72 AJS Norton Stormer

My chum raced a 410 AJS Stormer in Hong Kong in the early 70s, it had almost no flywheel effect and his ran backwards a couple of times when it was idling particularly slowly and he reved it up to catch it from stalling, it didn't seem to have the momentum to get it over TDC at that speed. He thought one of the other competitors was playing a trick on him by pulling him backwards, but there was no one to be seen.

I remember Fluff Brown very well, as I spent a lot of time with him and Malcolm Davis doing test work on the Stormer. I believe Fluff passed away a couple of years ago and his son is now running the business.

The Stormer's frame was definitely an N-V design and owed nothing to James, Francis-Barnett or anyone else. It was derived from the Commando, and featured the same large-diameter top tube. The major difference was that it was attached to the headstock near the bottom rather than the top, as the Commando was configured.

In competition we suffered three top-tube fatigue failures, which look exactly the same, but upside down, as those referred to as "widow-maker" failures on the Commando. I did a quickie analysis of the structure and showed that the gusset between the top of the headstock and the top tube made a stress concentrator of about 6-times magnitude, which was causing "oil-can" deformation of the top tube and failure in the top half. The same problem affected the Commando, with fatigue cracking in the lower half of the tube, just aft of the gusset.

Late production models had a top tube that was made up of two semi-circular tubes with a triangular filler between them. The two semi-circular pieces were welded close to the top and bottom of the headstock, and came together at the back of the seat pan as a circular tube. The triangular piece was welded in to make a complete tapered ovoid structural item. i wanted to do a logarithmic curved piece, to match the stress concentrations, but was shot down on costs.

I wish the Commando folks had taken that design instead of the extra tube installation. At least it would have looked more professional!

Here's a warning for anyone "tidying up" wiring on a roadable Stormer. Someone posted on the Commando section the other day about hiding the wiring inside the frame tubes. Whatever else, DON'T do this on a Stormer. The top tube is highly stressed and susceptible to fatigue failures. We had several frames fail during competition while I was involved at N-V. Fortunately, the fuel tank was strong enough to hold things together and there were no injuries due to the frames failing.

Holes drilled through parts under high stress levels in action are major stress raisers, particularly if they aren't on the horizontal center-line of the tube. Burrs round the holes are even worse.

In 69/70 AJS had works riders Malcolm Davis, Andy Roberton and Bengt-Arne Bong. I'm not sure how long the latter was on the payroll, but I remember Fluff telling me that he was the fastest, hardist, most destructive rider he had ever met. He told a story about the Stormer rear wheel, which was generally thought to be pretty robust. B-AB destroyed a rear wheel in about an hour. Thinking it was a fluke, the team put in a new wheel, which B-AB destroyed even quicker.
I always thought that the 250 was a "sweet" motor, whereas the 370 and later 410 were fast but rough, not pleasant to ride.
cheers
wakeup

I don't remember Andy Roberton being on the M-X team at the time I left (May 1968), but I remember Malcolm Davis and Fluff Brown quite well. I agree that the 250 was a good-runner and relatively low vibration. The "360" was more of a rattler, and I can imagine the 410 being a real beast.

The last time I saw those guys was when the team came to a motocross meet in Washington State as part of a US tour - must've been spring of 1969, I think.

Were not the Stormer frames designed by the same clever ex nuke industry person who designed (designed ..ha ha) the original Commando frames that failed in exactly the same place?? Luckily someone had the brains to consult Reynold who suggested some changes that triangulated the headstock and cured the problem. The idiots at Norton had suggested increasing the thickness of the top spine......Reynold people can probably remember how many laps on the 'cobbles the original design lasted before failure which I believe was 26 while the thicker tube version lasted about 100 laps and the Renold suggested version simply refused to fail and it was even sent out scrambling on the tank course in an effort to induce a failure...... Clearly the designer was incapable of learning.....mind you we had a few like that at Marconi......

J. M. Leadbeater said:

Reynold people can probably remember how many laps on the 'cobbles the original design lasted before failure which I believe was 26

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23.

