Riding the winners! Bruce Main-Smith tells his story.
Motorcycle Mechanics, June 1970
Too fast for owner! Classic words applied to frantically fast machinery and every bit true of the 745 cc Kuhn-Seeley racing Norton.
Mick Andrew seems to be explaining something to Bruce
Main-Smith while Frank Kately sits on the Armco at Paddock Bend.
It was a very foggy morning in early February.
Tested at Brands Hatch, exclusively by Motorcycle Mechanics, the twin-cylinder racer was probably hitting about 110 to 115 mph at the shut-off point for the 70 mph Paddock Bend at the end of the 1.24-mile circuit's main straight. Why probably? Surely you can read the tachometer and convert to mph using the gear ratio and wheel size? Unfortunately not, because all you get on a super-tuned 750 on a short circuit is a flash reading on the rev-counter. The problem was this, the rate of acceleration coming out of 40 mph Clearways, the bend leading into Brands' main straight, was so great with some 70 bhp on tap, that I was reaching the end of the straight before top gear had gone home. In fact, the bike was still picking up speed.
On arrival at Paddock the correct line has to be chosen and about 60 mph gradually lost. The changing camber of the track has to be allowed for, the right gear selected and also the rev counter has to be watched to make sure that fourth gear isn't held fractionally too long.
Paddock is a very peculiar bend. In fact, unique in racing. On approach, the rider doesn't brake hard. He has to lose just enough speed at just the right rate, for the corner doesn't begin suddenly but gradually. Braking hard means the opposition comes steaming by.
With the 750 Kuhn-Seeley I was overhauling everything else in sight during mixed open practice. Result of this is an amount of threading through traffic with a 30 mph speed differential. So I had my wits about me and not much in the way of eyes on rev-counters!
The engine, basically a 745 push-rod Commando prepared by Gus Kuhn, the London Norton agent, for racing, was very, very smooth indeed.
Actual engines are erected by Jim Boughen, ex-AMC race-shop mechanic. On our test day, Kuhn had a brace of them, one with a fairing and being ridden by the Kuhn-Shell teamster Mick Andrew. The other was a naked version for the try-out of the new boy in the team, Pat Mahoney.
If there is one trait of the motors that stands out there's two of them. Which Irishism means that I found it hard to say which impressed me the most - the uncanny smoothness of the way the power came boiling in, or the fact that despite very big megaphones, these twins are quite free from megaphonitis, the misfiring that occurs when the motor runs out of the power band.
The camshaft is a Kuhn special. Other work on the engines includes high-compression pistons, head modifications with ports opened out to 32mm, bronze valve guides, Nimonic exhausts, polished and balanced con-rods, a rebalanced crank-shaft and a Seeley-type breather.
Transmission comprises an Atlas clutch and five-speed gear-box internals by Rod Quaife. But it is the cycle parts that are least Norton. The frame is a Mk III Seeley, as are the alloy petrol and oil tanks and the duo front brake.
Teles are Manx, so too is the rear wheel. A Girling hydraulic steering damper is fitted. This little lot sells for £800 in a limited state of tune. Price tag is upped to £875 for a full tweak. Lots of money, but lots of go.
Like all 650 and 750 racing Nortons I have ridden before, there was power low down, a pretty easy climb on to the maximum power and no particularly marked cam effect.
Contrast that with a 500cc Domiracer, which is all rev and lots of desperate searchings in the gearbox for the right cogs to keep the rpm up in an area where there is some steam.
With the Kuhn-Seeley I could drive it pretty much as I wished. I revved it round Druid's Hill 35 mph hairpin in bottom, and I plodded it round in second.
Both gave results. In any case there's so much power on tap in either gear when banked over on the footrest, that I didn't dare screw it all on . . .
That's big-engine beef for you!
About 6000 rpm seemed a natural peak with the next ratio nice and close, so I didn't have to worry about dropping out of the power band. Vibration was totally absent.
I've ridden other 750 Nortons which had some degree of harshness and with which good attention to the tachometer was essential.
This one was so sweet, and it let me more or less forget about its instrumentation.
