The Armstrong MT500 & MT350
This article was written by Mike Forrester of Motorcycle.co.uk and has information for the UK market on ex-Army Armstrong (and Harley-badged) MT500 and MT350 motorcycles using the Rotax motor. Mostly popular in the UK, there are some in the US/Canadian market, and a small following in other places.
After a basic Rotax-engined design had been created in Italy, and been passed around SWM & Bombardier - the Armstrong-CCM company started supplying MT500 bikes to the UK army in 1984. Around 1987, the military motorcycle production was sold to Harley-Davidson, and they were built by H-D.
The MT350 appeared in 1993 (as a development of the M50, official designation of the electric-start MT500), and continued until 2000.
A small number of electric-start MT500s are around. Never supplied to the British Army, but believed to have been used by the Jordanian and Canadian armies. Ex-army, these are probably badged M50. Some electric-start civilian MT500s exist in the UK market. This may have followed an attempt by Armstrong to build a Police-spec motorcycle, though we don't think the Police ever took them on. May be white, may have been 300 sold, some may be 560cc.
By 2000, the UK Army had moved on to Honda XR250s, Kawasaki KLRs, and are currently prototyping diesel bikes in line with the single-fuel policy.
|Major differences MT500 / MT350|
500cc 4-valve Rotax motor.
Drum front brake
Pannier frames both sides at rear.
(Harley-Davidson on side panels on this one.
350cc 4-valve Rotax motor.
Electric and kickstart
Disk front brake
Panniers at front, 'gun-carrier-case' sometimes fitted to right rear.
Thinking of Getting One
They are heavy for an off-road bike. They are not particularly fast. The left-hand kickstart of the 500 is an acquired art.
Still reading :) ..... OK
They are reliable when sorted. They were built for Squaddies to drop without breaking. There is no chrome to go rusty.
They make great commuter bikes - quick handling, with that indispensable urban 'I don't care if I scratch it on your Mercedes' attitude.
They are quite competent off-road. Not competitive enough for MotoX, but some Enduro riders are happy to accept their extra weight in return for rugged strength. As a Green Lane bike, they are perfect.
(If you want something more 'performance', try an ex-army Honda XR250, the excellent XR250 with less chrome and a larger 'Baja' tank.)
Additional screen, hand-guards, MT350 front end....
Viewing a Prospective Purchase
History is everything - and usually impossible to determine.
Buying direct ex-army, you will be very lucky to get any history. Even the mileage on the speedometer cannot be be relied on. You have no way of knowing what it has done, where it has been, or how well it has been maintained.
You can sometimes guess at a history. UK Army bikes with gloss, rather than matt, green paint have traditionally been for 'ceremonial duties', so may not have been thrashed in-theatre. Bikes in sand colour are probably ex-Special Forces. But that doesn't tell you anything. A bike with low miles may have sat in a hanger all its life and never been used. Or it may have had its motor swapped with a broken one. Some are rumoured to be released from the Army without ever being started up - and with preservative fluid in the engine, rather than oil. Or it may have come back from somewhere with serious engine damage, then sat around not being fixed.
A recent consignment of released crated MT350 engines seems to have been 'engines removed in service', with various breakages and component failures. (They were sold 'as-is', part-dismantled, with absolutely no guarantees or information, the company concerned was not trying to fool anybody.)
Buying direct ex-Army - at auction - you are taking a big chance. If you can start it up, that gives you some indication. Most often you are buying blind.
From an Army Surplus Dealer
There are Dealers who buy at auction from the Armed Forces, check the bike over, then sell to you and I. Price has to be higher, to cover their time and work, and give you some warranty. They will also register the bike for you; service it, and no doubt sell you indicator bulbs....
Buying from a Dealer like this will get you a good bike. Force Motorcycles are probably the best known, and are very well respected in MT circles. Withams-SV are principally an actioneer, but they will sell individual bikes direct to the public. They may let you start it up and ride up and down in their yard, but that is all. LMS Ltd, Lichfield are big army surplus dealers. Also look at Disposal Services Agency, 'an Executive Agency of the MoD'.
You pays your money and takes your chance.
- Bidding at auction - usually buying blind
- Direct from a Disposal Company - pick over a few, choose one you think looks OK
- From a Dealer - its been checked over, you get a warranty, there's backup if it goes wrong
There are many MTs now in private hands, so of course there are a number of bikes on the private market. Check whether they have been using the bike, not trying to offload an un-registered dog they got at auction ! If they have been using the bike, it will have been road-registered, and it should have had any problems sorted out. You will very often find that owners are enthusiasts, who will have done the sensible modificatins to make them more reliable (see below).
