Honda-SOHC
Other Stuff => Misc / Open => Topic started by: Tony.B on December 12, 2023, 08:10:06 PM
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Thought some of you might find this amusing. Way back in '79, as a 17 year old looking for my first 'proper' bike after my moped, a blue Suzuki AP50; I was reading an article in Motor-Cycle Weekly, (I preferred it to MCN). They featured a 250cc conversion for the 400/4 offered by Hertfordshire tuning company, Jock Kerr racing developments. All my mates were buying RD, XS and various Honda 250's, and I've always liked to be different. Anyway, after trading in my Suzuki at Keith Manning motorcycles in Wokingham, I found myself the proud owner of a Honda 400/4, in red, reg number NDP 85R.
I booked it in with Jock Kerr's for a few week's time, and had to just wait. Naturally one Saturday when mum and dad went shopping, I couldn't resist taking it out for a quick blast up the A30 to Blackbushe airport. I only went about three or four miles, but it scared the life out of me, after a 50cc moped, it seemed like a rocket ship!
Long story short, after they had converted it to a 250, which consisted of sleeving the cylinder and using smaller pistons, which left the combustion chambers mushroom shaped, it wasn't much faster than a 125, if that! It was frankly dog-slow, you had to take it to 11,000 in 5th, lay flat on the tank, and you could just about get 70 on the clock. It wouldn't even pull 6th gear.
If I had my time again, I wouldn't have bothered, but it was kind of cool to be 17 years old riding what looked to be a 400.
And yes, that's me in my avatar back then, you can just about see the 'L' plate on the bottom of the rear mudguard.
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So was that to get around the 250cc rule for L plates yet still have four cylinders?
Might have been easier to go for a 250 Dream or Super Sport they were pretty nippy back in the day.
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So was that to get around the 250cc rule for L plates yet still have four cylinders?
Might have been easier to go for a 250 Dream or DupercSport they were pretty nippy back in the day.
One of the arguments put forward by Kerr's, was that you didn't need to change bikes, especially back in those days with HP etc. You could have the same bike first as a 250, then a 400 when you passed your test, and then later use one of their big bore kits, or other tuning goodies. They did all sorts, including turbo kits, though mainly for the bigger fours.
I wonder if anyone on this forum had any experience of Jock Kerr's?
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Yes, i had a 600 kit for a 500 but it left the liners so thin it was unusable
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180cc version of a CB125S (room mate at Uni - not mine)
It was a dog.
As Bryan says, the liners were too thin and the head gasket kept blowing. Then it blew up completely.
There have been threads on here before about Jock Kerr…
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His race bikes were ok but they didnt have to last long
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Interesting, I'll have to peruse the forum some more...........
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Wasn't he a sidecar racer too?? World champion etc...
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Wasn't he a sidecar racer too?? World champion etc...
You're thinking of Jock Taylor!
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Wasn't he a sidecar racer too?? World champion etc...
You're thinking of Jock Taylor!
Doh! That will be the one!
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Re Jock Kerr Motorcycle Developments Limited (JKMDL).... I worked there for a short time during my college holidays in the late 1970's.. by this time Jock Kerr had sold up and I THINK he went to work at Eddy Grimstead's motorcycle / Scooter place in North or North East London. The owner, manager, etc when I was at JKMDL was Mike Sturgeon, as far as my memory goes he was a nice boss, had a business plan BUT did not know of the engineering or physics side of things...., engines, metal, heat, lubrication, balance, etc hence there were so many "Issues".. So to clarify things a bit, rocker and camshaft Stellite welding I think it was called, grinding, etc and ALL precision engineering work was done by a neighbouring company called Joy Engineering. At JKMDL we did engine stripping, assessments, rebuilding so the then rebuilt engines could be sold as reconditioned units, that meant your pressed up Honda CB125 single crank if it felt right it went back in, even if the engine had done 30,000 miles, it was only if the mains & big ends had plain bearings that were actually measured, and often only had new shells the surfaces were not re-ground, small ends were rarely touched, valve guides ditto. The balances of failures, returns, refunds were offset by the ability of JKMDL to weasle out of paying up, 'you did not do this' or "that's wear & tear", often asking for the engine to be sent back for assessment then taking ages to assess, often sending out another just as dodgy unit in replacement... The Mods, big bores, smaller capacities were virtually all crap.. The big bores were nearly always overbored standard bore liners so leaving the liners too thin and they cracked where the liner left the bottom of the cylinder casting, the 400/4 to 250/4 sleeving down was just an extra lining put in the standard liners with i think Honda C50 pistons, making the liners too thick to dissipate the heat, ok at start up, ok for short runs but give it some welly or constant 60mph and the pistons would seize... the 250 Superdream conversion to 125cc was a topless piston in one bore with the rockers removed so making it a VERY vibratory 125 single that if it lasted without falling apart from the vibrations it would blow the crank in 500 miles.... The list goes on and on, I only stayed there as I needed the money and I had access to the workshop, my job was on the Honda singles range C50 to CB125 OHV & OHC.... After JKMDL closed the company went onto making rubbish chromed & non-chromed 4-stroke noisey exhausts that often lessened the bikes power and always got you nicked, sold from a shop in I think Market Place or square, Hatfield.. Shame really, the potential was there just not the brains.
