Bright green was the colour someone had painted the GN400. This was supposed to be an unlucky hue but it just made me want to throw up. I stuck with it for a whole week after buying the bike. Dulux's finest matt black was brushed on which helped hide the mundane overall appearance.
The GN looks and feels tiny for a 400cc OHC single. An impression submerged when I'd kicked the engine into life. A roar out of the degutted silenced and a bustle of vibration. The engine has no balancer and shook in the frame like a Norton Commando!
This was because the front engine mount was loose. Some chisel and hammer work revealed that the bolt had stripped its thread. One nut and bolt later saw a much more stable engine. The vibes always gave an edge to the machine. After three or four months I no longer noticed the trembling. One pillion reckoned that the engine was about to blow up. He wasn't too amused to have his feet buzzed off the pillion pegs and received a burn on his ankle on the right-hand side. The exhaust like the engine ran very hot!
I was quite pleased with the lack of pillion comfort. It discouraged people from asking for lifts - the marginal acceleration was greatly diminished by the presence of too much mass. Performance was never wild even when solo. The ton could occasionally be put on the clock but 90mph was more normal.
Shortly after purchase the swinging arm bearings went. With 31000 miles done. The rear shocks were also mushy. Quite likely to have the rear tyre hitting the rear mudguard. It may have been this that caused it to rot or just poor chrome. The swinging arm looked like it was sourced from a 125 and had a spindle that was corroded in solidly.
By the time the spindle was extracted the whole lot was ruined. An interesting afternoon was spent sorting through the local breaker's boxes of bit. I even found some reasonable swinging arm bearings. A pair of Koni shocks and newish mudguard were also acquired. The whole lot cost £40.
The rear end felt much more solid but the front felt even looser. Weeping seals and pitted forks were revealed when I peeled back the gaiters. I was thankful that there was only 325lbs to control. The bike was narrow and the seat height low. Bumpy bends tried to throw the GN way off line but the wide, high handlebars gave easy control.
I left the front forks alone for about 6000 miles. Then they were stripped and rebuilt with new bushes and seals. The pits in the forks were filled with Araldite and smoothed down once it'd had a day to set. A well know bodge that works for many thousands of miles!
I couldn't in all honesty say that the stability was transformed but it was never dangerous enough to throw me off the road. After this repair there followed six months of reasonable summer weather and 9000 miles of trouble free riding. The GN was as simple and easy to service as a CG125, although it gave about half the economy. 60 to 65mpg was the best I could achieve.
Then the horrors started. I came out to the bike one autumn morning to find all systems dead. A flat battery! The GN reluctantly started on the kickstart so it wasn't the end of the world. Halfway to work the fuse blew. I narrowly avoided being run down by the rest of the traffic. The GN was always easy to swing around cars. Thank God!
There followed the usual Suzuki electrical scenario! Ever bigger fuses were fitted until only a nail would suffice. By the time I stripped all the rotted wiring out both the alternator and regulator had to be replaced. Used items from a breaker were bought mail order. I didn't have much choice as GN400s are rather rare.
The winter was closing in by the time the Suzuki was back on the road. Cold weather made starting a six to ten kick affair. A newish coil reduced that by half. There was also a tendency to cut out at low revs. It'd happened a few times in the summer but occurred several times every day during the winter. I ended up with the tickover above 2000 revs. The spark plug was replaced every month to keep the engine clean running during the worst of the weather.
The finish became terrible because it was too cold to spend time cleaning the bike. Rust on the guards, spokes, exhaust and forks became half an inch deep! The whole engine went white with the corrosion. Paint fell off the frame and petrol tank. Even the rack rusted through. The top box and half the rack were thrown off the back. A car mangled its front end over the debris. I stopped to see what I could salvage (riding these kind of bikes as commuters makes you mean to the point of stupidity) - the car driver decided to take a few right hooks at me. He stopped when he cracked his knuckles on my helmet! I was groggy for half an hour but it inspired me to pull the bike into the house for a thorough cleaning session. The way it was going I'd end up with the frame corroding all the way through.
