Sunday, 7 January 2018

Moto Guzzi Le Mans 850 Mk. 3

The gearchange has all the precision of a sawn-off shotgun, the shaft drive tries to whip the back wheel off line when the power is turned off in bumpy corners and all the controls are heavy enough to send the muscle building industries right out of business. Oh, and acceleration up to 70mph was about on par with a good Jap four hundred twin. But these are minor quibbles when compared with what the Guzzi can offer out on fast country roads when all the elements of the bike's design begin to make some sense.

Guzzi claim some 78hp for the Mk3, but this can be taken with a pinch of salt as the bike goes no faster than the earlier Mk1 which claimed a mere 70hp. The layout of the engine should be well enough known for me to avoid boring you to death with paragraphs of mindless technical prose. Suffice to say, it's a V-twin with pushrod operated valves and a five speed gearbox. It's been around for well over ten years, so most of the problems should have been well sorted. The Mk3 has specially coated bores which mean that it can't be rebored, although the process is supposed to let the pistons and bore last rather longer than conventional cylinders . The older bikes were often in need of a rebore by 50000 miles, the largest distance covered by a Mk3 that I could find was 42000 miles and there didn't seem to be any significant signs of bore wear, so the Mk3 might well manage to run for quite large mileages.

Although the bike can potter along at 35mph in top gear, any attempt to accelerate will send tremors of rebellion throughout the length of the machine. It really needs to drop a couple of gears at low speeds to get the power turned on without the engine trying to separate itself from the frame. Torque reaction, I believe it's called. With the cylinders spaced at 90°, primary and secondary vibes effectively cancel themselves out, leaving the con-rods and pistons, which are slightly out of line with the opposing set, to try to twist the crankshaft. The effects of this depend on engine revs, but only really manifest themselves at certain revs, as the frame and engine can be designed to absorb the vibes for most of the time. Whatever nastiness the engine produces it's way ahead of vertical twins, less intrusive than some secondary vibes from Jap fours, and a little bit more pleasant than certain Kraut flat twins. The Guzzi is most relaxed between 80 and 115mph, a speed when, anyway, most of the interesting power is produced.

Riding in town does not really suit the chassis. The front forks get some help from air suspension, making them a little more compliant than on the older bikes, but the Guzzi still relies on stiff, short movement suspension to obtain that secure, sure footed feel at high speeds. Thus town riding has to be sacrificed for high speed fun and games. Gunning the engine in first or second is about the only way to get it to shift at low speeds, but the engine never feels very happy given such lack of sympathetic treatment. A heavy throttle and clutch don't help things in town, either. Just using the brake pedal to operate the linked brakes is the only easy option available. And the system seems well enough designed to cope with all kinds of road surfaces.

At low speeds the chassis takes a bit of effort to fling 460lbs around, but with the exception of backing off the power, it's really quite stable and there's always plenty of feedback to make sure the tyres never let loose without warning. The bike is long and low, the faster it goes the more stable it feels. Above 70mph, the suspension begins to work properly, actually absorbing some of the bumps in the road. The Japs can design suspension that is good at both low and high speeds, but the Italians are still building forks and shocks that don't wear too rapidly, so that with equally aged bikes the Italian stuff is going to come into its own and the Jap stuff become increasingly imprecise.

Precise steering is something that the Guzzi always seems to retain, regardless of how old or how thrashed the bike has become. The bike is rock steady at the ton, quite easy to throw through fast bends and has that delicious feeling of security that only the better Wop and British bikes seem able to achieve.

The Guzzi uses a tubular frame that has excellent support for the steering head and swinging arm pivot. The bottom frame rails are detachable to allow the engine to be removed; a system of which I can hardly approve - if the detachable rails aren't really needed why bother fitting them, and if they are wanted then they need to be more securely attached than via a couple of bolts. The large chunk of alloy engine housing must contribute quite a lot to the strength of the frame. 

The chassis is really only upset by worn tyres ,which when down to 2mm, let the bike develop a slight weave above the ton, which can turn quite nasty flat out at 130mph. On illegal tyres the Le Mans can turn in some quite amusing speed wobbles. Fortunately, merely backing off the throttle lets the bike regain its composure.

