YOUR CLASSICS
Thailand-based Grant Holmes spent three years restoring and modifying his ’60s Honda CB. Here’s how he did it, in his own words and pictures...
The story of a three-year CB77 Honda restoration project
I’M ORIGINALLY FROM Evesham in Worcestershire, but moved to Thailand 13 years ago. I spotted this bike at a classic bike club meeting in Hang Dong in Thailand; I’ve always liked old Hondas – when I was a youngster I had a C95, a C72 and a CB160. There are quite a few old Hondas in Thailand, especially the C92 and C95 Benlys.
I’ve played around with many bikes, but this is my first full-on restoration. I wanted a practical bike that looked as original as possible, although actually it’s a bit of a hybrid – the frame is a 1962 CB72 and the engine’s from a CB77 of circa 1965. The speedo shows this is an early model – the rev counter’s needle goes clockwise, while the speedo’s goes anti-clockwise, only used for the first few years of production. The rear light is the small type; on later models Honda used a larger Stanley rear light as on early Cubs.
Everything on the bike is NOS if possible. There are any honest and efficient outlets in Bangkok that sell NOS items; I bought the wiring loom, which came with the wires for indicators, from one of these suppliers.
One of the low points of the project came after I stripped the bike completely – the frame basically fell apart after it was shot-blasted. The tubes from the shock mounts to the swingarm pivot were rotten, but I got one-inch tubing to fit after some grinding. Cracks around the rear engine mounts meant plenty more grinding and welding.
The original engine looked good on the outside, but it was completely scrap – even the cylinder head was cracked. In the end, I bought another engine from the USA and paid to get it air-freighted to Thailand. It was much better than the one that came with the bike – but it had issues. When I got it started, it was a bit noisy, so I stripped
it. I doubt whether it had really done only the 6000 miles claimed, as it was already on the first oversize pistons. The piston-to-bore clearance was excessive, so I sent the block to IMD Pistons in the UK. They provided a very good service, supplying new pistons (they manufacture their own) and boring the block to 0.50mm oversize.
These old Hondas have a problem with the conrod small end – it tends to go oval, causing a sound similar to piston slap at part throttle, as it did on my bike. Honda made four-thou oversize gudgeon pins to allow for wear, but the piston and rod have to be reamed oversize. I found some NOS conrods with bearings and asked Chris Applebee Engineering in the UK to instal them.
I also found some NOS main bearing rollers on ebay. The drive-end main bearing is a ball bearing, while all the others are rollers (there are three of them), but the bearing is labelled as a 6306 – you can easily buy these from a bearing supplier, but it won’t fit; the Honda bearing outside diameter is larger than a stock 6306.
I was prepared to carry out modifications to the bike for improvement and for reliability – and the engine was no exception. I fitted a small sprocket conversion to the cam chain tensioner, to replace the original plastic roller and bush arrangement. Also, the plastic wheel located in between the cylinders to guide the cam chain (which tends to fall apart with age) has been removed and replaced with a specially-made alloy wheel with a ball bearing race.
The oil filter is a cardboard cartridge type from a Suzuki marine engine, which provides much improved filtration and engine protection than the original rotating centrifugal filter. The housing for the filter element fits in the same location – just remove the sprocket and chain on the crank and drop it in – although I had to shim the filter to make it a tighter fit. The filter has a high-pressure differential bypass, so it will open if it becomes blocked – dirty oil is better than no oil! The original twin-gear-type CB77 oil pump has been replaced with a high-capacity pump with 7mm-wide gears (instead of the stock 4mm), which should increase the flow capacity by 45%. The oil filter, pump, cam chain tensioner and cam chain guide wheel are by US company Cappellini (see ebay). They also make a duplex primary chain conversion; the original chain is now hard to find as the pitch is unique to Honda.
The valve guides were replaced with NOS items, but were modified to accept Viton stem seals from a Kawasaki
Z900; these prevent oil from being drawn into the engine, especially via the inlet valve guide during periods of high intake vacuum. The Kawasaki Z900 and CB72/77 both have 7mm valve stems; the guides are undersize and have to be reamed to 7mm. Make sure there’s enough clearance between the top of the seal and the valve spring retainer; pressing down the valve at full lift, you need at least 1mm.
A set of four new SKF 6004 bearings were fitted on the camshaft and NOS rocker arms and pivots. The later rocker arms have an internal drilling that feeds oil directly onto the rubbing faces of the cam lobe and rocker; earlier ones used to just spray oil onto the cam. To reduce the load on the valve train, I’ve removed the dual valve springs and installed single beehive springs from R/D Valve Springs in the USA, who also supplied lightweight titanium spring retainers. All of this will help to keep down the reciprocating masses.
CLOCKWISE FROM TOP LEFT:
Early clocks have speedo and rev counter that rotate in different directions. Grant had to have the odo on this ebay purchase fixed
‘THE FRAME BASICALLY FELL APART AFTER SHOT-BLASTING’
Carburettors on the CB77 are 26mm bore, but the cylinder head inlet tract is 24mm and the 10mm-thick spacer in between the carb and cylinder head has a tapered bore. I opened up the head inlet tract to 26mm to remove any restriction from the carb to the inlet valve.
Other modifications include a set of NOS Girling shocks for a ’60s CB450 which I found on ebay – these were too long, so I cut the damper rod at the top eyelet and removed 10mm, then Mig-welded it back together.
