Sunday, 14 January 2018

Suzuki GT500


The Suzuki engine is smooth and remote enough to let the bike cruise at deceptive speeds. The straightforward two stroke design knocks out 44hp from 493cc. The short stroke vertical twin has little by way of a power band, happy at 50 or 90mph in top gear. Acceleration is never the arm breaking Kawasaki 500 triple type of fun and games. As with so many Suzuki two strokes, the GT500 is more sophisticated and easy going than rival four strokes. Only when flicking through the five speed box and revving the engine through the redline does the GT show any allegiance to the bad old times of two stroke technology. And even then, it avoids the usual clouds of blue exhaust smoke.

The engine is well supplied with needle and roller hearings to combat the effects of poor lubrication which is the bane of two stroke technology. The separate oil supply, gear driven oil pump controlled by throttle movement, and direct oil injection combine to supply oil to parts many other two stroke designs fail to reach. The flow through the oil pump can be adjusted to reduce the loss of excess oil through the exhausts. The four bearing crankshaft lasts up to 60000 miles before needing a rebuild. Needle roller small ends have been known to break up on really thrashed engines at quite low mileages. Terminal mechanical failure occurs when the oil pump gears strip their teeth. But both of these events are rare. Bolts retaining the cylinder head can strip their threads, while engine bolts can snap off if they are not regularly checked for tightness.

The gearbox is one of those short movement devices, needing the minimum of foot pressure. As the internals age, selection becomes less precise. Once past fifty grand, the lack of feel in the box means missed changes are all too common . Remembering to change the gearbox oil every few thousand miles minimises the effects of ageing. Transmission snatch is minimal, aided by gear primary drive and cush drive in the rear sprocket.

The multi-plate clutch combines the usual Jap properties of light lever pressure with no tendency to slip when abused. It even avoids clutch drag from cold or under pressure from heavy traffic. Gears have been known to strip their teeth (especially first) but this can be blamed on lack of regular oil changes. 

The engine is housed in a duplex frame that can trace its history all the way back to 1967. Geometry changes and extra bracing marked the evolution of the original T500 to the GT500. The weakest component of the chassis is the swinging arm, lengthened to increase the wheelbase of the GT to 57 inches, but not designed to withstand the resultant increase in torque when the going gets rough. The frame is constructed from suspiciously thin tubing, that judging by the frame's weight is made from mild steel.

Suspension is quite stiff when new. With a few years wear it loses a lot of this tautness. Never well damped, both front and rear benefit from replacement. The cost conscious can obtain relief by using stronger oil in the forks and replacing the rear with a pair of cheapo Girlings. Nevertheless, even on worn suspension, the Suzuki does not develop any of the nastiness inherent in the rival Kawasaki stroker.

The combination of long wheelbase and 400lbs make the Suzuki stable in a straight line, but reluctant to flick through the curves. The ride is typically remote (for an early seventies Suzuki), the rider has to take time to find the bike's limit, hindered by this lack of feedback. On new or modified suspension all the GT needs is some extra muscle to overcome the top heavy feeling. On worn suspension, it's easy to catch the back wheel out, when the weak swinging arm adds to the hinged in the middle feeling. At such times, backing off the throttle or using the front brake can make the whole bike twitch. Throw in some bumpy roads and adverse cambers and the GT can be in real trouble, needing both lanes of the highway to survive.

Fast motorway work is no problem. The bike can cruise at up to 90mph. Passing through the wake of some articulated lorries or fighting against a steep incline requires a change down to fourth gear. Stability in cross winds is good. Combine worn tyres, aged suspension and a poor surface to induce a high speed weave. It never gets out of hand and is removed by fitting an aluminium swinging arm and a decent set of shocks. The imprecise front forks allow the bike to wander at high speeds, which keeps the rider from falling asleep. Racing with GTI owners is difficult, because the GT doesn't easily produce its last dregs of power to spin the speedo past 100mph. Sitting upright doesn't produce more than a true 95mph. A long road and crouched rider eventually attains a 105mph top speed.

The Suzuki's real failing, and one that can't be easily corrected, is in wet weather riding. Again, the awful remoteness of the tyres means there's no way a sliding tyre can be recognised until it's too late. A decent set of British tyres that gradually lose their grip over slippery patches is the best antidote. At least the geometry and weight distribution means the Suzuki comes back in line. There are far more dangerous bikes than the GT on the road. Wet weather riding drastically cuts the speed of the bike, although the lack of a vicious powerband limits the cheap thrills of wild slides. 

Once used to the Suzuki's handling limits quite rapid bend swinging is possible. It would be lost against some of the very modern iron, but can take on rival four strokes from the same era and with decent suspension can stay with its main rival, the Yamaha RD400. It's far safer that the Kawa 500 triple (but, then, what isn't?). Most British twins, with similar performance, will see off the GT down country lanes. But the Suzuki will catch up on the straights or after the British bike breaks down. 

The real improvement occurs when the GT's chassis is replaced by a Dresda frame kit. Based on an improved version of the Norton Featherbed frame, these kits cut weight by a hundred pounds, while endowing the bike with stable and agile handling that makes even the modern stuff look silly. The lower mass allows gearing for 115mph without affecting acceleration. The Dresda forks and 8LS drum front brake are top quality stuff. One of these devices is worth tracking down.