Buying privately is probably the best way into MT ownership. Or from a specialist like Force if you want some warranty and backup. I would not recommend the newcomer to these bikes to dive head first into buying at auction - especially when you realise that private prices are often less than auction prices.
Where to buy online
Usually one or two on eBay. I'd want to go and check it out before bidding, particularly for a bike like the Armstrong, which can be well abused and still look 'normal' in the photos. They go for about the same money as a private sale.
You can also try milweb.net, sometimes an Armstrong pops up there among the Harley WL45s and Urals.
And there's the MSN Group. Quite aside from the vast technical knowledge in the group, this is the best place to get a good bike in the UK. Group members are in the habit of posting bikes for sale here. Or you could post a wanted message. Buying through this group is much more likely to get something well maintained, and MT500s sold through here have very often had the good mods done.
Private sales of sound useable MT500s start around £700. This will get you a good running MT500 with MOT. If it has had sensible mods done (at least a proper carb), perhaps £850. For this price it may have scuffed paint, some parts may be painted matt black, etc.
There are very few 500s in pristine condition. If it has the MT350 front end fitted, perhaps a dual seat conversion, this makes it more desirable, and ups the price a little bit. Those that have been bought as projects, and rebuilt well with new parts, panels, and repainted, may be worth up to £1500. Immaculate concours examples are very rare. If you get one from Force Motorcycles or similar, be happy to pay more for peace of mind.
Private sales of sound useable MT350s start around £1250. This will get you a good running MT350 with MOT. There are few mods that need to be done to improve the 350, so price is based more on straight-forward condition than the 500s. You need to be prepared to pay more for one with the very useful front panniers, and with the gun-carrier rear 'pannier' if you like its style (and really want to frighten Mercedes drivers :). Good MT350s can easily reach £2000, more for a guaranteed, warrantied one from a specialist dealer.
The relatively higher price of the 350s over the 500s is down to a few factors
- 350s have electric start - this is #1 reason to prefer the 350 over the 500
- 350s have a disk front brake - the front drum is a weak point on the 500. For urban commuting, it makes a big difference.
- 350s are newer, so might be in better overall condition - though this is not a big issue
Army bikes have army registrations. When they are released to the public, this is removed, and they are sold with 'de-mob papers'. This Army-Release paperwork is effectively your 'Registration Papers'.
To get it on the road, you first need an MOT. Your local tester will do this using the frame number as its identity. (This is for the UK, other countries will vary.)
You then take all the paperwork you have, the MOT, your insurance certificate, and proof of your identity (explained here) to your Local Vehicle Registration Office, who will speak with DVLA's computer, issue you with a registration number, and a tax disk for 12 months. You pay the LVRO the Registration Fee (currently £38) and 12 months road tax. They will not usually want to inspect the bike, though this may change in line with various DVLA / VRO changes currently working through about SVAs and re-registering (usually insurance write-off) vehicles, and 2003 EU regulations about 'registering bikes not homologated under current import restrictions'.
Then you take proof of your identity and the LVRO paperwork to your local motor factor, have a number plate made up, and away you go.
Registration is not a difficult process. It is a bit of hassle having to go to your local VRO - which may not be 'local' to you - but they are helpful friendly people, and there is no reason for them to refuse you a registration as long as your paperwork is in order.
PS You should be issued with an age-related number. I.e. a 1985 bike will get a C-registration. You should not be offered a Q-registration, since you can clearly demonstrate 'Year of Manufacture' to be 1985 from the Army Papers.
Absolutely #1 check. Is it straight ? I don't know how many may have been dropped out of helicopters - maybe that is an urban myth - but some of them will have had a very hard life. It would be no surprise to see one with a bent frame.
It should have a substantial rack fitted to the rear (not the pannier frames - the rack itself). Squint along this at the line of the bike. These racks are strong and very securely mounted. If the bike has been dropped heavily, the rack may have taken the hit, and it will have twisted the rear subframe. This in itself is not a problem, but it prompts you to look much more closely elsewhere for cracked welds, twisted sections, bent forks, etc.
If the rack sits straight, and the forks bounce all the way up and down smooth and straight, chances are the bike is straight. Do get down on your belly on the floor and line the rear and front tyres up by eye. Any twisting of the frame should be obvious.
