AJS Stormer Main Page 

On this page you can find out where to buy vintage Stormer parts, obtain tips and information, check specifications, torque settings and contact us for technical help.

 

We still have tons of new Stormer parts in stock.

Some parts are New Old Stock, and some are newly manufactured.
Our GRP fuel tanks are made extra thick, from the latest ethanol resistant resin.

We deliver parts all over the world.

Many parts are available in our on line store.


If you cannot see what you want in our store, or you need help, contact us, and we'll be happy to help and advise you.

Remembering "Fluff" Brown

NEW! Folding Kickstart levers

The AJS Y4 (Stormer) is celebrating 50 years since it's first year of production. The Y4 was inaugurated in 1968. The first private rider to score a win was Alan Arnott on Sunday 16th March 1969 at The Kiwi Club's scramble at Bulford Down, Wiltshire.
Malcolm Davis won 250cc British Championships in 1968  and again in 1970, Andy Roberton brought the Stormer home in second place.
Read the amazing story of the AJS Stormer and the people who designed, developed and raced it, as told in the words of Cliff Stevens.

 Gear Ratios, Primary Drive Ratios and Primary Chain

AJS Stormer Tips & Frequently Asked Questions

Where are my frame and engine numbers?


The frame number can be in one of three positions:
1) On the steering headstock. (the frame sub-part number is 0700875)
2) On the top, left rear shock absorber mounting bracket
3) On the right swinging arm pivot plate.
The engine number can be found on the front of the crankcases between the front mounting brackets. Usually under a layer of black exhaust oil. Note: All Stormer (250,370 & 410) engine numbers begin with A250




What fuel & 2-stroke oil should I use in my Stormer?


From our experience, the best fuel / oil combination to run your Starmaker or Stormer engine on is: Premium unleaded fuel (BP Super Unleaded, Shell V-Power or similar high octane unleaded fuel) Enhance the fuel further by adding Fuchs (Silkolene) Pro Boost at 1.5%
For road and trail use, we reccomend a good quality mineral based 2-stroke 40w oil such as Fuchs Silkolene Super 2 or Comp 2 mixed at 32:1 For racing use, we recommend a castor based oil such as Fuchs Silkolene Casterene R40.
This oil is much better for the bushed small end bearing when under extreme load. This Fuchs Silkolene oil is a modern blend which remains stable when mixed with petrol, unlike the old Casrol R.




What oils should I use in my Stormer?


All the following information is based on our many years of racing experience:

Two Stroke Oil:
The best two stroke oil for racing is Fuchs (Silkolene) Casterene R40 (castor based oil) mixed at 32:1 This type of oil is particularly good for the plain bushed small end bearing. This modern vegetable based oil is far more stable when mixed with fuel than the old "Castrol R" oil from years past. Fuel separation is not a problem. It is also less likely to "gum" up and stain the engine casings. It still has the great "R" smell to it. For trail bikes, low stressed engines and general usage, use a good quality mineral based two stroke oil like Silkolene Super 2 PRE MIX or Comp 2, mixed at 32:1 NOTE. The use of modern, synthetic two stroke oils designed to be used at 40:1 and higher are not recommended. These oils will cause the plain bushed small end bearing to overheat and seize. Gearbox: Silkolene Medium Weight Gear Oil 85W 90. Quantity: 1 imp. Pint (570ml) Chaincase: Silkolene Light Weight Gear Oil sae 10/40 75w or Silkolene 10w Front Fork Oil
Quantity: 7.5 fl oz (210ml) Front Forks: Pro RSF 15 Racing Suspension Fluid. Use the better quality RSF non foaming oil to prevent fork "patter" on fast hard packed corners. Quantity: 7.5 fl oz (210ml) for standard Stormer forks. Fork travel will depict the quantity you need.




What should the piston to cylinder clearance be?


