The story of Bob

As a lifelong Triumph fan and ex racer of early 70s 250cc and 500cc Triumphs I’ve always admired, almost worshiped, the Rob North framed 750cc 3 cylinder racers. I was lucky enough to ride one at Mallory Park many years ago and was delighted that the reality was up to the legend. Attempts, years later, to wrestle that very same bike from it’s owner to restore and ride were not successful and the prices have leapt right out of my range recently so it was unlikely that I would ever have one all of my own. However…

Christmas 2010 finds my dear friend Stuart and my wonderful wife Sophie conspiring to get me a very special present. A frame advertised in Classic Racer magazine is claimed to be a genuine Rob North frame for a Triumph 500cc twin. Talking to the vendor convinces me that it is probably the real thing and at a price less than a modern replica a deal is done and I am a very happy boy.

Before the frame and swinging arm had even arrived Stuart and I had begun some serious research including contacting the author of a recent book on Triumph 500 racers, Claudio Sintich, who was able to quiz Percy Tait. Stuart talked to Les Harris of the 70sTriumph race shop and found the contact details of the man himself, Rob North. We eventually had a tale of 2 frames , the first of which was cut up due to wayward handling and another which had left no trace until now .

 

It is likely that the 500 Rob North project was abandoned as it became clear that the future for the Triumph race effort was going to be built around the new 750cc triple engine of the Trident. With no photos to go on I decided to build a bike inspired by the late works 500s and the early 750s amalgamating the most interesting elements of both.

 

The wonderful eBay was soon providing items of old bike loveliness for me to drool over. A period AP brake calliper for the rear disc would complement the double sided T.L.S in the front. This unusual arrangement was present on the factory Triumphs of the late 60s and I liked it’s quirkiness. I soon had a pair of wheels laced up with ally rims.

Still with no actual proof of the frame’s origin I contacted Les Whitstone who now manufactures the Rob North racers and arranged to take the frame up to their works for an inspection. This resulted in a wonderful morning spent with Mick Pearce who is the craftsman responsible for fabricating around 600 frames and relevant fixtures and fittings on the original jigs for getting on for 40 years.

As a result of my master class in R.N. frames with Mick during which my frame was minutely examined and offered up to various jigs I left with many small components to help me in my project, an order in place for an oil tank and some fork yokes and most thrilling of all, Mick’s confirmation that it was indeed a genuine Rob North frame.

My smile was so big there was a possibility the top of my head could break off.

The final piece in the verification process came when a contact made by Stuart on an internet forum was able to take photos of my frame to Rob which enabled me to phone him in California to discuss its origin.

“Yes I made it but don’t ask me who for, It’s a long time ago” he said. Not only had I talked to the man himself but he had confirmed that I have a genuine and possibly unique frame. The phrase “Dog with two Dicks” springs to mind.

I was curious as to why the main tubes on North frames do not cross at the steering head Norton Featherbed style as this was copied by everyone including Honda and this seemed the perfect opportunity to find out. Rob told me that before he made frames, he spent years repairing them and often this would include welding up and reinforcing Norton frames which had cracked in this area so when he began designing his own frames he was careful to avoid the problem. Simples.

I had to let him go eventually but what a great bloke to talk to. I promised to send him a picture of the finished bike which I’m about to do.

Because my frame is about 5” narrower than the triple frames I needed a bespoke ally petrol tank and there’s nowhere better for that than Nick Parravani’s Competition Fabrication here in Norfolk. Whilst there they also made the 2 into 1 exhaust to the dimensions in the Stan Shenton Triumph tuning book, added the missing oil tank mount and attached other missing brackets and fittings.

I didn’t see the evolving bike which had now acquired the name of “Bob” (like “Rob” but different) for a while as I spent several weeks in hospital having become suddenly rather ill. On escape from Hospital  the work was complete and a good friend, Dru, helped a rather wobbly but very excited me pick it up. It looked like a bike!

