www.jbsracing.co.uk

Twin Spark Head – As the bore of an engine goes up the distance that the flame-front has to travel after ignition obviously increases as well. There comes a point when 2 sparkplugs igniting the mixture at 2 separate points begins to show a significant benefit. A bore of 105mm or indeed 108mm is beginning to approach this point.

JBS Racing experimented with a twin-spark Husaberg head back in 2004. The system that we were using then retained the OEM ignition. It generated the second spark by using the output of the lighting coil to power a DC-to-DC high voltage generator, this charged the capacitor in a conventional CDI. The trigger was the hard part, it needed to be perfectly in sink with the OEM firing. To do this we wrapped a lead around the OEM HT lead this acted as a capacitive sensor I.e. like those used for dyno RPM measurement at the HT lead, the output from this was amplified and used to trigger the second CDI piggy-back style.

The second plug is installed on the magneto-side of the head as it would sit on the cases to the right and between the inlet and exhaust valves on that side. The procedure is simply to bore a hole in the head and weld in a slug that is then drilled and tapped. The water jacket is not blocked and in fact water flows around all sides of the newly installed plug holder keeping it nice and cool. The valve seats have to be replaced with this mod so it is good to do when time comes to replace the seats anyway.

The 2004 JBS Racing system worked but was complicated, the bike looked like a telephone exchange with wires everywhere and it was expensive as it was all custom made electronics.

Now in April 2008 JBS Racing are again experimenting with our twin-spark head but this time fully replacing the OEM ignition system. A new rotor, stator, CDI and twin-HT coil is provided. The whole system costs less than an OEM stator. No lights can be provided with this system unfortunately. The system is being tested for durability now and will on sale along with the required machining work pending the results.

This entry was posted on Wednesday, April 30th, 2008 at 10:20 pm and is filed under Engine Develoment. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.