The following piston to liner clearances should be used for general and scrambles use. 250 Stormer/ Starmaker = 0.0025" (.064mm) 370/410 Stormer = 0.0035" (0.089mm) using Hepolite cast pistons. 410 Stormer = 0.004" (0.102mm) using Venolia forged pistons.




Should the clutch be wobbly on the mainshaft?


All Starmaker and Stormer clutch centres have a certain amount of free play on the main shaft splines, even from new. If your clutch cable has snapped inside the clutch casing, check for excessive clutch wobble, as the slots in the face of the basket can cut through the clutch cable. The excessive wobble is probably a combination of worn splines to either main shaft or clutch centre and/or excessive wear in the centre bearing #27831 After studying the clutch assembly, you've probably realised that it is not as straight forward as you might have wished to replace the centre bearing! and that the job will involve removing the clutch housing rivets. Arghh...! The solution... We have a modification, that once carried out, will make the job a piece of cake for subsequent bearing replacements and make the clutch housing & sprocket assembly a much stronger item. Firstly, weld the clutch basket to the sprocket using an electric stick arc welder (a bit tricky admittedly). Then machine out the inside of the housing to allow the bearing to be pressed out. Then machine a circlip groove in the housing, replace the bearing and fit a suitable circlip, to retain it. Job done! We can supply you with a suitable Circlip Part No.FB1357




Are there precautions I should take when washing my Stormer?


Put a plastic bag over the air filter & bung up the end of the muffler. Spray and brush the grime and muck with Silkolene "Pro-Clean" before you get the bike wet. Wash your bike down with a bucket of hot water. Only use additives in the water such as car wash & wax. Do not use house hold detergent as they usually contain salts which will corrode your bike's alluminium and chrome. After washing, always remove the contact breaker cover to allow condensation to dry out. Start your bike after washing off, to disperse any moisture from around the main and big end bearings, especially if using "R" type oils which emulsify with water. Remember to remove the filter cover & exhaust bung before you try and start the bike! Apply Silkolene "All in one" liberally to alloy surfaces and to the rear chain to disperse water and to prevent corrosion. Be careful if you using a pressure washer. Do not direct the washer at engine case joints or into wheel bearings. Polish & cherish! We use Solvo Autosol for the polished alluminium parts and a good quality car polish for the fuel tank and other glass fibre parts.




My clutch is slipping, or dragging what can be done?


There are several reasons why your clutch may slip or drag 1) Your clutch may drag if you do not have enough free play at the handle bar hand lever or at the operating scroll. You should have 3mm - 5mm at the hand lever. and 3-5mm free play at the tip of the scroll arm and Note: The operating pin bearing and thrust washers will seize if there is insufficient clearance.

2) Your clutch may drag if the clutch cable (#0700792) is not in perfect condition. Any stretch or sticking in the cable will reduce the amount of lift transmitted to the lifting arm. It is essential to use a good cable. Our new clutch cables are made for us by Venhill and are nylon lined.

3) Your clutch may drag if the clutch cotrol lever does not procuce enough pull. Some dog-leg levers, designed for modern bikes, do not produce enough lift.

4) Your clutch may drag if the spirolox circlip (#28216) on the right end of the gearbox main shaft has come off, or if the mainshaft is not shimed to have the correct 0.004" end float. 5) Your Stormer clutch may slip and drag if you have the early type pressure plate fitted. Ensure you have the later, post '72, design pressure plate #0710132 (can be purchased from our on-line store) 6) You may have the incorrect quantity and grade of oil. See fuel & oil tips. 7) Your clutch may slip if the friction plates are worn excessively. Stormer friction plates should measure 0.090" thick. The wear limit is 0.002" We have new replacement plates with fibre friction material available #40906 8) Your clutch may slip if the diaphragm spring is weak. Replacing the diaphragm spring can be also compensate for worn friction plates. We offer an up rated spring kit (#USK) which is 25% stronger than the original spring and has a self centering effect due to a re-designed bearing adaptor. If your casings are out of alignment your clutch may "drag". Our up rated spring Kit will help solve this problem too. USK Up Rated Spring Kit, fits Starmaker and Stormer. Note: Starmaker clutch plates are not interchangeable with Stormer clutch plates. It is possible replace your complete Starmaker clutch for the later Stormer clutch. Please contact us for a price. You can find clutch cables, levers, the Up-rated Spring Kit #USK, and the late type pressure plate #0710132 in our web shop. Use the search facility to locate the items.




