Advice: Technical Q & A

SOAPBOX
Elsewhere in this issue you’ll see coverage of changes to the compulsory third party charges for motorcycles in NSW. It’s an odd mix of changes that seems to have elements of social engineering in it.

There’s an 84 per cent increase for 250s but a 30 per cent decrease for bikes in the upper end of the learner-approved scheme. The 1000cc bikes are pretty much unchanged, but 1150  to 1340cc bikes cop it hard.

This stuff is usually worked out on the basis of claims – if the claims are up in a particular category, it’s reflected in the premiums. What the July 1 changes do, though, is attack the viability of the cheaper end of the bike market, discouraging entry-level bikes and riders (read poor people). It would be nice if the people and bodies behind these changes explained them rather than just declaring them.

It’s also worth looking at John Murdoch’s letter in this month’s column on the legality of fitting LED display lights under his cruiser. Like insurance premiums, the laws differ from state to state. Why can’t we have some kind of national consistency in licensing, insurance, road rules and mechanical modifications? How can something be safe in one state but unsafe in another?
If I run for parliament, will you vote for me?

MISSING YOU
I am the owner of a 1991 BMW R100R I’ve had for about seven years. From the beginning, the engine has had an intermittent miss in the left-hand cylinder just off idle.

Over the years many things have been tried: compression checked, tappets adjusted, changed spark plug caps, changed coil, new leads, checked cam timing, cleaned carbs, replaced main jet O-rings and diaphragms. I’ve also checked for air leaks around the intake manifolds and throttle shafts. I even purchased vacuum gauges to do the carbs. The bike has done about 68,000km and I have a sense that it has a noisy top end. It uses a small amount of oil (100ml per 2000km). Nobody who has worked on the bike has been able to solve the problem so I’ve just put up with it. Otherwise, it goes great. I seek your wisdom.
- Dan Roberts
Dan.Roberts@live.com.au

Start with a coil test, Dan. I see that you’ve replaced the high tension leads but BMWs are particularly sensitive to this and the HT leads should be genuine BMW. It’s also important that five kilo-ohm resistor caps are fitted. I have a feeling that this might solve the problem but get back in touch if it doesn’t.

Being air-cooled and sitting underneath you, you get to hear a lot of engine noise. Yes, there’s a difference between bad noises and good noises, but if it sounds the same all the time, the noise is probably normal. The very small amount of oil the bike uses suggests the engine is in good condition. Get back to me when you’re using a litre per 1000km…

Unless the clutch cable has been adjusted wrongly and the clutch is slipping, the engine will just be loafing along at 100km/h in top gear. Get someone with some experience to see that there’s a little bit of free movement in the clutch lever before it starts to pull on the cable.

All good? What’s probably happening, Chloe, is that it sounds to you like the engine is revving its head off but it’s actually a long way from being stressed. Our test bike got to 130km/h in third gear before the ignition cut-out told us to change up to fourth.

When you’ve run the bike in properly (varying the speed in a range of operating conditions and making full use of the gearbox for around 1000km), you should rev the engine out in the lower gears to hear what it sounds like when it’s close to the maximum allowable revs. You won’t blow it up because the engine will stop revving by itself when it decides any more would be damaging. I think you’ll be surprised by the noise it makes but it’s all mechanically safe.

It’s a pity for learners that the Venox doesn’t have a tachometer, a gauge that tells you how many revs the engine is doing. The low revs you’d see in top gear at 100km/h would make you feel a lot more comfortable. 

KEEP YOUR OLD COPIES
I’ve got an old Yamaha SR500 and remember reading in a past issue about some list you were compiling that mentioned a workshop in Brisbane that was willing to work on older bikes. It might have been in #226 – I have it somewhere around the house but I can’t find it. Can you remember the name of the business?
- Ben Yee
benny.yee@gmail.com

You’re in luck with the SR500, Ben. Partly due to the excellent work done by the very active SR500 Club (PO Box 500, The Patch, 3792) and a cult following being encouraged by businesses like Deus Ex Machina, there’s plenty of product knowledge and parts to keep SR500s running. Plenty of SR400s are also being imported too and you can put a 400 engine in a 500 frame with very little trouble. In fact, Yamaha Australia is currently deciding on whether it will start importing new SR400s for sale through Yamaha dealerships.

Some specialist SR workshops have sprung up and two of note include Andy Brebner’s Single Obsession Motorcycles (0401 715 088) and Mischief Makers in Melbourne (0407 925 561). Yes, they’re both in Victoria but the movement is spreading…

What an excellent find, James. I’m a bit surprised it runs well after 25 years of storage, as what often happens with old two-strokes that aren’t used is the crankshaft seals dry out and then leak when the engine is started again. The sign of this is massive amounts of smoke coming out the exhaust, sometimes only on one side depending on which seal gives way first. If none of this is happening for you, you’re blessed.

