Wednesday, 3 February 2016

Honda CB250G5



Okay, okay, stop laughing at the back... yes, I am the proud owner of a 1975 Honda CB250G5! Acquisition of this miracle of seventies engineering entirely accidental. Three years ago an elderly neighbour asked me to demolish her shed and there the little twin had hidden for a few months after her husband's death. It was such an inoffensive machine that I had barely noted its existence over the years but could recall the exhaust blare of a Sunday morning, presumably the guy giving it a weekly start whilst he was on his last legs.

The G5 had a reputation back in the seventies for self-destructing camshaft bearings, which could be terminal as they were part of the cylinder head! As a later model that had survived for 25 years I presumed that either Honda had belately fixed the problem or the bike had such an easy life that it never became a hassle on this particular machine.

This is what is known as living in hope... even after fully charging the battery, the vertical twin resolutely refused to start. After flattening the battery, I knackered myself on the kickstart. It then dawned on me that maybe the fuel had gone off and I'd best drain the system and refill with new gas.

That was how I found out that the rubber hose from the petrol tank disintegrates if you give it an encouraging tug. A fiddle with the tap – which looked like it came off an old Brit bike, perhaps a replacement for Mr Honda's not so fine original – finally emptied the tank. Well, not quite, the fuel had stopped running out but there was still some in the tank. And, yes, it was on the reserve position. Okay, the wire mesh filter was all clogged up with gunge and the rest of the day was spent cleaning out the fuel tank and carbs.

After all that effort it still refused to start. Depending on who you believe, the G5 isn't worth collecting if it's a non-runner or might be worth a hundred notes on a good day at an auction. There's an high art to removing spark plugs from aged Jap alloy, with a tendency for threads to corrode in. Even more so with stuff like the engine screws, a whole day spent removing the more recalcitrant ones. But out the plugs came without ruining my day and in went brand new ones, with a smidgen of grease to ease their way in (down at the back, there!).

By then I had recharged the battery, after applying full choke, hopefully caressed the starter button. Clunk, clunk, clunk, whirl, whirl, whirl... and then some promising detonations in what appeared – if the level of rust and corrosion were any guide – to be the original exhaust. A moment's rest for the mill and then hit the starter again with no pressure on the throttle; the little blighter caught...

And promptly whirled around to about ten zillions revs. One throttle cable pumped full of grease later, the bike was merrily ticking over at 1500 revs and sounding like it had just stepped out of the crate. That is, before anyone had a chance to adjust the valves, carbs or timing... a little hunting on the web got me the info to do those chores and...

Well, the little bugger wouldn't start again! Once the oil was cleaned off the plugs she (has to be a SHE doesn't it?) was all go again. Until I tried to engage gear – the bike leap a good yard forwards and then stalled dead. Clutch drag didn't come into! A repeat procedure with the front brake hammered on whilst my groin burned with the indignity of being battered against the tank, finally allowed the old steamroller to meander off down the street.

Aha, big grin time. Well, until we approached the junction and I found that the front disc – a marvel of technology back in the seventies but sheer rubbish, these days – did not work in any manner recognisable as retardation. Okay, you could say that the rider was a bit retarded for not checking it before applying any serious speed, but it had seemed to work at a standstill and the sheer excitement of getting the little bugger running combined with advanced senility...

The rear drum slid us to a halt, a foot over the white line, causing one geriatric driver to nearly hit an oncoming car as he swerved to avoid what he must've assumed was a suicidal motorcyclist. Adrenaline overdrive added to ruined marital tackle, my sense of foreboding intensified by the way both silencers fell off as I made it back to my driveway in one piece. Alarmed residents of the formerly quiet suburb were seen clutching their curtains at the apparent terrorist incident going down in their street. I quickly killed the engine dead before becoming the centrepiece of advanced army and police retribution.

Ever the optimist, I decided that the bike needed a few bits and bobs to sort. There's an art to cadging spares off mates that has more than a little to do with blackmail and coercion... and if that doesn't work the odd bit of desperate pleading and quickly forgotten promises. It took a whole three weeks of such activity until the bike was ready for the road again. Additions included such niceties as a GS450 front brake, pattern Bonnie silencers, CB500/4 seat, auto rectifier and regulator, and a set of genuine – probably worth more than the whole bike – Vincent flat bars fitted with equally genuine Prince-of-Darkness switches! Yes, I have some very sick-minded mates!

Of course, the Honda reacted to these foreign objects by refusing to start. Another cleaning of oil off the plugs session and a push on the rather large second horn button that now connected the battery to the starter's solenoid, had the flames of combustion doing their trick. A very healthy rumble that would surely convince any but the most brutally pedantic fanatic that he was hearing a British twin in all its hallowed glory.

