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Bigger and Bigger – Now that the “700” kit is working well JBS Racing are again focusing effort on our 86.0mm stroke crank. This along with the 108.0mm piston allows us to make various configurations from 735cc all the way up to 790cc. Several engines are being tested now running various cranks and pistons with capacities over 735cc. Results will be posted soon. For the latest email ben.ballard@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.

Steel Bearing Liners – The original Husaberg crank main bearings are really undersize even for the “650” engine. They have proved problematical in every application that the Husaberg engine has been put to be it the high revs of Supermoto or the high loads of Sidecar.

JBS Racing was the first tuning company to use 20mm wide bearings in place of the 16mm wide OEM bearings. Initially we ran a 20mm wide roller on the drive-side and a 16mm wide roller on the magneto-side, this was easy without a counter-balancer as there was room for the 20mm bearing to sit in the original housing.

As mentioned in a previous post we decided that to achieve the smoothest engine that we could we would re-install the counter-balancer. This means that the original bearing bore in the case must be machined 4mm deeper to allow the 20mm wide bearing in without impinging on the space that the counter-balancer swings in.

As we had decided that we would set the cases up on a machine and bore the drive-side it seemed just as well to do both sides of the engine and run the 20mm wide bearing in both sides. The only problem with making the bores deeper is that the seals msut then be move out by the same amount that the bores have been deepened, 4mm. To do this we welded aluminium rings to the cases and machined a very small amount off of the back of the magneto rotor. This system works very well, but the bearing is only retained by a press-fit into the cases. Our ultimate goal on the crank main bearings was to fully retain the bearings in the cases and fully retain the crank in the bearing thus eliminating any movement and sources of damaging vibration and hammering. Many Japanese bikes have fully retained bearing and crank systems by design.

Eventually JBS Racing had enough time to design and machine steel bearing liners. The cases are bolted together line-bored, with ensures that the bearings in both sides are in perfect alignment, then the steel liner and pressed in and screwed to the cases. This system has 4 major benefits 1) The bearing bores are permanently lined with heat-treated steel so re-builds do not ware the cases 2) The bearings and crank are fully mechanically retained, not relaying on a press fit 3) The bearings are in perfect alignment 4) They are not compressed by the OEM over-tight press-fit which reduces the “C” clearance in the bearing by about 2 numbers in our experience.

Stuart Brown Husaberg – Team Brown tried a Husaberg NOT supplied by JBS Racing in the winter of 07/08 with limited success. A main bearing modification that works well in Supermoto was installed by the supplier but it failed very quickly with the added stresses of Sidecar.

JBS Racing suggested a bearing modification similar to the one that we fit and supplied some bearings for it. The engine lasted much better with these bearings. The cases had been cracked by the failures prior to fitting the JBS Racing bearings and ultimately they failed.

We are now building a JBS Racing supplied Husaberg for testing.

JBS Racing Camshaft  - The head on the Husaberg is a generic casting that is used for all the capacity engines that Husaberg make or have made. These range from a 380cc up to a 644cc the head is really struggling to supply enough fuel / air mixture to the combustion chamber once you take the engine beyond “650”. This leads to engines that have a lot of power at the bottom of the rev-range but no more or even less than stock at the top depending on how big you take the capacity. The engine feels a bit like a tractor.

The solution to the problem ultimately is to make a bigger head casting with bigger valves and bigger gas passages. This is not economical for the Husaberg at present (we have looked into it) so the next best thing that we can do is to look at the camshaft.

It is normally difficult to increase the lift and duration of a camshaft without having adverse affects on the life of the valve train. However the Husaberg camshaft uses cams with a large negative radius / hollow flanks. This is so that they can achieve a relatively high-lift with a short duration. This design has the very undesirable effect of producing very high peak accelerations (twice what is considered “normal” from a design point of view). So it was possible by careful design to make a camshaft that gives both an increase in lift and duration but at the same time reduces valve train forces so promoting better life.

As we had decided to take the plunge and have a batch of camshafts made we also decided that we would try out an idea we had for an adjustable camshaft. So the design below was produced by our machinshop. This design allows interchangeable lobes to be put on the camshaft. Replacement lobes and even custom lobes for a specific engine application are cheap as the main part of the camshaft is retained in each case.

