95Racer Development

After summer full of interesting bike projects, we finally found some time to give the latest engine specification a good run out. For this occasion, we were very fortunate in having Toby Markham offer his time to evaluate our little project.

We’ve been talking to Toby for several months and everyone’s diaries finally lined up for October 12th. Toby has been riding a privateer Aprilia in the European rounds of the World 250cc MotoGP Championship. Toby was by far the most capable rider we’ve had on the bike to date. And, the first one to bring the much desired 250cc 2-stroke perspective. Afterall, our 95Racer was designed to compete with the 250cc class.

The engine now makes slightly less peak power at 92 bhp at the rear wheel but a significantly improved torque curve. It also hangs onto power longer. The exhaust system still needs more work and this will happen over the winter months. However, we felt it was worth testing before the end of the year, especially given Toby’s availability now.

So, we set off to Cadwell Park in Lincolnshire, England for a day of testing. We even managed to get a beautifully sunny day, which is not the norm at Cadwell Park at the best of times!

During a track day at Cadwell Park last September, Gary Inman of Performance Bike Magazine arranged for their photographer to take a few pictures, which Gary turned into a 3 page article now published in their February issue. It’s at your newstand now! I especially like the 3/4 frontal view.

Life’s been pretty hectic: new job, family expanding, etc. So, my apologies for the lack of updates. Unfortunately, I can’t promise that the frequency of updates will improve but I’ll definitely try to do better.

Anyway, I didn’t get to race this year at all, again due to time constraints and also a certain engine tuner letting me down very badly. In hindsight, I should have pulled the plug on him at the beginning of the 2008 season.

The bike has continued its development. I was able to improve both on reducing the weight further and increase horsepower. The weight reduction has come from some chassis changes, but mainly on the engine. So, the engine work has paid off on both fronts. The other increase in performance, again weight and power, has come from exhaust development work. Plus, it now easily meets the 105 dB race noise limit.

The latest news is that Performance Bike magazine will feature the bike (presumably next month). The bike was scheduled to be tested by Guy Martin at Cadwell Park on the same day, but unfortunately we had an oil seal let go and couldn’t fix it on the day.

Here is what the bike looks today:

Just in time for Christmas, we finished our own special Christmas surprise. Feast your eyes on our 95Racer in its full glory. Well, that’s glory at least in our eyes.

2007 was very much a year of development mainly focused on getting the most from the engine. This also required a complete redesign of the airbox system as the stock one is woefully inadequate as you pursue serious gains in horsepower. Some related work then provided further opportunities to reduce weight.

The initial goal and the reason for the 95 moniker was to get 95 rear wheel horsepower in a 250cc GP sized, 4-stroke engined motorcycle weighing 95kg has very nearly been accomplished. Unsurprisingly perhaps, everything hinges around the engine. We are now only a couple horsepower short of our goal and are confident that we can at least reach it by spring 2008. The weight goal is still a little further off and the obstacle is again the engine. Much work has gone into lightening it (and everything else) but it is still overweight in our view. We are not too far off the 95 kg but further reduction will get seriously expensive. It is likely that the weight will largely remain as is for at least 2008. Still, the performance of the 95Racer is already pretty spectacular and we don’t this as a serious limitation.

Now, without further ado, here are a few of our favourite pictures. Let us know what you think. All pictures are courtesy of Cope Images, www.copeimages.com

One of the items we identified pretty early on was that we wanted to shorten the left side of the engine. This is where the starter gears, flywheel, and generator live. To save weight, we wanted to eliminate the starter and its associated gears and so went a little bit further.

The tuned engine now has a shorter crank with a new, one-off flywheel and a light weight generator. This allowed us to shorten the left side engine cover considerably. You can see the difference in the following picture with the stock one on the right.

Here is a picture with the new flywheel installed on the shortened crank. The remaining flywheel mass is now located much closer to the centre of the engine.

The hole in the middle of the modified cover is for access with the external starter.

The next set of pictures show the difference between the stock flwheel and the replacement we are now using. It has about a third of the inertia and also weighs a lot less. We also make one that has even less inertia but it makes the engine less happy.

So from left to right:

• This is the lightest version of the flywheels we’ve tried so far. It has probably just slightly too little inertia, although it may work well at certain tracks. We will track test it in 2008 more thoroughly. The black band around the centre are the new rotor magnets imbedded in carbon fibre epoxy. It has just under a quarter of the inertia compared to the stock one.
• This is a modified stock version which has the recess for the sprague clutch machined off. It is 600 grams lighter and has 70% of the inertia compared to the stock one.
• The left most one is the stock one. It weighs 2.2 kg and has an inertia of 3.25 kg.dm2. The starter gear and sprague clutch has been removed in this shot.

You can also see the difference in the generator stator. The replacement produces about 200W which is still plenty to keep the battery topped up and run the ECU, fuel injection, fuel pump, and dash logger.

Eliminating the starter system and running a smaller generator also allows us to run a much smaller battery. The picture below shows the 3 different batteries that we’ve used.

From right to left:

• stock battery, 4140 g wet weight
• what we used last year, still running an on-board starter and standard generator, 2660 g
• what we are using now with the light weight generator and no on-board starter, 890 g

That means just in battery weight we saved over 3 kg. Quite a difference! All in pursuit of more power and lighter weight.