Wet weather riding could also turn a little frightening if the engine speed was mismatched with road speed when changing down. This would either stall the back wheel or have it spinning out of control . Under such ill treatment the back end a will try to lurch around 3 and catch up with the front wheel . This problem is rather more pronounced than on, say, a BMW, and can get rather violent if the engine is just coming on cam at that particular moment. This is all rather a pity because otherwise the Guzzi is eminently stable and safe in wet weather. If the bike wasn't quite so unhappy at low revs in high gears it could have been run along in fourth or fifth for most of the time , but this easy option was denied and there was no way I could relax on the Guzzi in wet weather.

At such moments it might have been helpful to be able to operate the rear brake on its own, so that such machinations could be kept under control. This marginal loss of control was more than made up for by a braking system that was sensitive enough to avoid locking up the wheel in wet weather, yet didn't suffer any of the wet weather delay of many rival systems . Once I managed to restrain my right hand, I relied solely on the brakes, as they provided all the stopping power I ever needed and the extra freedom afforded my right hand was most welcome.

The handlebar fairing was better than nothing in wet weather, but was hardly up to the protection afforded by the BMW RS fairing. It was possible to get a little more protection by ducking down behind the screen, but it wasn't really enough to justify the assault on the old bike's appearance. The Mk1 had a raw and brutal look that was lacking in the squared off appearance of the Mk3.

Even on a bike that was only three years old, with only just over ten grand on the clock, the paintwork on the frame was beginning to rust away and some of the chrome was starting to flake off. The finish was better than earlier efforts. When paint would peel off the tank and the exhausts would turn bright red after only a year. It's still not exactly inspiring stuff.

The gearchange and clutch action.are marginally improved over earlier efforts but they don't represent the same kind of progress found in gear swapping as evidenced by BMW twins over the past decade. When new, the action is just about acceptable but with ten grand on the clockthe box needs very precise coordination to attain a clear change, any fumbling becoming immediately apparent through the very direct shaft drive. This isn't anything to really worry over, as a bit of riding soon masters the technique and the problem fades into the background. Problems with switchgear don't disappear so easily. It's not that they can't be operated easily, more that on occasions operating the switches fails to produce any results. Indicators that blip at varying rates are merely amusing, but headlamps that fail to light up when expected are a little more disturbing. The switches themselves are quite well placed and quite positive - it's just a pity they only operate sporadically.

Problems with the Guzzi engine usually arise due to neglect of maintenance. Earlier bikes used to like to wreck their shaft drive oil seals at amusingly low mileages - and even a couple of Mk3s managed to keep up this quaint tradition at around 20000 miles. Valvegear can be a problem at thirty grand with worn out tappets and burnt exhaust valves the main areas of concern. The crankshaft is pretty tough, but the dry diaphragm clutch can also give up the game at thirty grand if the bike's been abused. The gearbox doesn't fail, it just gets less and less precise as time goes by. The most that could be expected of the older bikes was 75000 miles, but they were often in the casualty ward by half that distance. It's a bit too early to give any definitive data for the Mk3 but it certainly seems no worse than earlier bikes The whole of the electrical system from the generator up has to be viewed cautiously.

Fuel economy wasn't up to the standards of the earlier bikes. Under mild use they could return up to 70mpg, but the Mk3 wasn't able to better 50mng and could often do worse than 40mpg. Expect around 45mpg average.

Rear tyre wear was not inspiring either. Around five grand seems to be the average. Blame the high mass and direct shaft drive. The front tyre could go for a little under ten grand. Brake pad wear was also frightening with five grand the most that can be expected . Some money can be saved on servicing, as everything is nicely straightforward. The only tedious business is keeping the carbs in balance as they are often out in just 500 miles - this increases vibes, fuel economy and the engine's dislike of low revs.

OK then, the Guzzi can't suffer the same kind of neglect as some of the Jap stuff, but it's equipped with a nice line in the chassis department, feels wonderfully relaxed as a 90mph cruiser and even in its Mk3 form looks quite flash. And, with a bit of loving care and attention, the engine will last for reasonably long mileages. Personally, I wouldn't spend the fifteen hundred quid necessary to get hold of a decent example, but then I'm not convinced that such large sums are needed to enjoy my motorcycling. You could do a lot worse.

No comments:

Post a Comment

Note: only a member of this blog may post a comment.