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Desmohog

When your last project involved shoehorning an Alfa Romeo car engine into an aftermarket Harley frame, what do you do for your next one? Well, if your name’s Chris Barber and you’re responsible Crossbreed Cycles, you come up with an even more twisted idea – mating a Harley bottom end with a Ducati top end.

The spark for the idea came when Horst Heiler, a German motorcycle magazine editor who’d previously written a feature on the Alfa, sent Chris a picture of his own bike, which featured a Shovelhead cylinder head mated to an NSU motor.

Of course, Chris couldn’t simply copy this idea wholesale. Firstly, it had already been done and NSU motors are not exactly commonplace in the States where Chris was living at the time. Then again, Harley engine parts are as common as muck over there and cheap as you like on eBay, which is where Chris duly picked up a set of Evo crankcases.

Now, to build a hybrid motor around and onto said cases, Chris needed a top end, but from where? Well, having spent his youth riding, destroying and then rebuilding Fizzies before discovering cars and girls, when he returned to bikes, it was to the Ducati marque that he was drawn. The first one he owned was a 900SS, and fortunately he still had a set of heads knocking around in his garage somewhere. Problem solved. Hah! If it was that easy we’d all be building bastard love child engines, wouldn’t we?

The reason that Chris had been living in America was that he’s involved in the semi conductor industry. No, I don’t know what they’re used for either but apparently there’s a lot of money involved and mobile phone technology relies on them. Chris’ job out in the promised land was running the workshop that kept the machines in the semi conductor factory working smoothly to produce a steady flow of the things.

Being an enterprising sort of chap, Chris convinced his employers that his workshop really needed filling with state-of-the-art CNC machines, and that it would also be a very good idea to provide him with the very latest software package in order to operate all of this equipment. Not for one minute did it enter his head that it might also prove to be extremely useful when it came to his personal bike-building projects. Well, that’s what he told me, and who am I to disagree…?

It was strange then, that he would often find himself with the odd period of downtime in the workshop when the software wasn’t being used for anything and the CNC machines were idle. There was only one thing for it then, which was to put it all to work designing the one-off components required to marry his Italian cylinder heads to the American set of crankcases.

The first step was a set of barrels that would bolt to the Evo cases while, at the same time, allowing the heads to be bolted down. The resulting CAD drawing was then shipped off to Axtell, a company that specialises in that sort of thing. Now, just to prove that Chris might be talented but not infallible, he admits to making a mistake with the drawings and the barrels ended up an eighth of an inch too tall. Fortunate, then, that he found a set of over-length Carillo conrods on eBay going cheap… because they were too long for a regular motor. Job’s a good ‘un.

The next task was designing and machining up the blocks to hold the gears that take the toothed drive from the Harley’s camshaft and convert it to belt drive to suit the Ducati heads. Luckily, it was a quiet week in the office when Chris took that one on…

If I was clever enough to get that all figured out satisfactorily, I’d have been happy to call it a day and move on to finishing the bike but Chris isn’t just an engineer, he’s also an artisan. To him, something just didn’t look right. Well, that was until he got a second 900SS rear head and mounted it on the front pot after turning it through 180 degrees. Apparently, it works better visually as the cooling fins line up and it angles the Mikuni flatside carbs evenly on each side of the bike.

Just to prove that not everything on Desmohog, however, was high tech computer designed and machined – the carbon fiber velocity stacks the carbs are wearing were moulded on Pot Noodle pots and finished off with discs cut from kitchen sieves!

Given the work he’d put into the motor, you’d think it would be a simple job for Chris to match it to any gearbox that took his fancy. Well, it would have been, but when eBay threw up a cheap RevTech 4-speed Shovelhead-style ‘box stuffed with five gears and a kickstart, it would have been rude not to have bagged it, so he did. It also made it easy to bolt on a BDL primary belt drive set-up.

At this point in the build, things had to slow down due to an impending move back to the UK. However, before leaving the States, Chris popped over to Kustomwerks and scored one of the Kraftech rigid frames which it distributes and packed it up along with his belongings ready for the journey home. Shipping it amongst his furniture also helped to avoid getting hammered by HM Customs and Excise when he arrived back in Blighty.

One last piece Chris collected before he left the USA was the aluminium petrol tank. Another eBay find, its exact origins remain unknown, but he but he thinks that it’s an aftermarket tank from the ‘60s intended to fit a Brit bike.

Once Chris was reunited with his various boxes of bits down on the south coast, he started to throw it all together to get the Desmohog up and running as quickly as possible. Well, you’d waste no time either if you’d just done a deal for a Maserati car engine as the basis of your next project.

A few hours browsing the internet soon yielded a front end from an anonymous Jap dirt bike and a set of 17in Excell rims laced onto XL650 hubs that’d originally been destined for a supermoto project. Chris didn’t buy the wheels just because the price was right – he actually wanted them in that size. As he says, “Bobbers might look cool with 21in wheels but they’re a bugger to ride. So I’ve put sensible sized wheels on mine.”

The choice of 17-inch rims also opened up a whole range of available sports bike tyres to Chris, which fits in with his idea of building what he describes as a café bobber; a mix of traditional American Bobber and classic Brit café racer. All of which explains the styling of the seat hump. While he may have been keen to get the bike finished and on the road, he still took the time to create a virtual 3D model of the seat hump in CAD and then virtually slice it into 12mm-thick sections. He then transferred the dimensions form those slices to sections of MDF and glued them all together to create a buck from which he could take a mould. This was then covered with layers carbon fiber to create the seat hump.

The subframe that Chris constructed to hold said seat hump incorporates a stainless steel oil tank with integral filter, which he TIG-welded together when he was finishing off the Desmohog. And while he had the TIG gear out, he also knocked up his own rearsets and a top mount for the engine.

Now that the Desmohog is up and running, Chris is unsure what he ought to do with it; keep it as a run about, or sell it and crack on with his Maserti project. If he does hang on to it, there’s a chance that the Desmohog finds itself running a supercharger, to which it would be eminently suited thanks to its relatively low 9:1 compression ratio, though a slightly thicker base gasket would drop the ratio by just enough…

Then again, if someone wants to drop him a line at cjb@crossbreedcycles.co.uk, any reasonable offer would certainly be considered.

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