Gear changing was slick, and clutch action delightful. Kuhn managing director Vincent Davey could have cogged it down so that I used the upper four. His 750 was equally happy at Brands on the lower four.
At Snetterton it would have been important to gear fifth for the Norwich straight and first for the hairpin - thus using all five ratios.
This was not the first Seeley I've ridden by any means, but it was the first with a 750 plot in it.
Frankly, I felt a little dubious because Colin's layout leaves all that lump down front without any tubing round it. So, what does this mean? Kuhn mechanic Frank Kateley told me that the support is so good that the engine stays put perfectly, even with the head-bracket bolts left out! And obviously, the results are the things that count, so a truism has it. And you only have to look up the winning places.
Also the Kuhn-Seeley 750 steers remarkably well. So good in fact, I have neither criticism nor suggestions to offer. Braking power also felt fine, not that Brands is a very hard circuit for the stoppers. The double front unit was as gentle as only a drum can be, but certainly as powerful as a twin-disc set-up. Full marks to Seeley.
Lever pressure was light too, which is not always the case with some types of compensators for double-sided stoppers.
I have no particular comment to offer about the 8 inch Manx back brake. These always strike me as being more or less up to the job provided that the combination of a brake-murdering circuit - like Silverstone's Club gallivant - and a weak front anchor doesn't arise.
Then the Manx gets hot and bothered if the engine is powerful enough to propel the bike at a respectable gait. But on the 750 Kuhn-Seeley, that circumstance doesn't crop up thanks to a very potent front unit.
Pedal pressure for the back brake was highish, a normal Manx characteristic, thanks to both bikes being tailored to take monster men like Mick. I could get my feet to the pedals and my head down behind the screen. And a very effective screen it was.
I have no doubts whatsoever that with this glassfibre fairing and the Commando power unit, we are discussing a 145 mph bicycle.
Not even at the top side of 110 mph. coming towards Paddock, was the edge of the perspex beginning to judder from wind effect, as is too often the case.
The only criticism I have is the very limited lock which makes the bike hard to wheel about in the pits. It has always puzzled me why race regulations prohibit more lock. It is, in fact, lock that gives you a chance of getting out of trouble if the back end starts a slide ...
Both bikes were infallible starters even in the bitter cold of Brands Hatch in winter-time. A couple of smart paces sufficed for the run and they fired up at the first bump. The weight penalty of carting around a 12-volt battery for the Lucas ignition seems to pay its dividend.
One amusing incident bedeviled Vincent Davey and that was restarting. Pat Mahoney's 750 was completed only the night before our try-out. Mick Andrew made repeated attempts to get it to start, doing the traditional run-and-bump following the standard ritual. This consists of hooking the gear pedal up until bottom is engaged, rocking back on compression and then doing the usual patter with the feet up the road.
But its Quaife camplate was in upside down and what he thought was first was really fifth. Naturally, it didn't burst into life ...
Brands is a tester's circuit. It shows up bikes' failings. Going into Paddock you want even running on a light throttle, a clean re-application of power at the apex and good front fork action if a slower rider forces you to the outside kerb at the exit.
The Kuhn-Seeley scored well on those. Round Druid's you need either just the right gear or low-down power to take the corner "one cog up". Full marks. Going round the first left-hander, you can lose either the front or the back wheel on a damp patch. Nice. At the next left-hander you can usually have the paint off the fairing or gronch the clutch cover. I had all the ground clearance I could use. It was really well over.
Kidney Bend tests the ability to flick from left lean to right. The Seeley can do it. Clearways seem to test everything, from rider stupidity to wheel adhesion. You might lose the back near the apex and in a big way. On the exit the back may again go but you can usually remain the captain. I thought the Kuhn was in fact hanging its tail out a bit.
Into the straight and you may get a bit of a front-end wobble. Derek Minter's Cotton Telstar used to nod its head badly just there. Full marks to the Kuhn-Seeley again.
Which just about sums it up. Full marks to Vincent Davey of Gus Kuhn and to Colin Seeley on liaising to create a very fine racing motorcycle indeed.
These three words are a complete picture - very fine indeed.