Using this camshaft fitted with an appropriate profile for the capacity that is being run all JBS Racing engine configurations can be optimised for smooth power all through the rev-range including the top-end. This camshaft will also fit KTM with a small modification contact us about it.

Gaskets – It was not possible to use an OEM head gasket with the JBS Racing “750” or “700” kits. The deck height on the Husaberg engine is almost zero so if a head gasket is used that has a smaller bore than the piston being run the piston will hit the rolled steel lip of the gasket. This is the case weather you are running a JBS Racing 105 / 108mm piston or another kit such as one running a 103mm piston.

Initially we were using Aluminium or Copper soft-metal gaskets as these were relatively cheap to produce and did not require the high tooling costs of custom gaskets.

Our method of sealing required very flat heads and cases, excruciating cleanliness and meticulous assembly. It worked Ok but only if all these things were done right. So we decided that we need to have an OEM style fibre gasket made to make the engine easier for the average racer to put together. We now have custom made JBS Racing fibre head gaskets available in 105mm & 108mm bore. At the same time we decided that we would have after-market gaskets made by our supplier for every other gasket on the Husaberg engine, these are also available from JBS Racing for less than OEM parts.

“700” Kit – We refer to kits using the 105mm piston and OEM crank shafts as “700” kits. In fact it depends on the model of crank you use of course as to what cubic capacity you actually get. A 2000-2003 crank if it has an 82mm stroke will produce a 710cc engine, a 2004-2008 crank if it has an 80mm stroke will produce a 693cc engine.

We have run both engines for many hours. The 693 is more reliable than the 710 for 2 obvious reasons 1) The capacity and hence power is lower so the parts are less stressed 2) The pin on the 80mm cranks is 35mm up from 32mm on the 82mm stroke cranks and so is much more resistant to flexing. Both engines are as reliable as their stock equivalents in our experience in Sidecar.

Generally speaking the “700” engines are very reliable. They last as long as at “650” in the same application. I.e. if you are getting 100 hours out of your road-registered “650” supermoto engine or more you will get 100 hours or more out of the “700”. If you are blowing up “650” engines every week-end in a Sidecar the same will happen with a “700” kit. It won’t be any worse but it won’t be any better. There are other modifications that greatly improve the reliability of the engine especially when you are using it in a Sidecar. These are 1) Main bearing mod (Details will be provided in a later post) 2) Camshaft 3) Oil cooler

Titanium pins - As part of our weight reduction exercise on the piston kit as a whole we also looked at the wrist-pin. JBS Racing made some prototype Titanium pins and worked with Burnel

Diamond-Like-Carbon is a space-age coating technology that is used in F1 and MotoGP engines.

The Titanium wrist-pins are less than half the weight of their steel equivalents. However we are using Steel wrist pins for most customers and they seem to be working well, Titanium does give a performance improvement but is expensive and not necessary in most cases. These Titanium pins will also fit the KTM engine.

The first component that we decided to put on a diet was the piston. We had been using an off-the-shelf piston that we were able to modify to fit the 750 kit but this gave us a few problems. The piston was heavier than we wanted it to be, the compression height meant that we had to run a packer and it could only be used with our JBS Racing conrod and crank.

We decided at the design stage for the new piston that we would make it compatible with the OEM Husaberg piston. So the JBS Racing 105mm piston is now exactly the same as the 2006 OEM Husaberg “650” 100mm piston except for the bore size. It is the same weight, compression height, valve pocket depths and angle are the same etc.

This provides us with a light piston that can be used in the 750 and our newer experimental engines and is compatible with the OEM crank-shaft and conrod allowing us to make a “700” kit using an OEM crank if the customer does not want to run an 86.0mm stroke.

We also had 108mm piston made at the same time, again these are fully compatible with the OEM piston only the bore is different. This allows us to make the following configurations –

We ran the original 750 kit with out a counter-balancer in the crank but weighted to the correct balance factor for a counter-balncerless system. The engine was smooth and didn’t seem to need a counter-balancer in this configuration. However once we had added the weight to the big-end pin, piston and conrod the whole dynamics changed and we began to see bad vibration in some chassis but none in others.

We tried all sorts of balance factors, this is often necessary anyway when you alter a single-cylinder engine and is only able to be empirically derived in most cases. After many trials and finally a cracked engine mount we decided we would have to loose some weight from the components to get it to work and re-install the counter-balbacer.