How do I cure a misfire? or I have no spark


Misfire Diagnosis and Cure
1) Start at the top. Check the spark plug cap and replace the spark plug first of all.
2) Disconnect any kill switch if fitted. If you need to kill the engine in an emergency, hold a strong piece of rag firmly over the muffler outlet and stifle the engine.
3) Unscrew the plug cap, and check to see if the spark will jump 6mm from the end of the wire to earth when cranking the engine over by hand. If it does, check the condition of the plug cap, replace and try again. If the spark will not jump the gap, you have a problem. Read on....
4) Check the H.T. lead and L.T. connections at the coil for frayed wires & poor connections.
5) Check to see if the points gap is correct (.018"), also check to see if the points are chipped, contaminated with dirt/oil/corrosion or if the contact faces have become loose. Replace if suspect. Part No. 869517.
6) Check to see if the copper strip joining the rocker arm to the base plate, is shorting out to earth also check if the contact breaker cover is not touching the contacts or copper strip when it is screwed into place. Try the bike with the points cover off and on.
7) Check to see that the condenser has a really good earth. The early cotton reel type condensers are very prone to bad earthing.
8) If the points are sparking excessively, the condenser may be faulty. Replace if suspect. Part No. 31297FB.
9) Check to see that the ignition cam has been installed correctly (look for the direction arrow). Be careful if you try to remove the cam they are made from cast iron and are very brittle!
10) Check up and down movement on the crankshaft excessive play in the main bearings can cause "points bounce" and misfires at mid to top end running.
11) Check to see that the flywheel is tight on it's taper. If it has come loose, lap it back on with grinding paste, clean and use strong loc-tite on the taper. (don't use loc-tite on the threads) Tighten the nut to 100lb/ft.
12) Remove the flywheel and check to see if the L.T. lead to the points, has chafed through on the back of the flywheel. This is a common cause of misfires.
13) Check the condition of the connections on the stator. Some original stators suffer from coils working loose and poor joints, especially where the rivet passes through the L.T. tag.
14) Check the earth lead for bad joints and poor grounding.
15) Check the coil connections. The wire from the points goes to + (terminal 15)
Note: If the engine has been running for some time with the coil wired the wrong way round, the coil may be producing a weakened spark which will fail under compression. The spark will look nice and blue, but the engine will not start. This can be very misleading because the plug will appear to have a nice blue spark when you check it, the plug will be getting wet but the bike will not start. Replace the HT coil if in doubt.




Why has my small end bush worn out prematurely?


The most likely reason for your small end bush failing is inadequate lubrication or/and over- heating.
The Stormer small end bushes have a 10mm (.375") diameter oil hole drilled in the end of the rod. Make sure that the bush has not turned in the con-rod, closing off this oil hole.
We have been running our own bikes on Fuchs Silkolene Casterene R40 @ 32:1 for many years without problems. We can highly recommend this castor based oil to you.
If you are experiencing small end problems and are using a modern synthetic oil, don't forget that these modern oils are designed for use in engines where the temperature is maintained and controlled at a lower level by liquid cooling.
These oils are not going to offer you the same protection that a castor based oil can provide.
So, before you seek a complicated solution by fitting needle rollers..... check your oil. It may be as simple as that.
Make sure you are not over revving the engine, particularly if it is a 370 or 410. Keep the gearing on the tall side and make the engine pull hard.




My front forks leak oil and stick down, what can I do about this?