J. M. Leadbeater said:

while the thicker tube version lasted about 100 laps

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120.

(Both figures according to a gentleman by the name of Ken Sprayson whom no doubt you have heard of)

It was a little bt different than posted. The "ex-nuke" guy referred to might have been our Managing Director, Dr. Stefan Bauer. He had an engineering Ph.D and had worked for many years for Rolls-Royce (Aero Engines). The original Commando was heavily influenced by him, as he was paranoid about vibration. The design chief at Wolverhampton was Bob Trigg, probably in his early 30s at the time (I was 25 when I joined).

The Stormer was clearly designed along the same lines as the Commando, but I don't know why the top tube was attached at the bottom of the headstock, rather than at the top, like the Commando. The fatigue failures that the Stormer suffered were exactly like those of the Commando, except on the upper half of the tube. As far as I know, the design change that incorporated the triangular "filler" in the Stormer top tube solved the problem. I don't know how long the team continued to compete in M-X as the company went down the toilet. I was too far away and too much involved in adapting to the US and to Boeing's way of doing business, I didn't have time to keep tabs on N-V.

Because of the very poor coordination between Wolverhampton and Plumstead, I doubt that the London guys knew about the failures. The road environment the Commando operated in was much less harsh than the M-X competition track, so it took a lot longer for the problem to appear.

There was certainly an AJS Stormer moto cross effort in 1970. The works team was at least Malcolm Davis and Andy Roberton, (and possibly Bengt Arne Bonn) at about the mid point of the season they were very well placed in the 250 World Champs standings. I don't remember how long that team stayed the course, but at some point Vic Eastwood was riding for AJS, but mainly in National events I think. Development seemed to concentrate on the over 250 motor.
Clearly things got a bit tense in the mid 70s!
Fluff Brown bought the "AJS" name and production rights for the Stormer, when NVT hit the wall
cheers
wakeup

These were very good handling bikes, they had slightly forward mounted rear shocks before the advent of long travel suspension, however the engines were not so competitive and down on power compared with other marques like Husqvarna, Bultaco and the Japanes bikes that were just then challenging the European MX bike's superiority. They rapidly became obsolete and for a number of years you could buy them for peanuts still in a crate from dealers who had been unable to sell them when they were new.

I have ridden both the 250 and the 410 versions, the bigger machine had such a light flywheel that it could run backwards if you let it idle too slowly or too long. Roger Harvey (British national 125 champion and GP rider) told me that the frames would break on the open class bikes.

One problem we found during my routine "ride-to-work" use of a 250 Stormer was engine "mini-seizures" accompanied by serious cracking of the cooling fins round the exhaust port. We found it by a fortuitous "what's that odd ringing noise" question when I pulled into the shop one morning. We pulled the barrel off and found a series of ridges in the inside surface near the exhaust port and several cooling fins seriously damaged. The ridges were about 1/8" deep, 3/8" apart and ran about a third of the way round the cylinder wall. The piston rings were also damaged. I'd ridden it less than 500 miles from new.

The problem was judged to be pre-ignition on part-throttle running, causing the cylinder to get very hot around the exhaust port and breaking down the lubricant in the gas/oil mixture. The piston rings were welding to the cylinder liner and then breaking loose, re-welding again further up the bore and repeating maybe for 3" of the stroke. On the M-X team bikes, there was very little part-throttle operation, so the problem hadn't shown up.

We put a new cylinder barrel on the engine and switched back to Castrol "R" in the gas instead of 2-stroke mix on the test bike and that solved the problem temporarily, but it was a pain having to shake the bike to re-mix the oil and gas every time it had been parked more than an hour or so.

I left N-V before the production bikes went on sale, so I don't know what the final fix was.