As winter turned into spring and I began to thaw out, the back drum seized on solid. The shoes were worn down to the rivets causing the brake to over-cam and lock on permanently. I tried to kick it free but no hope of such an easy escape. I had to pull the whole wheel out and then prise the brake apart.
No sooner had I fixed that than the clutch began to slip. The side casing's screws were all permanently corroded into the crankcases. Most broke off. I had to drill the remaining studs out and redo the threads. What should've been an half hour job took a whole weekend. The pattern plates also needed some filing to make them fit.
Still, the bike ran with nothing more than 1500 mile service sessions and consumable replacements - tyres about 15000 miles, chain about 10,000 miles and the front pads (in an indifferent disc) about 15000 miles. Not an expensive bike to keep on the road.
With 55000 miles on the clock oil started spewing out of the cylinder gasket and it'd only sniff at 80mph on very long roads. I feared the worst but a valve regrind and new gaskets did the trick. The camchain looked good and the engine was as easy to work on as a CG125!
A summer tour around England followed. Pushed the bike to its limits on the odd section of motorway. The primary vibes could work up to a furious pitch at 95mph! I'd joined the AA just in case there was a breakdown but didn't have to call on their services. With a restrained right hand touring was well within the GN's capabilities.
The day after coming home from the tour the bike refused to start. I checked everything I could think of. The spark was vivid and the smell of petrol strong. The engine made grumbling noises but refused to start. I tried a new spark plug but no good. It was only when I took the carb off that the cause was revealed. A cracked manifold - either age or vibration. I patched it up and was back to three or four kick starting.
With 65000 miles under its wheels the end seemed nigh. I found it hard to believe that it would keep going for much longer. The major quibble at that time was the gearbox. It'd started out very precise only to end up as ornery as an ancient Honda. I could still wend my way through it with an excess of concentration and luck. Worn selectors were the cause but no chance of finding decent used bits before the motor started churning out smoke. Judging by the knocks and rattles there wasn't much life left. The clock read 65,840 miles.
I ended up fitting a GN250 motor. Performance's very similar, economy much better and vibes less. There's only 4000 miles on this motor so I'm set for the next few years riding. The GN400's quite a reasonable motorcycle and I can think of no reason not to buy a good example.
Martin Smith
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I like Suzuki's. Simple as that. The main reason's because they must have the toughest engines in the world. At least in the case of their four strokes. My all time favourite was a GS750 four that I took around the clock. Brilliant, never let me down, etc. The past few years have been hard going financially, I've had to go down market. The previous mount, a much modded GS400 twin. I sold that for twice what I paid for it, after 30,000 miles of fun.
I knew some of the history of the GN400 that I acquired next. Basically, a couple of mature owners, only used on dry days. Left the bike in exceptionally good nick for a ten year old, 17000 miler. At £300 it was too good a deal to miss. Even if its 27hp thumper engine wasn't the thing of legends. It'd originally appeared in the SP370 and 400, so any faults were hopefully sorted by the time the GN hit the road.
When it was launched, its appearance had been treated as something of a joke and its 90mph top speed treated with derision. More than anything else, the need to kick it into life, limited its appeal to the mature owner. Time could turns its electrics nasty, making starting a hundred kick affair. One good thing about the bike I was buying, the generator had been rewound and the electrics upgraded to a much more useful 12V than the standard 6V rubbish.
Thus starting was a first kick affair, though it needed a fair old boot to get the thing fired up. Carburation was very lean running but then again neither the filter nor exhaust, or indeed the carb's jetting, were standard. The pipe was nicely loud without quite shattering windows, just enough of a roar to wake up erring cagers and stop ped's walking out in front of us.
