Sunday, September 06, 2009


Gernot Schuh has kindly answered some of my technical questions regarding the modifications to the J.A.P. KTOR engine in what was formerly a normally aspirated, racing 1925 Zenith. The first incarnation was surely built under the supervision of Freddie Barnes himself, who personally oversaw all of the 'big gun' racers which exited his factory doors.

While we don't yet know the early history of Super Kim in England, it's useful to recall that this small company holds the distinction of more Brooklands 'Gold Stars' (for a lap over 100mph during a race) to its name than any other. This Zenith was originally built for a purpose - going fast, preferably faster than any other machine available at the time. Thus, it is no coincidence that the Sigrands chose a Zenith (over say, a Brough Superior, MacEvoy, etc) to bring home to South America; the Zenith had the reputation as the Fastest Machine You Could Buy for track racing in the 1920's. George Brough may have claimed differently, but the records at Brooklands tell the tale. Zenith was the Bomb.

Some technical notes (my words combined with Gernot's here):

The bore and stroke of this monster are 94.9x120mm, giving 1700cc, with a compression ratio of 6.6:1. Combine this with the blower's nominal delivery volume, this would give a corrected compression at maximum revs of 15.8:1 !

How can this work, especially with the carburettor setup, which we found to be for petrol rather than alcohol? The 'racing' cam timing holds the clue; the supercharger's efficiency, combined with extensive valve-overlap from the engine's unblown racing days. An 8.8mm valve lift on both exhaust and inlet valves at maximum 'bump' leaves about 4mm of valve opening at TDC! The incoming charge, blown past the partially open valves, would theoretically keep the exhaust valve in particular just a bit cooler, helping it survive in the very harsh combustion environment with such a high C.R.

The gearing pencils out for 260km/hr @ 5000rpm (156mph) in third gear. Wheelspin above 120mph probably would keep the maximum a bit below the theoretical top speed. Super Kim uses a three-speed Sturmey-Archer 'Super Heavyweight' gearbox, one of six ever built for record-breaking, and I believe, the only on not in use on a Brough Superior. Was it originally specified thus from Freddie Barnes? We don't know yet, as we don't know whether the machine was purchased new from Zenith, or in 'used' condition after a few seasons at Brooklands.

At maximum revs of 5000rpm, the piston speed is 20m/sec, a figure typically recommended as safe for racing in the engineering literature. The extensive piston drilling is a relic of 'Teens and Twenty's racing practice, when lightness was a premium (especially during the days of cast-iron pistons!), and engine revs were fairly low. Such drilling was also typical on connecting rods, and just about any other moving part in the engine! By the 1930's, as metallurgy improved, such 'cheesework' became obsolete and unneccessary. The pistons in Super Kim are clearly made in-house, as they're of a design I haven't seen, although it's possible, with such a large bore, that they came from a car.

Overall weight dry is 215kg (473lbs), which is really light for a Land Speed Record machine of this capacity; weight per se isn't a factor in top speed, only acceleration, and in fact, greater weight is an advantage in keeping the motorcycle stable, with both wheels on the ground, and helps minimize wheelspin. Having ridden rigid-frame racers at well over 100mph, I can attest that they aviate! A little avoirdupois certainly couldn't hurt, unless there is limited space possible for a straight-line run - a point completely relevant to a speed record in Argentina, which has few roads (or beaches) capable of a full-throttle, multi-mile record attempt. Quick acceleration might have been essential if only 3 or 4 miles of smooth straightaway were available.

During his rebuild, Gernot replaced the half-time pinion in the cambox, and the right-hand main bearing, and all the ball races in the drive side, along with the chains, tires, valves and springs, ignition cable, and about a dozen smaller parts. The camshaft and roller followers were refaced. All of this work took 320 hours, which includes 120 hours of deep cleaning and rust removal!

Asked if there were any surprises, Gernot says, "Suprises? The capacity, sure. Hmmm....and the twisted history, that is absolutely fascinating to me. That there is contact with the family. And so much appreciation for my work."