Paul Goff (norbsa02.freeuk.com) in the UK can supply lower chrome and top painted spring covers which look exactly like the original shocks – a much better alternative to NOS Honda CB77 shocks (if you can find any). Looks just like the original – and the Honda folding-type CB72 pillion footrests I’ve welded onto the original brackets don’t look out of place, either.
The handlebars are polished stainless steel and the same style as the original low ’bar set-up, but I’ve inserted a 150mm-long solid steel bar into each end, in an attempt to lower the frequency of the vibration and prevent numb fingers. The sidestand is aftermarket item from Thailand; it fitted OK, but the spring location points were incorrect, so if you hit a pothole (there are many on the roads where I live), the stand would drop down – not recommended when approaching a left-hand bend! So the spring post on the bracket had to be cut off and relocated.
I got some bronze bushes made up locally for the swingarm bearings – they were made oversize, because the inner sleeve had to be machined due to wear and tear. A reconditioned original old stock seat was found on ebay – I paid a load for it, as usually the steel base has rotted. The indicators are the original small items – hard to find, as I believe they were an optional extra and most examples of this model didn’t have any.
Both front and rear brakes had the spindle holes in their hubs bored to accept bronze bushes, as they were oval due to wear. The rear wheel spindle was rechromed and an NOS front spindle was obtained from ebay.
Then there was the electrical system, a whole story in itself. The wiring to the alternator was reworked so it gave the full power output continuously. Originally, the alternator gave a higher output only when the lights were turned on, by connecting additional alternator windings to the charging circuit. This wiring modification can only be carried out if you have a voltage regulator, otherwise the battery will overcharge if you ride with the lights off.
Later, I replaced the alternator rotor with an early one with more powerful magnets for a higher output. But even with the more powerful magnets the output was feeble, so I started looking for an alternative rotor or alternator.
There isn’t any spare capacity in the stock alternator, therefore the headlight can’t be replaced with a higher wattage bulb, you will just run down the battery. So how to increase the electrical power? The answer was to install a Lucas RM24, three-phase 14.5-amp alternator, of the type fitted to the Triumph Bonneville – physically, it’s almost identical in size to the CB77 alternator and gives approximately 175 Watts at 13.6 volts.
The sleeve inside the original Honda magnetic rotor has to be removed – I just drilled the rivets and tapped it out. Next step is to machine the Honda alternator
sleeve and the Lucas rotor to 25.5mm and
‘I OPENED UP THE HEAD INLET TRACT FOR LESS RESTRICTION’
Loctite the Lucas rotor onto the Honda sleeve. I then drilled and pegged the rotor to the starter clutch. A coupling has to be machined to fit the Honda sleeve onto the starter motor clutch – a local guy made this, to the same dimensions as the Honda alloy coupling. The sleeve was then pressed into this steel starter coupling and silver soldered into place.
The housing for the original stator needed some slight machining (with a small cutting disc on a Dremel) and I cut down the mounting post until the head of the bolt cleared the stator. The rotor also needed new TDC and ignition timing marks, which I made using a degree wheel and dial gauge. The Bonnie alternator fits well – the three mounting holes just needed some dressing with a round file and it fitted perfectly. I used shims cut from a beer can to align the rotor in the stator before tightening it up.
This alternator should be able to give the full output at 4000rpm, so even with a 60-Watt halogen headlight there is still power left over; also, as it’s three-phase, the full power is available at low rpm
I replaced the ancient contact breakers with Tytronic electronic ignition, which uses the original bob-weight advance and retard, so I replaced the advance springs to ensure the ignition advance curve is correct. You need a stable voltage to run electronic ignition – so, as a standard CB77 doesn’t have any voltage regulation, I replaced the selenium rectifier with a Yamaha RD350 regulator/ rectifier. The position of the pick-ups are at 90° and not 180°, because the CB72/77 had crank big-end pins at 180° –one piston is at TDC when the other is at BDC, you could say they were early big-bang engines as seen in many of today’s hypersports and GP bikes!
The exhaust pipes, hand-made in polished stainless steel, came from Overlander in Melbourne, Australia, who also fabricated the downpipes. The first start-up after the restoration proved they’re not too noisy. Unfortunately, the first ride wasn’t the great experience I’d anticipated – the battery internally shorted out and I broke down. Simply fitting a Yuasa battery solved the problem.
After running the bike for a while, the right-hand cylinder started to misfire; I worked out that the ignition was to blame, so I refitted the points – but this time using two Sparkrite ignition systems, one per contact breaker. Now the bike runs perfectly.
The NOS speedo/rev counter I’d bought for $500 from the States on ebay proved to have a faulty odometer – it stopped dead at 9.9 miles with a seized drive gear. The rev counter was erratic, too, but Speedline instruments in Waneroo, Western Australia sorted it all out for me.
As regards other sources for parts, Classic Honda Restoration USA (classichondarestoration.com) supplied the hard-to-find chainguard (a copy which fits perfectly) as well as carb overhaul kits, rubber grommets, sprocket covers and other items. Dave Silver (davidsilverspares. com) in the UK has a good stock of parts, as does CMSNL (cmsnl.com) in Holland and the USA.
I’ve now done just over 200 miles on the bike – but I’ll definitely be keeping it, it’s so nice! Because of my work, I’m normally away from home for nine months of the year – but I plan to use it when I get more time at home.