Check the exhaust's silencer, from where it joins the headers above the swingarm spindle. It is unlikely to have been damaged in a fall - it is well tucked in - but many have rusted internally. If there is rust coming through from the inside - and any under-paint rust you can see is coming from inside - you will be replacing it soon. Grab it between your hands and squeeze hard, any crunching noises spell doom. Stainless steel replacements are available.
A 500's engine may be difficult to start, this is not in itself a problem (see below). Once started and warmed up, listen carefully. It should have whirring sounds from various components, perhaps some tappet noise, but it should not knock anywhere. The engine is in contrast to the rest of the bike, it is a precisely engineered jewel of a motor. It should be smooth and sweet. Any knocks, graunches, or nasty metallic noises are wrong.
If the clutch squeels alarmingly as you pull off, don't worry. 500s do it more than 350s, some 500s more than others. Synthetic oil made mine worse. As long as take-up is smooth 'They all do that, Sir'. A scrape/graunch is something else, of course, and probably indicates the clutch is loose on its shaft and rubbing the inside of the casing under acceleration.
Front brakes are either 'is there anything there' (500), or 'stand on its nose' (350). Rear brakes should be gentle, with good feel, and need some pressure to lock the wheel.
Everything else about the bike should be 'normal', in a soft, comfortable off-road bike kind of a way. It should be smooth with you sitting down, and quite 'flickable' standing up gripping the tank with your knees.
Get it into 3rd or 4th at low revs and snap open the throttle. 99% of Armstrongs will cough and hesitate, then lunge forward. If it pulls smoothly immediately, congratulate the owner on their carburettor settings. If not, try again, opening the throttle more progressively. It should pull well and strongly all the way to the red-line*. If it still hesitates, see 'Carburettors' below.
(* They are not fitted with rev-counters, so I know there is no redline.
Judge it by ear.
If you want to know if it is revving high enough, top gear should pull you to 80-85mph before it runs out of puff.)
All other checks and tests are the same as for any bike. A good Armstrong will be smooth, with a 'pulsing' engine vibration and well-balanced, predictable handling.
Starting a 500
MT350 owners can get all superior and smug at this point. Prospective owners of MT500s need to know that this is the Achilles Heel of an otherwise great bike.
Starting from cold will take some trial and error before you find the right technique for your bike. They all seem to respond best to different methods, but here is the generally accepted starting point. Fuel on, choke full on. Decompressor in, 1 firm kick over. Up to 'White in the window', 1/8th throttle, and one big committed swing. If it doesn't start, go to half choke, 'White in the window' and swing again. If it doesn't start, it is probably now flooded. Clear it using the decompressor and try again.
Most of us kick it off the bike using our right leg. If you are young and fit, you could practice the art and you may be able to learn how to get it going with your left leg. Once the engine is warm, they start easier, and a desperate lunge with the left leg will often get it going again.
Oh, that damned left-hand kickstart. You only have to stall it once at the lights - frantically kick a couple times, realise you can't, struggle to find neutral, get off, and slink to the side of the road going bright red under your helmet to kick it alive again - to know true embarrassment. And unless the carburation is spot on, and the engine is warm, this will happen to you.
It is believed that a very small number of Canadian (H-D badged M50 ?) 500s had electric start, and Rotax 500 engines used by MZ and others had electric start. And in principle, a mix of 350 bottom end and 500 top end is possible. The difficulty seems to be that the 500's frame needs modification to clear the starter, and the frame at that point is also the oil tank.
Starting a 350 should not be a problem. Its a smaller engine to kick over in the first place. Even if you like to have a couple of kicks to turn it over when it is cold (kinder to the battery and starter), you do not have the 'stalling it at the lights' embarrassment situation.
Good Mods and Bits to Have
MT350s don't need much modification. We have heard that a 500cc conversion is possible, using the MT500 top end.
It is up to you whether you want the forward-mounted panniers and frames. They are more useful than they seem if you need to carry heavy stuff. The rear gun-carrier box is said to be useful for nipping out for the Sunday Papers, which fit neatly in there.
MT350s should come with bark-busters - a loop like an overgrown knuckle-duster from the end of the bars. They offer no weather protection, but do have a 'Mercedes-worrying' ability, and are obviously useful offroad.
Both the MT350 and MT500 could usefully be fitted with proper handguards: The 350 for weather-protection, the 500 because it has nothing as standard.