The single front disc fitted to the GT is very silly. Having no more power than the TLS fitted to the T500, it doesn't work at all well in the wet - nothing happens for the first few moments then the wheel locks up. Pads last for around 7500 miles, and the caliper needs to be stripped down when pads are changed to stop it from making strange noises and/or seizing. It requires minimal finger pressure to operate , but in the dry it's difficult to control because it lacks any useful feedback. SLS rear drum brake is sensitive and doesn't lock the wheel. The rear wheel copies old British technology by being quickly detachable - remove the wheel spindle and spacers, letting the wheel come away while leaving the chain and sprocket in position. It's a pity no-one else bothers with such niceties these days. 

A rear Roadrunner goes for at least ten thousand miles while the front can make it to fifteen grand. Those who like to live dangerously will find that a worn front tyre can step out in a suitably suicidal manner, while a slick like rear will induce some nice weaves at speeds above 60mph. Worn tyres with no feedback are not a good combination. The long swinging arm and small engine sprocket extract their price on chain wear, which can be as little as 5000 miles, although modest riding and regular maintenance can double its life. Worn chains are very prone to snapping - they don't usually break into the crankcases, just make a mess of the chain cover. Swinging arm bearings are prone to rapid wear, often in need of replacement by as little as ten thousand miles. Bikes involved in crashes bend the down tubes of the frame with absurd ease, if the engine looks out of line with the horizontal plane, then the bike's been in an accident.

Stock silencers can last for up to five years. They tend to rust on the outside first because of the oil coating they receive from the exhaust fumes. A large array of expansion chambers are available that increase noise and decrease performance. It's also possible to tune the engine, enlarging the ports, increasing compression and dumping the air filters. This tends to destroy the nice nature of the engine and reduce reliability. It's far better to go for a stock engine.

The style of the GT is wrecked by a slab sided tank and poorly integrated side panels. Available in a bland shade of blue, the Suzuki signed its own death warrant when it was introduced in 1975. There are many bits and pieces that can be bolted onto the Suzuki to improve its appearance, especially a nice line in alloy petrol tanks.

The earlier version of the GT, the T500, looks far better because it has a classically rounded tank that highlights the robust lines of the engine. The T500 was also faster, with 50hp and 110mph. Combining wilder acceleration with a poorly braced frame and soft suspension makes for interesting road manners. The bike was helped by a little more feedback but it was easy to lose the back end on bumpy curves. Suspension and frame were improved in '72 , but even then they are inferior to the GT. The more powerful motor had a shorter life, needing a new crank and rebore by 50000 miles. The engine had some of the blood and guts feel of the Kawasaki 500, but it was never as dangerously wild as the triple. Acceleration to 60mph of under five seconds will still surprise many modern bikes.

The T500 averaged 45mpg, while the later 500 managed 50mpg. For sure, thrashing the GT at maximum revs would increase that to 35mpg, but more moderate 90mph cruising returned better than 40mpg. Pottering around on the minimum of revs but staying up with out of town speed limits can return as much as 60mpg. With just over three and a half gallons the GT had an effective range of 150miles before needing reserve.

Riding position suffered from the usual forward mounted footrests that didn't match even the raised handlebars. The GT could be cruised for about an hour before the poor stance inflicted on the rider meant a sore backside and strained arms. The seat was firm, slippery and retained water. Not a good combination. Flat handlebars and rearsets help redistribute extra weight over the front wheel, aiding stability.

Starting is only difficult because the kickstart is on the left hand side. The force needed is minimal and the motor comes to life on first or second kick. Those ignorant enough to pump the throttle before the motor has fired will oil up the spark plugs, because this operation increases the amount of oil flowing through the engine. Stalled engines can be started by pulling in the clutch and kickstarting, without the need to waste precious moments finding neutral.

Lights are entirely inadequate, quartz halogen units are recommended as the engine doesn't produce sufficient vibes to affect them. Unlike some of their four strokes, the alternator and rectifier are both made well enough to avoid burning out. Handlebars switches are water resistant, but the light switch is a trifle awkward to operate when wearing thick gloves.

The GT 500 is very practical motorcycle that can provide plenty of cheap fun. Even with ten years of wear and abuse there are still many bikes on the road with plenty of engine life. This is quite remarkable for a two stroke design. The likes of Yamaha RD400s and Kawasaki KH500s are on the scrapheap in much less than half the 60000 mile engine life of the GT. There are plenty of cheap spares and tuning goodies. The engine is simple to strip down and easy to maintain. Ignition timing can be done without a strobe. Even if it's not spot on, the engine avoids burning holes in the pistons or seizing.

The ride quality and handling abilities are a little dubious. Most of this can be sorted by fitting decent suspension and a stronger swinging arm. Many used bikes will already be modified. Try to avoid those that have heavily modified engines. The GT tends to attract rather more sedate riders than the T500, which increases the chances of picking up a good bargain. Nice examples of the T500 are now very rare. The GT500 probably won't make it as a modern classic because it doesn't have the looks. So the bike's far from perfect,but prices start at £200.

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