1) To solve the leaking forks problem check the condition of your forks to see that you have no stone chips in the stanchions that may have torn the seals. Note: Be sure to remove upstanding stone chips from the fork stanchions with a fine oil stone or 600 grade abrasive paper backed up on a steel rule or similar. Also, check for excessive wear in the bushes, particularly the top bushes. Pull on the front brake and rock the bike a small amount observing the front forks for lateral movement.Too much clearance here will cause the forks to loose contact with the oil seals under hard braking. The result will be oil leaking when the forks are compressed.The usual cure is to fit new top bushes. We have them available #0700077 (they will need reaming after fitting) We also have new stanchions available if required #0700063 To cure sticking forks, first check that the forks are not pinched in at the bottom. Loosen off the clamp bolts on the bottom of the fork legs and bounce the forks up and down to determine their best position on the axle. Clamp up tight when the best position is obtained. we suggest you remove the oil seals, packing washers and foam rubber wiper seals and replace this lot with our twin seal conversion kit. #TSCK. 2) The original 'wiper seals' cause the forks to 'stick' and do not really wok in the way they were intended. The twin seal kit offers double the oil wiping performance of the original setup. 3) Check the free length of the fork springs. The free length should be: 508mm (20") 4) Use 7.5 fl oz (220ml) of Pro RSF anti-foaming 15 Racing Suspension Fluid per leg to minimise fork "patter" and front end "washout" on hard packed fast corners. Caution: 1) Always check to see that the pins securing the damper rods to the bottom nuts are in good condition and have not worked loose. 2) Always check to see that the damper rod circlips are in place, and secure. When fitting these circlips, make sure the sharp side of the circlips are towards the outside. Check the fork damper rod retaining circlips on a regular basis. Put the bike on a stand, remove the front wheel and tug down on the fork legs vigarously.




Is there an easy way to replace the gearbox end cover?


How to fit the gearbox end cover, the easy way:
1) Ensure all the gears are assembled into the gearbox shell correctly and the quadrant assembly is assembled correctly into the end cover.
2) Stick the end cover gasket (#C11905) to the gearbox shell with non hardening jointing compound such as Wellseal, Hylomar Blue or Gold.
3) Stick the cam barrel bearing thrust washer (#27598) onto the gearbox shell bearing face with sticky grease, to hold it firmly in place during the assembly.
4) Rather than use the method of aligning timing marks as described in the Workshop Manual, it is easier to assemble the end cover when top gear is selected.
To time the gears correctly for assembly, think of the cam barrel and the gear change quadrant spindle as two meshing shafts. They rotate in opposite directions. So, rotate the cam barrel fully anti-clockwise. Then with the end cover in your hand (gear lever fitted) apply the thumb of your holding hand to the quadrant to exert some pressure, repeatedly down shift the gear lever to position the quadrant in the top gear position.
5) Carefully position the end cover and gently work it into place.
6) Insert two opposing screws lightly and test for all four gears.
7) If all is OK, insert the remaining screws and tighten diagonally and evenly.
8) Replenish the oil. Silkolene Medium Weight Gear Oil 85W 90.
Quantity: 1 imp. Pint (570ml)




What tips can you give me to improve my AJS Stormer?


Top Performance Tips From The Toolbox These tips are all used and proven on our own works bikes.
The differences these improvements make will transform your stock bike.