The silencers so well matched to the carburation that there was a 4000rpm flat spot from 3000 revs up. Combine that with the sixty-six-false-neutral gearbox to end up with forward motion that threatened to cause highway carnage from cars back-ending us! At least there was a discernible and seemingly potent power outpouring once it finally hit home. Hmmm, some more work needed – at least the front brake now worked.

Do not under any circumstances remove aged carbs from a seventies Honda twin. Not unless you want to waste four weeks trying to find some rubber manifolds to replace the cracked to oblivion from heat-brittleness originals! A patched set of ancient originals the best I could do. The Honda actually ran as well - if not better! - than its manufacturer intended. Amazing what you can do when armed with sheer stubbornness!

Some further refinement with gasket goo and Aradite stopped the carbs and manifolds falling off – Honda obviously had a reason for using rubber as an interface between carbs and cylinder head. Now get this, despite the desperate bodging the little twin regularly turned in 70-80mpg, which being a bit of a miser immediately endeared the bike to me!

All was well with the world for a week, or so, when the front mudguard decided to disintegrate with me at the controls doing about 60mph! Face is all in the Orient, the guards rust from the underside, look okay until little bubbles of rust show up as a warning that they are about to fall apart. I thought the whole front end was disintegrating and it was just as well that I was fitted out with a colostomy bag... the GS450's guard was fitted but that didn't look like it was in much better shape and as soon as the cadging located them a set of plastic guards were fitted.

I had little faith in the chainguard and after a close inspection even the bloody swinging-arm looked likely to go the same way. The back always impressed with its looseness but I put that down to wimpy swinging-arm bushes and pogo-stick shocks. You can't expect old hacks to handle sublimely, lucky if it goes where it's pointed and doesn't throw you in the nearest ditch when cornering. All told, the 360lb Honda was still controllable and I normally wouldn't have been too concerned but the idea of the swinging-arm breaking up had got a hold of what was left of my mind.

Then I read about the likelihood of old Jap wheel alloy breaking up and had a look at the back drum – hairline cracks revealed after a decade's crud was wire-brushed off! Put a match in the petrol tank my mates chorused but I mumbled something about there being a lot of life left in the engine and it doing 80mpg and 80mph on a good day (okay, it probably wouldn't do 80mpg when it was doing 80mph).

After a total disassembly of the rear end, the swinging-arm's rust was revealed to be of a surface rather than deeply ingrained nature whilst the bushes were – unbelievably – plastic! Shocks meant for a CB500/4, phosphor-bronze bushes made up by a mate of a mate, and a GS450E back wheel were lovingly reassembled with the biggest available hammer that I could lift, helped along by death-threats and prayers.

To be perfectly honest, back end stability and braking felt exactly the same as it did before – most likely down to the reuse of the mismatched, worn and total crap rubber whose only redeeming quality was that it was impossible to wear out the remaining 1.5mm of tread. A weird defiance of the laws of physics but nevertheless true, officer.

These arcane elements of cheap biking important when you're on strict budget. It's not that I'm exactly impoverished just that wifey has the cheque book and doesn't like motorcycling! Any excuse, I'd be back on the push-bike!

These ill-omens may give an impression of a bike about to disintegrate under me and there was certainly a bit of edginess to my first half year with the Honda but then we managed to settle into each other and get some fair mileage in.

Chronic problems include a clogged reserve feed that has tried to strand me many times – if you ever came across a pensioner furiously shaking a G5 that was probably me trying to dislodge the gunge from the wire mesh! Oiled plugs if the bike is used moderately – it has a stroker-like need to clean out its combustion chamber though confusingly I have yet to find any oil being burnt off either out of the exhaust or engine breather. And old Honda gearboxes are worth a whole article to themselves – low cunning and fresh oil (every 500 miles!) gets the better of them, most of the time, but it can be intensely embarrassing to find the engine revving through the redline thanks to a false neutral! The vagaries of Lucas switches well known to devotees of Brit bikes but nothing that WD40, Vaseline and the odd desperate prayer can't sort.

The speedo now sports an incredible – for a G5 – 78000 miles and the actual engine, unlike the chassis, shows no sign of dying. Performance is on the sedate side but it is certainly faster moving than modern 125's and even the bigger scooters. The level of refinement merely that of a well sorted Brit twin and every ride has an element of unpredictability but it keeps on rolling and costs very little to insure and run.

For a free bike, complain I should not, but if you come across one look out for the corrosion and be prepared to update suspension, braking, silencers and anything else made out of metal outside of the actual engine and frame. By the time I am finished with the little bugger I expect the only original component to be the frame – but that grand finale is some distance off yet.

W.H.K.

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