And how does it SOUND? "Like a tractor on drugs; on revs, it lets out a ROAR..." He adds, "The most important thing is: it runs, despite so many experts, who claimed it would not, and looks more like a racingman's hot dream. The inspection showed that it was used, at least for testing. There were traces of use on the cylinder walls, oil carbon here and there, and in the gearbox there was heavy wear between the mainshaft and the tubular shaft where the sprocket sits. This odd plate, that clamps the gearbox at the pin, were the kick start was once located, was not part of the original design."

To this I would add my own story with Super Kim. I was first introduced to photographs of the bike at Jay Leno's garage, 18 years ago. The seller, Hector Mendizabal (r.i.p.), claimed it was a Brough Superior, and it clearly wasn't, but we didn't at the time know what exactly it was. A bit of research on my own revealed it to be a highly modified Zenith, but the asking price was over the top at the time. By coincidence, I purchased a BS SS100 engine from Mendizabal a year later, and the Zenith came up again, still over-priced. I purchased the machine 11 years ago from the man who actually posessed Super Kim, for half the original price, after a tip-off from a Brough-owning friend in Germany.

I was warned at the time by 'experts' that Super Kim was a fake, a lash-up, a South American piece of trash, not worth the money, and that I would surely be defrauded at best, possibly shot at worst! I've spoken on this site before about the 'aura of fraudulence' around machines from South America, which hovers in the mind of North American and European bike collectors. That mindset persists to this day, and is evidenced by Gernot's own comments above regarding 'doubting experts'.

When I attempted to sell Super Kim 9 years ago, I was met with the same resistance, doubts, and scare talk. One Austrian fellow backed out of a signed purchase agreement, after being told by such an expert that the machine was basically worthless! I am fairly certain he regrets his decision nowadays... given that the last big-twin Zenith with racing history (unsupercharged) sold for $325,000.


Anonymous said...

Mark Hoyer directed me to your very interesting site - I see that you are the Griff Borgeson of motorbikes, sniffing out the long-lost and then presenting their stories.

I wonder if you could confirm or deny that the Irish racer/engineer Charles B. Franklin accidentally developed the idea of accelerating combustion by means of squish (later to be patented by Harry Ricardo) at Brooklands? And if he did, would you know whether or not he later, as an engineer at Indian in the US, applied this to his successful flathead/side-valve racers?

Kevin Cameron

Anonymous said...


I really enjoyed the recent Zenith and BS posts on your site. I will be seeing Mark no doubt over the forthcoming Beaulieu weekend.

cheers, Howard

Anonymous said...

I just fell over your website, very good.
A mate passed it on to me as I am a tiny bit of a JAP-nut.

So, I just 'wasted' a fair bit of time reading the Super Kim story....instead of working...I just checked my mail as I had breakfast and here I am, an hour later and no closer to work.

I build replica JAP engines for racing and road use, at the moment I am concentrating on the 8/80 racing model, the early one with speedway style heads and after that I will make the later 1948 Mk2 models.
But, I would dearly love to build a '20s version for sure....but I have no patterns available for that top end yet.

I have a big framed photo of Joe Wright seated on a blown OEC JAP that was purported to be the one that broke the record in 1930 looking down at me as I write dream is to build my own supercharged JAP, '20s model, and take it to the Lake Gairdner salt lake one year.....I've been up there (about 6 hours NW of here) for a look so I can see if I would like to get out there on a bike myself. Hell! Yes! day, and I now hope it will be JAP-mounted.

These current engines are for guys who will race them in historic road racing and speedway. Naturally the speedway engine is going into a sidecar as is one of the current road racing engines, the other ones are going into solo road racers.
I machine the castings myself and make the cranks, the only bought parts are the Carrillo conrods and big end bearing and mainshaft caged needle rollers, I make all the baring surfaces myself.
Heads are out at the moment for valve seat cutting and the cylinders are out getting bored, I don't have machines for doing that sort of thing, I concentrated on having a good mill, lathe, internal and external surface grinders......haha, my internal grinder is an old war time Moore Tools jig grinder, older than many of the bikes it makes parts for! Made in Brodgeport Connecticut, just up the road from Bridgport Mills, it is a delightful vintage machine itself, having come to Australia as part of the wartime Lend Lease program....I know it's whole history ....yadda, yadda yadda...sorry I do go on a bit.