1) Fit Good tyres. Cheap tyres will most definitely not offer the same level of grip. Decent tyres will enable you to improve your riding skills and will boost your confidence.
2) Fit a decent muffler. A noisy bike is tiring to ride.
3) Fit our Serrated Foot peg wideners for a firmer, surer foot hold.
4) Fit a Gunnar Gasser twist grip. Medium quick action with the advantage of safely routing your throttle cable sideways out of the way of branches and bushes.
5) Improve your braking significantly by fitting our High Friction Brake Shoes.
6) How to get more power out of my 250 and stop it "gassing up" If you have good engineering skills do the following: Open out the transfer ports where the cylinder meets the crankcases as far as you can within the safe limits of the castings. You need as much volume here as you can get. Set the compression ratio to 10.5:1 and set the squish gap midway along the squish band to 1mm (0.040") Then you can install a 36mm or 38mm 2 stroke carburetter. Amal jetting guide: slide 2.5, MJ: 440, NJ: 108, Pilot: 20-25
7) Clean up the carburation and improve power by fitting an Amal Mk 2 carburetter. 34-38 for the 250 and 36-38 for the 370/410 depending upon engine state of tune. 32mm is a No No if you want optimum power.
8) Overhaul your ignition. Fit one of our improved stators #27851 for reliability.
9) Fit decent rear shocks for rear end control.
10) Fit our 1" extra thick seat with moulded foam for extra comfort.
11) Overhaul your front forks. Use pro, non foaming fork oil .
12) Use the correct tools. We can supply: flywheel / clutch strap wrench #0710061, diaphragm spring compressor #0710062, engine sprocket puller #0710060, ignition timing tool #0710057. Available form our on line shop.




How can I buy parts for my AJS Stormer?


You can buy parts from our web shop www.ajs-shop.co.uk or call us on +44 (0)1264 365 103 (9-5, Mon-Frid) or email us spares@ajsmotorcycles.co.uk with your enquiry.




Can I get a dating certificate that the DVLA will accept for registration purposes?


Yes, we can supply this.
Either submit your frame and engine number to us
or email us a clear, in focus, high resolution photo showing the complete left hand side of your bike. From this we can date it, as changes were made to the Stormers year on year from 1969 until the later FB-AJS models in the 1980's.
if you require a printed certificate, there is a charge for this service.
If you just want a date by email, we can do this free of charge.
Please email us here with your requirements. We'll get right back to you.




Can you date my Stormer?


Yes, we can supply this information.
Email your frame and engine number to us and also us a clear, in focus, high resolution photo showing the complete left hand side of your bike. From this we can date it, as changes were made to the Stormers year on year from 1969 until the later FB-AJS models in the 1980's.
if you require a printed certificate that the DVLA will accept, there is a charge for this service.
If you just want a date by email, we can do this free of charge.
Please email us here with your requirements. We'll get right back to you.




What are the main differences between a 250 Starmaker and a 250 Stormer engine?


All Stormer engine numbers begin with A250
Starmaker engines are designated 225H with the following variants:
757D Standard Scrambles with wide fins, wide ratio gearbox and twin Amal monobloc carburetters.
490E Road racer version of 757D but with close ratio gears and a tacho drive.
494E Scrambles, but with 6v direct lighting.

826E Scrambles, with single Amal monobloc carburetter.

827E Scrambles with single Amal monobloc carburetter and 6v direct lighting.

834E Road racer with close finned cylinder and head close ratio gears, tacho drive, outrigger contact breakers, and Amal 3GP2 carburetter.

865E as 834E but with 6v direct lighting.

871E trials engine, with wide ratio gears, and Villiers S.25 carburetter, but without lighting

972E Sports roadster, with single Amal carburetter and 12v rectified lighting.
091F Special, with single Amal monobloc carburetter, but without clutch, gearbox and primary drive.

131F Trials engine with 6v direct lighting.

Visually the Starmaker and Stormer emgines look very similar, but in summary the following are the main items of difference:

