Gas Gas bit on the side!
By TMX Archives on 15th Nov 07
LAST week the tiny, Gerona-based Spanish Gas Gas factory made page 3 with their exciting, new-look Raga two-stroke model this week they are back, with a sensational prototype fuel-injected four-stroke trials model powered by an all-new side-valve engine!
The prototype, which has been tested by no less aperson than seven times World Trials Champion Jordi Tarres, made itsworld debut at the Milan motorcycle show last week where it became amust-see exhibit.
The side-valve principle has not been used in motorcycle design for many years although it is popular for industrial use mainly because, compared to OHV or OHC designs, it is simpler and much cheaper to produce.
The side-valve (or flat-head) has several pointsin its favour: it is cheap to produce, it is comparatively light and particularly important for a trials engine offers a considerableadvantage in engine height in fact it is no taller than a comparabletwo-stroke. This means the centre of gravity is kept much lower and itfrees up much-needed space for auxiliaries
The down-side is that the side-valve arrangementmeans it is very difficult to incorporate an efficient combustionchamber shape as the two valves sit alongside the cylinder. However, byemploying electronic fuel injection, Gas Gas is clearly aiming atgiving themselves the best chance possible of efficient, cleancombustion. Side-valve engines traditionally have a natural reluctanceto rev but they do churn out excellent low and mid-range power. But GasGas claim that their new baby actual capacity not known at this stage revs to an impressive 10,500rpm. Coupled to this impressive figure,the complete machine weighs-in at just 2kg heavier than their currenttwo-stroke and overall performance should be promising.
The engine sits in a traditional Gas Gas perimeterchassis with the exhaust almost circumnavigating the barrel beforeexiting into a standard shaped GG silencer.
Viewed from the left side, the machine could be aconventional two-stroke. All the action is on the right-hand side ofthe motor with the valves, water-pump etc and the exhaust-port doeslook vulnerable.
This is a prototype however, and dressed-up in GasGas red and white it does look good. British importer John Shirt hopesto bring the four-stroke over to display at the Dirt Bike Show whichruns from December6-9.
And the final news, when the four-stroke does hitproduction September next year as a 2009 model it is not expectedto be priced much higher than the already competitive two-strokeGassers.