I was able to build up the bottom end of the engine, a ‘68 Daytona. And install it in the newly powder coated frame before going back into hospital for a bit of a valve overhaul myself. This was so there would be no lifting involved when I began the final assembly during my convalescence. Didn’t really want my giblets popping out through my chest.

The bottom end of the engine had been repatriated from the USA and had been badly neglected. The cases are a weird one-year-only design with un-used bosses for oilways unlike any other but I like oddities. The crankshaft sludge trap was solid and took hours to clean but the journals were surprisingly good so standard big end shells and timing side bush were used with standard late type conrods. All other bearings including those in the gearbox were replaced and a close ratio 4 speed cluster from George Hopwood was installed.

Whilst picking up the engine I was able to buy a good cylinder head from Clive in Coventry who had more Triumph bits than I had ever seen in one garage, and a primary cover which turned out to be the wrong one but actually ended up being better, as I had to do some modifications to get the Electrex World ignition in.

Off work but unable to do much I had a local engineer, Paul Purple, who had already pressed in the new main bush, shorten and re-thread the fork legs and modify a  3/8” front sprocket to take a ¼” chain to match the selection of rear sprockets purchased at Stafford. These fitted a carrier I turned to suit the T140 rear hub and should provide me with plenty of scope for gearing.

I opened up the cylinder head inlet ports to take new 30mm carbs on rubber mounts before sending it of to Dave Degens for a new set of thin stem valves and matching guides which should allow it to rev safely up to almost 9000rpm. He also fitted oversize exhaust stubs and delightful little ball-jointed tappet adjusters that give much better contact with the valve stems. The new exhaust stubs did however mean I had to modify my lovely new Parravani headers which caused me some distress, but I’ve made up a pair of big bore, un-silenced pipes as well for the meetings with no noise limit. These are based on a system fitted to the works 500s and sound awesome.

Also at Mr Degens suggestion even bigger carbs are to be fitted. Using tapered mounts will mean no further work to the head is required. While everyone else used higher and higher compression ratios with small standard carbs to get more power Degens’ Dresda Autos used bigger and bigger carbs with standard C.R. to achieve as good if not better performance with the better reliability and longevity that comes with lower compression. A pair of 32mm Wassal carbs are now waiting to join the fun.

Seat and tank were now sent off for painting in the same colour used by R.N. Triples.

It’s actually a Subaru  colour but matches the original Triumph blue very well. I’ve always done my own painting before but the difficulty with obtaining cellulose and the poor performance of the modern version plus the complication of 2 part plus lacquer application meant I entrusted it to a local car repair shop ,Colby Garage, and I’m very happy with the result.

All the temporary fasteners were being replaced with stainless now with heads turned and counter bored just because I could!

The primary drive was fitted with the new anodised ally clutch drum and the last Renold primary chain that Supreme Motorcycles had. Capped off with an ally pressure plate it’s a shame to cover it up but as the crankcase now breathes through the primary case it has to be sealed up oil tight. A turned spigot projects from the primary chain inspection hole with a large bore breather pipe to a catch tank attached.

The CNC clip-ons were swapped with period Wassell ones off my 250 as the originality bug took hold. The only concession to modernity is the ignition system which you can’t see at all but which should give reliable battery free running.(eventually)

Having retired from teaching Karate just before I became ill a very nice Scitsu rev counter was now ordered as my leaving gift. It had not been possible to obtain it earlier as the final decision on what type of ignition system to use had not been made. This explains the rather incongruous detail of a rising sun badge in the middle of a Triumph’s rev counter.

With the paintwork back and the carbs arriving in the post on the Saturday before the Skeyton Goat Classic Car and Motorcycle Show in May 2012, the not yet running Bob had to go for his first public outing. Reactions were good to say the least.

The following weekend, with fuel and oil pipes fitted, it was time to take the plunge and try to fire it up. Nervously turning over on the recently acquired roller starter, which Jef and I had jointly purchased in recognition of our advancing years, oil pressure was built up with ignition off and then the kill switch flicked to “On”.

An instant crescendo of sound bounced off the garage wall as the two un-silenced meggas

announced “Bobs alive” to the world.

Gibbo