  1. The Stormer piston has a shorter back and has shrouded rings covering the ring pegs. The Starmaker has butted rings and a longer back.
  2. The Stormer crankshaft is wider due to the big end having thrust washers either side of the crank pin, where the Starmaker crank does not have thrust washers.
  3. The Stormer con-rod has a 3/8” diameter oil hole in the top, the Starmaker rod has a wide (and weaker) oil slot. (fine for trail and trials use)
  4. The Stormer has reinforced engine mounting point on the crankcases.
  5. The Stormer crankcases are wider inside to accept the wider crankshaft (see point 2)
  6. The Stormer has reinforced ribs on the gearbox to frame mounting.
  7. The Stormer has a removable cylinder liner, the Starmaker line is “cast in”
  8. The Stormer may have close ratio gear ratios, the Starmaker would have had wide ratio, trials or road race gears.
  9. The Stormer has a lighter and stronger magneto flywheel than a Starmaker.
  10. The Stormer has different clutch friction plates to those of a Starmaker. The Starmaker plated have a riveted centre fitted to them.
  11. The Stormer has a larger diameter clutch centre.
  12. The Stormer has the spacing of the front chain case screws spaced closer together to give better clearance inside for the primary chain. The Starmaker inner chain case has mounting hole next to the gearbox sprocket, the Stormer does not have this hole. Therefore, they do not interchange.
  13. The Stormer has a longer clutch operating pin.
  14. The Stormer has an improved clutch pressure plate (not diaphragm spring)
  15. The Stormer has an improved gear change quadrant.
  16. The Stormer has an improved gear change cam barrel.
  17. The Stormer inner magneto case has a sealing O-ring against the crankcase; the Starmaker casing does not have this O ring.
  18. The Stormer does not have an exhaust gasket because the exhaust is mounted in a push- fit sleeve. The Starmaker exhaust is clamped to the cylinder and needs a gasket.




What does F-B AJS stand for?


The F-B prefix to the AJS initials refers to the late Fluff Brown. Fluff used this prefix on many of the bikes he produced after buying the Stormer stock from Villiers after the Norton Villiers group went bust. Fluff continued to develop the Stormer from 1974 until the ealy 80's with such enhancements as: Amal Mk 2 carburetters, long travel suspension, snake type exhaust systems, Girling gas shocks, Stadium plastic mudguards, Motoplat electronic ignition, replacement frames, and many more refinements which kept the Stormer based machines modern and a viable option for clubman racers. Many young riders enjoyed sucesses on FB-AJS machines.




Why does my rear brake judder, shudder and vibrate badly?


When you press the rear brake pedal any you feel a strong vibration or shudder through the foot pedal it is probably because the rear brake torque arm has come loose. Check the bolts quite urgently. Failure to do so can cause the brake plate to fracture or the brake torque arm to fail. Remove and Re fit the bolts using Loc-Tite Threadlocking Compound and spring washers.




How do I wire up the points and stator?





What is the best way to start my AJS Stormer?


Starting a large capacity two stroke can be daunting. Follow these steps to make it easier and safer for yourself.

Make sure the bike is in good mechanical condition.

Make sure the contact points are clean and adjusted correctly.

Make sure the ignition timing is set correctly.

Make sure the carburetter is set up correctly and in good condition.

Correct pilot air screw setting helps starting.

Firstly, put on your MX boots to protect yourself from kick-back.
Position yourself and the bike on firm level ground.


If the engine is cold, tickle the carburetter or apply the cold start device.

Stand on the right side of the bike.

Hold the right handle bar in your right hand, Hold under the seat firmly with your left hand, and kick the kickstart lever with your right foot.

Make sure the kickstart/footrest are modified so that the kickstart clears the footrest boss, enabling a full swing. Make sure you are wearing a MX boot.
If the engine tries to kick back constantly, check the ignition timing and retard the ignition timing it a little if necessary.
A well set up bike, and a little practise, should start within 3-4 kicks each time.





Model: Y4, Y4 MK,2 250 Stormer 1968 - 1974 

Standard Technical Data for MX use, without "Works Tuning"

 

Engine

Bore: 68mm

Stroke: 68mm

Capacity: 247cc

Compression Ratio: 11:1 

Port Timings: Exhaust: 180 deg, Transfer: 135 deg, Inlet: 152 deg.

Ignition Timing At Piston: 2.5mm (.1 ins.) At Crankshaft: 20 - 22 deg.

Contact Breaker Gap: .38mm (0.015 ins.) 

Spark Plug NGK B8ES - Champion N3 Plug 

Gap: .635mm (.025 ins.) 