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Interesting input from someone who was actually there.
My Uni room-mate binned the CB180S for a 400/4 and promptly got nicked for speeding on the A23 north of Brighton.
104mph the ticket said.
He dined out in that for years.
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I remember the turbo 400/4, didn't Motorcycle Mechanics test one? I remember they did have a bit of a reputation at the time.
Nice history of the place and thanks for sharing.
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Nice bit of history written there. Thanks!
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I only went about three or four miles, but it scared the life out of me, after a 50cc moped, it seemed like a rocket ship!
(https://tse3.mm.bing.net/th/id/OIP.ry8TMkrP1N5tniQG0Jyh9QHaFj?r=0&rs=1&pid=ImgDetMain&o=7&rm=3)
I hear you! I started biking in 1981 in Germany, I had bought a 15mph moped (called a Mofa in Germany) for commuting, a Hercules Prima Presto ( see pic, try not to laugh! ;D )enough though for the bug to bite! So I went for a full licence. Things are done differently in Germany, very differently. You don't swan around on your own with L plates. You are under instruction usually following a car with Fahrschule plates, that means driving school, this is after some time on the playground and classroom, my instructer was an impatient bavarian who was fond of his loud voice. ( I'll try not to mention the war! ;D )The bike supplied by the school was a BMW R65, it felt like getting on a horse. After about five hours on the roads, it was time for the Autobahn :o Speeds of 80-90 mph (145 km) ....I felt ill, especially when overtaking big trucks! :o
After two weeks, time for the driving test, I flunked because I failed to look over my shoulder a few times on the playground test. I took another test a week later and passed. Three weeks after deciding to go for it I had a full bike licence, they don't waste much time!
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Re Jock Kerr Motorcycle Developments Limited (JKMDL).... I worked there for a short time during my college holidays in the late 1970's.. by this time Jock Kerr had sold up and I THINK he went to work at Eddy Grimstead's motorcycle / Scooter place in North or North East London. The owner, manager, etc when I was at JKMDL was Mike Sturgeon, as far as my memory goes he was a nice boss, had a business plan BUT did not know of the engineering or physics side of things...., engines, metal, heat, lubrication, balance, etc hence there were so many "Issues".. So to clarify things a bit, rocker and camshaft Stellite welding I think it was called, grinding, etc and ALL precision engineering work was done by a neighbouring company called Joy Engineering. At JKMDL we did engine stripping, assessments, rebuilding so the then rebuilt engines could be sold as reconditioned units, that meant your pressed up Honda CB125 single crank if it felt right it went back in, even if the engine had done 30,000 miles, it was only if the mains & big ends had plain bearings that were actually measured, and often only had new shells the surfaces were not re-ground, small ends were rarely touched, valve guides ditto. The balances of failures, returns, refunds were offset by the ability of JKMDL to weasle out of paying up, 'you did not do this' or "that's wear & tear", often asking for the engine to be sent back for assessment then taking ages to assess, often sending out another just as dodgy unit in replacement... The Mods, big bores, smaller capacities were virtually all crap.. The big bores were nearly always overbored standard bore liners so leaving the liners too thin and they cracked where the liner left the bottom of the cylinder casting, the 400/4 to 250/4 sleeving down was just an extra lining put in the standard liners with i think Honda C50 pistons, making the liners too thick to dissipate the heat, ok at start up, ok for short runs but give it some welly or constant 60mph and the pistons would seize... the 250 Superdream conversion to 125cc was a topless piston in one bore with the rockers removed so making it a VERY vibratory 125 single that if it lasted without falling apart from the vibrations it would blow the crank in 500 miles.... The list goes on and on, I only stayed there as I needed the money and I had access to the workshop, my job was on the Honda singles range C50 to CB125 OHV & OHC.... After JKMDL closed the company went onto making rubbish chromed & non-chromed 4-stroke noisey exhausts that often lessened the bikes power and always got you nicked, sold from a shop in I think Market Place or square, Hatfield.. Shame really, the potential was there just not the brains.
Nice insight, thanks for that. Were you the mechanic who came off it road testing it after the bike went back for its conversion back to 400? It cost JK a new tank and Cibie headlight!