I've made a lot of jigs and tooling for these engines and have tentative further orders, I intent to farm some of the stuff outside next time, to people with CNC and other auto machinery...things like head studs and their thimbles, valve guides, valve covers etc...simple but time consuming stuff to make on my manual machines. It looks like there will be about 3 engines in my next batch.
If you are interested I can send you some more pics and some of the story.

Great website, I can see a late late late night coming up tonight when I settle in a read the whole thing, but for the moment I have to go-a-JAP-building.

Greg Summerton
South AUstralia

Anonymous said...

Hey Paul,

I occasionally drop in on your blog - there is always something to
read/look at. Very impressive.

cheers, Simon

pioneer rider, and another friend of Mark's said...


Glad to see your post. I'm a fan, and love to read when you write about tech in Cycle World. Especially when you show how so many things were developed in the early days, only to be brought back by the manufacturers of the 60's 70's and 80's.

Maybe you'd like to do a special column on the c1913 Scott, or the '20s Rudges. Everything old is new again.

Pete Young

John E. Adams said...

A wonderful follow up on this amazing machine Paul -;0)



Anonymous said...

Hi Paul,
I've been catching up on your blogs.I've been traveling for another two weeks.
I vaguely remember this bike from years ago.Probably when you had it. I went to Buenos Aires in 91 and bought out a shop.People's attitudes towards Argentines is about the same as meth dealers in Tiajuana.I enjoyed myself and my stay down there (except for getting sick).They are kind of desperate people having had Peron screw their economy up for years to come.
There is some killer stuff down there.They are gearheads supreme.All of the vintage stuff in South America gravitates down there.

We are still getting calls about Gunga Din being a fake.I had an email from a guy who worked at the factory in 1955 and he remembered the day that the cases were replaced.
Who woulda ever thought you'd be getting emails from ex-workers?!!


Anonymous said...


Thanks for your Vintagent web/blog, some nice stories and photos there... I always enjoy my trip there!!!

But how could you part with THAT Zenith?????????????????? I'm speechless at its beauty.........

I thought I just mention something...It's about the French Majestic: it is NOT a "New Motorcycle"

George Roy, the builder/inventor of the Magestic did indeed build a bike called the "New Motorcycle", but it was before and in another company than the Magestic. The NM was like a normal bike, "space frame" a la Zundapp so to speak, made out of manually bent metal sheets. Chaise motors as well for these earlier Roy creations. So the NM failed and went bust so he went further in his new company/own style and the Majestic is the apotheosis of that. It still wasn't a success, so Chaise bought him out, changed the design a bit to make it cheaper to build, still no success...

Have a nice day,

Patrick Delli,
Frenchman living in GB
my web, racing Harleys:

vintagent said...

the Zenith bought me a house in SF, and so many important connections subsequently that it's been like a magic talisman. Friends in Argentina and Germany, Austria, England, Sigrands family history, Argentine motorcycle history, etc, etc. Truly, riches came from letting this precious machine go to other hands.

mp said...

Hi there

Great blog I have been reading it a lot. I am glad to see this Zenith bike being fixed up as it is one of my favourite bikes.

Will there be a Youtube video or something of it running???

please let me know if there wil be or maybe you could make it happen?

Thank You

Anonymous said...

very intersting your info about Mr Robert Sigrand of argentinia.. In fact his grandson ( Ignacio) is visiting) me tomorow to have a look at my 1920 DS motorcycle made by his grandfather.; It is probably the first Deblades & Sigrand build in 1920.

I will keep you informed

Attached are some fotos of the mentioned motorcycle.. It is beautifully crafted and compared to it's American competitors much lower-sportier-lighter-modern... the better motorcycle , no doubt

best regards
Bart Crauwels , Belgium

Tony Curr said...

Firstly, according to the book "Franklin's Indians", CBF applied his squish knowledge to the Powerplus and later developments so that they out-performed 8-valve and ioe (pocket-valve) existing designs. Secondly, the "orange-squeezer" shape of Super Kim's piston crowns may have originated with Ernesr Searle, a sprinter of the 1920s whose success led Nortons to employ him as an engine development engineer. Apparently the idea was to improve gas seal in a manner recalling the later Dykes piston ring. I960s Motorcycle Sport magazines are a good source.