 

Transmission 

Engine Sprocket: 20T 

Clutch Sprocket: 43T 

Gearbox Sprocket: (520) 13T 

Rear Sprocket: (520) 61T 

Gear Ratios (Close Ratio): 1st - 2.00 2nd - 1.51 3rd - 1.25 Top - 1.00

 

Carburetter 

The Amal Mk1 32mm "932" was fitted as standard, however we recommend fitting the Amal Mk2, 34mm for standard Stormer 250 engines and Mk2 38mm for "Works Tuned" engines. 

(Check for eligibility with your club). 

 

Amal 932 Settings:

Throttle valve: 3 Main Jet:

280 Needle Jet: 107 Needle position:

Middle Pilot Jet: 20

 

Capacities

Fuel Tank: 1Imp Gallon, 2.4 US Gallons, 9L.

Gearbox: 1pint, 20 fl oz, 

Primary Chaincase: 0.57 pint, 7.5fl oz, 210cc 

Front forks (each leg): 0.57 pint, 7.5fl oz, 210cc 

 

Lubricant Types (recommended)

Fuel Mix: Silkolene Casterene R40 @ 32:1

Gearbox: Silkolene Medium Weight Gear Oil,

E.P.90 Primary 

Chaincase: Silkolene Light Weight Gear Oil sae 10/40 75w or Silkolene 10w Front Fork Oil If using our red dot primary chains #27799B.

Rear Chain: Silkolene Chain Lube.

 

Other data

Steering Head Angle: 30 deg.

Fork Trail: 5.15ins.

Pistons Piston Skirt Diameters: 67.913mm/67.887mm (2.6738/2.6727 ins.)

Piston Clearance in bore: .076mm/.89mm (.0025/.003 ins.)

Ring Gap: .178mm/0.305mm (.007/.012 ins.)

Con-Rod length, centers: 126.97mm/127.025mm (4.999/5.001 ins.)

Small End Bush Bore:17.47mm (.675 ins.)

Model Y5, Y50 370, 370 Stormer

1970 - 1974

Standard Technical Data for MX use without "Works Tuning"

 

Engine

Bore: 83mm

Stroke: 68mm

Capacity: 368cc

Compression Ratio: 11:1

Port Timings Exhaust: 180 deg, Transfer: 130 deg, Inlet: 170 deg.

Ignition Timing At Piston: 2.5mm (.1 ins.) At Crankshaft: 20 - 22 deg.

Contact Breaker Gap: .38mm (0.015 ins.)

Spark Plug NGK B8ES - Champion N3 Plug Gap: .635mm (.025 ins.)

 

Transmission

Factory set-up. Engine Sprocket: 24T

Clutch Sprocket: 40T

(we use Engine Sprocket: 20T

Clutch Sprocket: 43T)

Gearbox Sprocket: (520) 12T

Rear Sprocket: (520) 65T

Gear Ratios - Wide Ratio. (We use the 250 Transmission set-up and a C.R. gearbox) 1st - 2.52 2nd - 1.66 3rd - 1.25 Top - 1.00

 

Carburetter

The Amal Mk1 34mm "1034" was fitted as standard, however we recommend fitting the Amal Mk2, 36mm for standard Stormer 370 engines and Mk2 38mm for "Works Tuned" engines. (Check for eligibility with your club).

 

Amal 1034 Settings:

Throttle valve: 2.5

Main Jet: 370 - 410

Needle Jet: 108

Needle position: middle

Pilot Jet: 25

 

Capacities

Fuel Tank: 1Imp Gallon, 2.4 US Gallons, 9L.

Gearbox: 1pint, 20 fl oz,

Primary Chaincase: 0.57 pint, 7.5fl oz, 210cc

Front forks (each leg): 0.57 pint, 7.5fl oz, 210cc

 

Lubricant Types (recommended)

Fuel Mix: Silkolene Casterene R40 @ 32:1

Gearbox: Silkolene Medium Weight Gear Oil, E.P.90

Primary Chaincase: Silkolene Light Weight Gear Oil sae 10/40 75w or Silkolene 10w Front Fork Oil If using our red dot primary chains #27799B.

