayed as a 300cc, but I spent a few hours on the cases with some epoxy here and some grinding there to assist flow and pumping efficiency. All the 'dead' space in the cases, such as the oil drain pockets and behind the reed valves is filled, and then re-contoured.

The mixture is fed into the cases through modified (bored and polished)  HRC kitted MC28 carbs, and controlled by TYGA Hi-Flo reed valves fitted with HRC RS125 'A' kit carbon reeds. Foam filters keep out the small children when it is on full volume.

The cylinders were stock, so another couple of days saw their transformation with completely new port timing, time area and angles. Wiseco pistons replaced the stock items. These US made slugs are lighter and stronger than the stock pistons, so it lets the engine rev faster and harder. The big bang is controlled by the very efficient VHM heads, which are designed for a tighter squish clearance and a chamber more biased to the top of the rev range. The mixture is ignited by RS250 plugs and caps.

A lightened MC28 flywheel is fitted to further assist in engine acceleration.

The gearbox has also had some treatment. The primary drive and driven gears are lightened, as is the clutch hub and basket. The transmission plate is modified to fit an extra needle bearing for the shifter shaft  to enable smooth and silky gear changes. The clutch itself is beefed up with out TYGA dry clutch rebuild kit.

Setting up the carbs on the jungle roads near my house is a little tricky, but the locals love it......probably.....and I've totally lost count of how many people ask me if my fuel's run out, or the spark plug fouled as I push home after another plug chop :-) "

Cooling is taken care of by an F3 radiator which is basically an RS250 radiator specially made by HRC to fit the NSR250. The water pump housing is a special big bore HRC item as is the overflow bottle. The top of the radiator has the HRC shrouds for the air box and ram air is an option later, though hardly required because the bike is rarely at high speed and has plenty of power as it is. 

   

The chambers are made to the normal TYGA specification from stainless but have a special 'Spectrum' titanium coating. These are an experimental set but if there are no technical issues and the response for their looks is favourable, we will put them into production. First impressions are good, the finish is incredibly hard and should hold up well against chips and scratches. The chambers are bolted up to a pair of TYGA carbon silencers. Step kit is also TYGA and uses the optional master cylinder carbon heel guard. The master cylinder is linked to an HRC reservoir kit. 

The chassis of the bike now sports an NX5 front end complete with Brembo rotors and calipers. The front master is a Nissin radial and lines are all braided. There is an Ohlins steering damper to calm things down and handlebars are TZR250 3XV which I found to be lightweight and reasonably radical but less so than the stock NX5 ones. The frame is stock but the rear swing arm is an unobtanium HRC one that we were lucky enough to be offered. Rear brake rotor is skimmed down for lightweight but otherwise the rear brake system is stock. Wheels are BST carbon with the front being a 3.5 inch and the rear a whopping 5.5 inch. Previously, an NX5 5.25 inch wheel lived there without much drama albeit tight clearances. The BST wheel required spacing of the hub to the right and offsetting of the swing arm to the left to compensate. HRC rear Sprocket was relocated on the swing arm hub to keep in the original alignment with the front sprocket. Hub spacer and nut were turned down to allow for use of the R clip and the all important but often misplaced and missing black plastic cap! Rear suspension is a rare NSR250 Ohlins unit. I was lucky to get the opportunity to buy a bike with a blown engine and the shock fitted. So the shock found a better home on my MC28... 

The subframe and battery box are TYGA  and designed to mount the GP seat cowling. This reduces the overall weight by quite a few kg. The undertray is a hand cut flat sheet of carbon, (maybe a TYGA product for the future). Weight is further reduced by substitution of the steel meter, coil, upper and fairing stays with TYGA aluminium ones. The top triple nut is billet aluminium and the front wheel spacers aluminium too and with no mirrors or rear indicators, drag and weight are reduced further. I'm now looking at the sidestand for a future weight saving. Matt says I should go to the gym but that is another story... 

To me the signature features of the MC28 are the swing arm, the fuel tank and the key card ignition. These are all retained for sentimental reasons more than functionality. The ignition in particular would have been a lot easier if it had been substituted for the PGM III or even PGM II like Matt's bike  used to have  and most RS250s have but I wanted to keep this feature. I love the LCD display (the MC28 was the first mainstream production model to have one I think) and the card system never ceases to amaze people even today. The card in use is the HRC-030 unleaded one with a wire splice for street functionality. The bike lacks a speedometer but it hasn't really been an issue as the general rule of the road round here is drive as fast as you dare. 

Performance is very lively. The combination of lightweight wheels and a tuned 300 engine make for a bike which wants to lift the front end at every opportunity. Changes of direction are made almost too quickly and for anyone used to a bigger bike, they will need to adjust to the quicker response and discover the limits of how hard and how late a corner can be entered. The motor, being a 300, has more torque than the tuned 250 that it used to have. Riding in town or filtering through traffic is easy with power from just above tickover to the redline. Of course, the bike prefers to be kept in the upper reaches of the tacho but the low speed stealth mode comes in handy when not wishing to attract unwanted attention. Let's face it, that these days, not everyone appreciates the sound and smell of a two stroke on full bore. 

So what else is there left to do? Well there is always something to change and only today I decided I'd like to have a set of our billet triple clamps to replace the cast RS250 ones. Ram air, or at least carbon shrouding and airbox would be nice to keep the airflow clean and the worst of the grit away from the air filters. Other than that, I think this might be a project bike which is almost reached its completion. 15 years on and I finally have a bike I am satisfied with.. almost! (.....I don't believe that for a minute!.....Matt.)