Frank, I found your posts very interesting and informative. I am new here and while researching AJS Stormer I came across your posts about stormers. I am in the process of taking apart a nice bike but it has been parked 40 years and has a seized piston. A 250 stormer engine which I soaked in Marvel Mystery oil for a couple days in hopes of freeing the piston. It worked! It had the heat damage at the exhaust port as you described. I will next be splitting cases to replace main seals. A couple questions. Is the piston pin a press fit? I am used to pushing wrist pins out by hand but I'm being carful since it seems stuck. Also any advise on removing the clutch? It is not like the type of clutch I am used to. I have a shop manual on order. I just bought an AJS clutch tool. There is a lot I need to learn about this bike. Thanks again for your posts and the others here as well.

I'm not sure about the wrist-pin. I suspect it may be an interference fit in the piston. If there are no circlips keeping it in place then it would be interference. It would be a bit easier to remove if the piston was hot.

I'm a bit surprised that a ''71 bike would have the seizure "ripples" in the cylinder. I thought the problem had been fixed before the production Stormers hit the street. Castrol "R" would solve the problem, but it's a pain to have to shake the bike before you start it. On the prototype, the ridges were too deep to machine away after only about 500 miles. Are the cooling fins around the exhaust port cracked? That was the other clue to the overheating.

Good luck with your project. I've considered trying to find a Stormer, but I think I'm getting a bit old (74) to take up bikes again. I quit after moving to the US in 1968. However, I did meet a guy at a local club that still rides at 82. He has a 2 year-old Triumph and an early 60's Matchless 500cc scrambler. Since he has an artificial knee, he converted the Matchless to electric start.

Frank

Frank,
My Stormer is suppose to be an early 1969 250. The bike was seized but did not have damage to the bore that I could detect. Outside the exhaust port It did have a lot of melted aluminum in the exhaust port just past the metal sleeve and a couple cracked cooling fins near the exhaust port. I still hope to reuse the cylinder after a hone and if needed a rebore. I just now took engine out of frame. I took a second look at the clutch and can't seem to get the center nut off. I will wait till I get the shop manual to proceed. I will try to post photos later after cleaning it up. The piston does have clips on the wrist pin which are out so may try heating up piston as you suggest. thanks
Mark

Mark:

I understand a little better with the "early 1969" date for your bike. I left for the US in June 1968 and we'd only found the problem a few weeks earlier. I got the impression, from talking to Peter Inchley when the M-X team were in Seattle in the fall of '69, that they had solved the problem prior to the Stormer entering the retail marketplace. It was still "in development" when I left.

Maybe if you got in touch with "Fluff" Brown's son, who I understand is still running the AJS business, he'd be able to advise if there was a fix. From what you've said about the ridges and damaged cooling fins, that bike was too early to have it. I'd suggested thicker and bigger fins in that area and a "bridge" in the fin configuration that would conduct more heat away from the center of the exhaust port. As I remember, there was no heat conducting material directly across the bridge in the liner, which was there to prevent the rings from snagging on such a wide port opening.

When you get to where it will be runnable, I'd strongly advise running with a Castrol "R" or equivalent oil in the gas unless you've heard from AJS what the fix was.

The Stormer is a fine machine to ride. I thoroughly enjoyed my daily commute on it, even though it was only about 10 miles each way. When I was commuting almost 50 miles each way, my ride was a rather tired old company 650SS. Despite it having 130,000 miles on it (according to the odometer) that was a good ride, almost all on country roads with very little traffic. When the 650 went back to London for a development program, it was a shock to get a 50cc Italian bike called a "MOTOM" for the trip. The Villiers "Fantabulous" scooter (a 200cc machine made in India) was an improvement over the Motom, but I was sure glad to get the 650 back again. Unfortunately, riding it back from my home town in Lancashire just before I left the company, the oil tank split open when I was cruising on the M6 at about 85 mph, and the engine seized. I don't think the old girl was ever repaired.


Frank

Hi Frank,

Any idea where the name 'Fluff" came from?

Thanks,
Graeme

Sorry, Graeme, I have no idea. He was known by everyone as "Fluff" and I have no idea what his "real" first name was.


Frank

frankdamp said:

He was known by everyone as "Fluff" and I have no idea what his "real" first name was.

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David George Brown.