The end result Project Derbi You wouldn't believe how much drama this beastie has caused Brendon Part two of Project Derbi GP1 50 Open sees our Derbi achieve some pretty amazing results, we expected it to be quick but the end result surprised us, so did the controversy it created.
We did some testing with the GP1, filmed a couple of runs for proof , posted it on youtube & next thing you know it created a furour as LA class 50cc scooters are only allowed to do 50km/h to enable them to be ridden on a car license. Our one was filmed doing 111km/h which really upset a few. The majority of feedback was positive & whilst it isn't everyones cuppa tea most thought it was cool to see a 50 go that fast especially those who ride a 50 daily. To those who were upset & complained I suggest you find a sexual partner, you really need one...
Lets be perfectly clear on this one, our GP1 50 is a dedicated race scooter, it was never intended for street use. It's got racing numbers, our logo plastered all over it, it's loud & hard to live with on a day to day basis.
In order to get the liquid cooled 50cc Revolution engine really stonkin we started by replacing the standard exhaust system with a Gianelli Reverse which dramatically reduced weight & the restrictions imposed by Euro 3 emmission standards. with the exhaust flow dramatically improved it was time to work on the induction side, a 19mm Malossi Carb with manual choke was fitted and the standard airbox modified to improve flow, no "speed holes" were drilled in the airbox.
On the transmission side a Malossi variator was fitted as well as a belt drive and contra spring. The standard clutch was replaced by a Malossi Delta clutch to provide more tuning control in the drivetrain.
When we entered the GP1 in the 2007 Six hour scooter race it arrived at the shop a week before the race, the parts five days later & even then we didn't get everything we needed. At its race debut it wasn't right, open the throttle & it would rev hard producing good power, only problem was the lack of a suitable contra spring meant there was a second delay before the transmission would respond. This is why it came second in its class to our own Monza.
This time around we were armed with a swag of parts & plenty of time to try different combinations of roller weights, variators, rollers jets & clutch settings. With this the problems were quickly sorted. We gave the Derbi a run against our Monza which won the 50cc class at the 6 hour & set the lap record at the 07 Le Minz 24 hour there was no comparison, the Derbi simply disapeared. The only thing left to try was the MHR replica 70cc kit.
The 70 kit was quite a bit of fun. In one of its initial states of tune it was quite.... aggressive, no more nasty with a hint of kink. It did not want to potter around with gentle throttle, it would sort of burble along in that unique two stroke song, bwabababwa bwa bwap so you would give it a bit more throttle to get it revving cleanly & next thing you know it would scream at the top of its lungs hook up & just take off. If it was wet expect wheelspin, it didn't want to travel along at a steady throttle it just wanted to keep accellerating & really preferred it when you rung its neck. While it was a bucketload of fun we really wanted a better power delivery.
A few tweaks on he intake side & adjustments to the transmission particuarly the delta clutch saw the refinements we wanted. The fine tuning made the scoot significantly more tractible and more importantly faster & easier to ride fast.
With all the drama the Derbi has caused we ended up removing all the bits as we have effectively developed our kit for this engine which is used in a number of other scooters such as the new SR50R Aprilia. The GP1 Open is now completely standard, back to original restricted road going format and has settled down in a new home with a new family.
Hopefully it will relive the wild days again. But if it doesn't our GP1 50 Racing will be here soon & so will our ultimate 50cc build up ever.
Here is the vid that caused the drama's.
published 7/06/2008 |