Rear Chain: Silkolene Chain Lube. 

 

Other data

Steering Head Angle: 30 deg.

Fork Trail: 5.15ins.

Pistons Piston Clearance in bore: see note

Piston length at the rear: 73mm

Ring Gap: .178mm/0.305mm (.007/.012 ins.)

Con-Rod length, centers: 26.97mm/127.025mm (4.999/5.001 ins.)

Small End Bush Bore:17.47mm (.675 ins.)

Model Y51, 410, 410 GP, 410 Stormer
1971-1974
Standard Technical Data for MX use without "Works Tuning"


Engine 
Bore: 83mm
Stroke: 74mm
Capacity: 400cc
Compression Ratio: 11:1
Port Timings: Exhaust: 180 deg, Transfer: 130 deg, Inlet: 154 deg.
Ignition Timing At Piston: .125 ins/3.2mm At crankshaft: 20-22 deg. 
Contact Breaker Gap: .38mm (0.015 ins.)
Spark Plug NGK B8ES - Champion N3 (unless a 370 conversion, in which case a short reach plug will be used such as NGK8HS)
Plug Gap: .635mm (.025 ins.)

Transmission 
Engine Sprocket: 24T 
Clutch Sprocket: 40T 
Gearbox Sprocket: (520) 12T 
Rear Sprocket: (520) 65T 
Gear Ratios-Wide Ratio. (The C.R. gearbox may be used. See 250 data.) 1st - 2.52 2nd - 1.66 3rd - 1.25 Top - 1.00 

Carburetter
The Amal Mk1 34mm "1034" was fitted as standard, however we recommend fitting the Amal Mk2, 38mm for standard Stormer 410 engines and "Works Tuned" engines.

Amal 1034 Settings:
Throttle valve: 2.5 
Main Jet: 370 - 410 
Needle Jet: 108 
Needle position: middle 
Pilot Jet: 25 

Capacities
Fuel Tank: 1Imp Gallon, 2.4 US Gallons, 9L.
Gearbox: 1pint, 20 fl oz, 210cc 
Primary Chaincase: 0.57 pint, 7.5fl oz, 210cc 
Front forks (each leg): 0.57 pint, 7.5fl oz, 210cc

Lubricant Types (recommended)
Fuel Mix: Silkolene Casterene R40 @ 32:1
Gearbox: Silkolene Medium Weight Gear Oil, E.P.90 
Primary Chaincase: Silkolene Light Weight Gear Oil sae 10/40 75w or Silkolene 10w Front Fork Oil If using our red dot primary chains #27799B.
Rear Chain: Silkolene Chain Lube.

Other data 
Steering Head Angle: 30 deg.
Fork Trail: 5.15ins.
Pistons Piston Clearance in bore: see note
Piston length at the rear: 75mm
Ring Gap: .178mm/0.305mm (.007/.012 ins.)
Con-Rod length, centers: 139.67mm/139.725mm (5.499/5.501 ins.)
Small End Bush Bore:17.47mm (.675 ins.)

 

Errors and omissions expected. For further hep contact us.
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How to set up, re-jet and pretty much everything else you might want to know about AMAL carburetters, download the PDF information document.

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*SRP Prices include VAT, delivery to the dealer (standard UK regions), Pre Delivery Inspection, full build up, number plate and 12/24 month warranty (see warranty terms & conditions). 
Prices may vary according to dealer locations and dealer packages and offers. Government first vehicle registration tax and vehicle excise duty are not included and will be added at the current rate.

Specifications and prices are subject to change without prior notice. All photographs are for representation purposes only. Actual model details may be different to those depicted. AJS Motorcycles Ltd. reserves the right to alter specifications and prices without notice. E&OE All dimensions are nominal.

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