The engine didn't exactly have a power band, but from tickover up developed plenty of steam and would quite happily rattle off in third gear from a standstill, despite running taller gearing than stock. These mod's added up to the ton on the clock and quite pleasant 80mph cruising. If the engine lacked any balancers, it was at least well matched to the chassis, only really thrumming at the extreme end of the rev range.
I wouldn't admit that the engine was gutless, as it would hold 75 to 85mph against both steep hills and heavy winds. Urge was limited beyond 80mph, and trying to take a car that was meandering along at that kind of speed was fraught with danger. Acceleration could be so slow that a bout of chicken with oncoming cars, or being back-ended by an impatient cager, were always possibilities.
That meant that it wasn't an ideal motorway cruiser, though it was significantly better than, say, an MZ250. Being compact, short, and light in mass, also meant it could be knocked about by the windstream from passing artics or buses. And taking the Severn Bridge on a windy day, it felt like the bike was going to be lifted off the road and thrown straight over the side into the channel.
Weighing little more than 300lbs (320lbs stock, but some of that lost by lighter non-standard bits) allowed it to make the most of its power output. I had no problems swinging it through the bends (stronger springing and cut down stands, mind) until it squirmed right on the edge of the rubber. The narrowness of its motor meant a nice low centre of gravity, that gave an easy going, relaxed feel to the chassis. Better than an old BMW boxer!
The only weak areas are naff steering head and swinging arm bearings, showing where it was built down to a price...the build quality was so lacking that one of previous owners had been forced to strip it down, blast and powder coat all the metalwork. Even then the guards still rusted through, had to be replaced by plastic items. Luckily, I had no cosmetic problems but I've seen some real rats. Talk about ecologically sound - ie corroding back to dust!
Again, a previous owner had fixed the bearings, so all I had to do was the odd bit of engine maintenance, oil, grease, and chain adjustment. The latter could be short-lived if not kept oiled and perfectly tensioned; at best, 11000 miles for a chain and twice that for the sprockets (the larger gearbox sprocket helped longevity). I had one chain snap when the bike was overloaded and I tried to pull off in third - but it had got to the state where two links had been taken out and it needed to be soaked in Linklyfe every other week.
That happened on one of my many outings to Scotland - the back roads being ideally suited to the GN's capabilities. That time some local farmer took me into the nearest town on the back of a trailer attached to an ancient tractor. It was slow but better than walking. Typically, the spare length of chain I always take with me, these days, has never been needed.
With its modified exhaust and carburation, mild back road riding resulted in 75 to 80mpg, which squeezed over 150 miles out of the tank before I started thinking about buying some more fuel. If I wanted to play silly buggers, by riding really slowly - the mildest of revs and not more than 50mph on the clock - I could achieve better than 90mpg! Overall average was around 70mpg, making the bike exceptionally cheap to run.
As well as frugality, I also found the machine full of character. Down mostly to the beat of its thumper stroke and the genteel ease with which it would travel across the country (bars, pegs and saddle weren't stock, altered to suit my own body and riding needs). Once I'd adjusted to the lack of power, it was all too easy to decide that there was just enough motorcycle to suit any sane needs.
The paucity of power, together with superior Suzuki engineering (what, biased? - not me, it's just my experience of the breed) meant the mill was exceptionally tough. In four years I did over 50,000 miles, the clock now reading 71000 miles. And the engine hasn't been stripped down, although it has had kind owners, myself included, who think that 500 mile oil changes are akin to religion. A little bit of preventative effort with a huge pay-back in reliability and longevity.
The engine's very simplicity and fundamental correctness, add up to superior design. Weak areas, when maintenance's neglected, include the valve's rockers, kickstart mechanism and gearbox, but all of these should be self-evident on cursory examination. Chassis and bearing rot much more likely to kill off the machine. Basically, if you find one in good cosmetic shape, chances are the motor's fine.
I was so impressed that I've got two spare motors plus heaps of rotted chassis spares, enough stuff to keep her going for another 15 years!
Larry Borroughs