500s really need a better carburettor. The original is widely regarded as difficult to keep in tune, gives less power, and uses more fuel than a more modern replacement. Budget £200 for a Mikuni replacement, and expect to be fiddling with different jets for a while to get the mixture spot-on. If you buy one already converted, quiz the owner about which jets they used. Often, one will be fitted with whatever jets it came with, offering little improvement over standard. I can assure you from experience that you can find quite a few more horsepower, and a lot more smooth running, from careful setup. Even if the carb was supplied by a Rotax specialist with 'the right jetting', you do want to fine-tune it yourself.
500s also need a better front brake. You can strip the original to make sure it is working as well as it should. Or you could fit a 350 front end (complete front-end, including stanchions and yokes). For what looks like a small single-disk, this gives some serious front-wheel-locking action!
|Dual seat conversions are readily available and bolt straight
on. Footpegs mount either to frame (may need some drilling) or
bolt to swingarm. The rear rack needs to be removed or shortened.
If the rack is kept, the side pannier frames can also be kept,
but they seriously limit pillion leg clearance, and will pose
a threat to the pillion's ankles if swingarm-type footpegs are
Here is a comparison of the two, showing where you need to modify the rack - cut just in front of the indicator mounts.
(Non-standard indicator fitment on this bike. Its actually the fronts mounted on the rear mudguard. Indicators normally bolt into the holes in the side of the rack - and dangle quite a long way out.)
|The standard tank caps openings are big and wide - perhaps for filling in the field from jerry cans ? - and this seems to have resulted in having a cap that does not seal well. Seepage can be helped by ensuring that the cap vent is clear and a tube vents from it to air down in the steering head somewhere. The only complete cure is an after-market tank - which could also usefully increase fuel capacity if you want to do some adventure touring down Western Sahara or wherever.|
If you like a screen, I can recommend the 'National Cycle Deflector' handlebar mounted screen - about £60 from M & P and others. Needs some careful grinding & filing to square off the bottom to fit neatly over the MT nacelle. Keeps the wind and rain blast off you, while being small and neat enough not to get in the way even in quite radical off-road play. (And has quick-release mountings just in case you go over the bars)
Working On Them
#1 Maintenance Tip - Get a proper Army manual. Lovely line drawing exploded diagrams, clear explanations of procedures. A good previous owner will have got one of these already. If you need one, ask the MT Riders Club Forum.
If you buy one of these bikes, you probably know how to get your hands dirty, so I'll just say get an Army manual, and work it out for yourself. There are no particular tricks you need to learn for either the 500 or 350.
- Use mineral oil, synthetic makes the clutch snatch.
- Be careful not to strip engine bolts, the casings are quite soft.
- Check when the cambelt was last changed - if in any doubt, replace.
- The spark plug is awkward to reach, your generic socket and extension may not get in there and you may need to buy a new thin-walled plug spanner to get at it.
- Electrics are simple, but components can be unreliable.
- Regulator/Rectifiers (bolted to the top of the airbox) fail. If your battery needs topping up regularly, you are probably boiling it with over-charging from a dead regulator. Replacement is easy, with OEM from a specialist, or that old bodger's standby, the Honda Superdream unit.
- I have heard of flasher units failing regularly. If you replace one with a cheapie from the local Accessory Shop, don't expect it to last long. If you know of a proper ruggedized, bullet-proof solution - let me know before mine goes again ;)
- Check the balance weights on the wheels. They are usually lumps of metal clamped round a spoke, they work lose and disappear. They are needed to balance the significant weight of the tyre-clamps which should be fitted. If one does get lost, they are not widely available. Easiest fix is to fit another tyre-clamp opposite the original, and then have balanced with stick-on lead bits. Or remove the tyre-clamp.
Temporarily filed here:
Here is the MT500 wiring diagram (its a big file, sorry).
And the listing of what the numbers on that wiring diagram refer to.
There was discussion a while ago the old MSN Group, and IrishBiker seems to have managed to gather quite a few. Check the MT Riders Club - the new home of the MSN Group - who may still list the link and details.
References and interesting reading
A short history of the MT500 / MT350
The story of Snarley, a welsh persons take on the MT350
One man's story of extracting more power from an MT500
Force Motorcycles brief synopsis of MT350 including original specs.
Force Motorcycles brief synopsis of MT500, including original specs.
In Holland, try Grouenwoud
There are a few other resources out there, though not many, since these were never sold in high numbers. See in the text above or your favourite Search Engine - good search terms are MT500 MT350 M50 Rotax.
This article is copyright of Mike Forrester, who runs the excellent motorcyclist