With its light rust pitting on the chrome (very common with Japanese bikes from that era) and light rust on the tank, your bike fits into the survivor class – original but unrestored. In the car world, survivors are generally worth more than restored examples and the same thing is starting to happen with bikes. The really collectable Suzuki 250s are the ’65 to ’69 T20s variously called Super Six, X6 and Hustler. Your ’71 example follows the more modern styling introduced with the 305 and 500cc twins. They’re less collectable but still lovely, with their front drum brakes, six-speed gearbox and fabulous top end.

Prices vary widely at the moment but, as we’ve discussed before, early, small-capacity Japanese bikes are the next big thing. If it’s money you’re after, just keep it nice and wait. If you want to sell it now, a starting price would be $2000 and a really keen buyer might go to $3000. Not too shabby when you consider they were $699 new!

You’ve had what we call in the trade a ‘sobering experience’, John. What you’ve said makes sense and there’s no easy solution. A little bit of heat on the screw heads may help break the bond but there’s a limit to how much you can apply because you’re working around plastic components. R 1200 RT owners, be warned…

The standard front sprocket size is 18-teeth, Kevin. Honda offers smaller sprockets (15, 16 and 17-teeth) but nothing larger than 18. It would be possible for you to have a non-genuine sprocket made with one extra tooth but the fact that Honda doesn’t offer one suggests there may not be room in the casing at the end of the countershaft. The obvious plan B – a smaller sprocket on the rear wheel – won’t work either, as the standard size is 39 teeth and Honda’s only options are larger (42, 43 and 44), not smaller. It’s odd that the bike should be in the showroom fitted standard with the highest gearing available. If your bike’s second-hand, it’s worth counting the teeth to see if the previous owner had the gearing lowered.

You’re in luck, Michael, in that the stock mufflers are circular and straight, meaning they shouldn’t be too hard to copy. I’ll break my rule about not recommending individual businesses (for about the millionth time) in directing you to Megacycle in Melbourne. Ken has been in the business for decades and can create from scratch. Cost could be up to $750 a pair but could be cheaper depending on your requirements. Megacycle’s number is (03) 9769 1200.

There’s some small writing on every tyre, Nick, that tells you the maximum load rating and at what psi this is achieved. An example would be 315kg at 42psi. It’s not a recommended tyre pressure – just information on the pressure required to facilitate the maximum load indicated. Motorcycle manufacturers obviously have to specify tyres with a load rating in excess of the weight of the bike and this is partly because the load changes, particularly on front tyres, under heavy braking.

There has always been tension between tyre manufacturers and motorcycle manufacturers over recommended pressures. During testing, the manufacturers will determine a pressure which is enough to keep the tyre safe in its performance and assist in the ride quality of the bike. Ride is improved with lower pressures. Tyre manufacturers inevitably prefer slightly higher pressures as the tyres run cooler, last longer and don’t distort as much. They think if bike manufacturers want a decent ride quality, it should come from the suspension set-up, not the tyres. Where are you getting wear on your ST, Nick? If the pressures are too low, you’ll get irregular wear either side of the contact patch. (Conversely, if you run pressures too high, you’ll get wear on the contact patch itself). As I say, as a general rule, bike manufacturers will lean towards lower pressures and you might find an extra two or three psi will stiffen up the ride a little but give you better tyre life.

RED MENACE
In years to come I would like a restoration project, but I’m not in a position to do this just yet. I had a rush of blood recently and bought an ’84 model Kawasaki GPz900R. It was cheap and it was right in front of me. It has scratches, a broken fairing and a broken indicator. The engine’s done 95,000km. The cam and valve noises remind me this is not a new motor, but the previous owner has been commuting on it each day with reliability. It seems to have lost little compression and it still goes like the clappers. My plan is to mothball it for up to five years – I’ll knock up a crate that will be air and water-tight. What advice could you offer about preparing the bike for preservation? To ask the question differently, if you were to open the crate in five years’ time, what sort of things would you have wished had been done?
Russell Edwards
Russell.edwards@parchem.com.au

Aha, the old rush of blood… Wash the bike thoroughly and take it for its last ride, Russell, getting it up to normal operating temperature. Dump the oil and change the filter. Refill with fresh oil. If you leave the old oil in it, the water and acids in the used oil will eat a nice line along any engine or gearbox components sitting in it. Run the engine again for a couple of minutes to circulate the new oil.

Flush and replace the brake fluid as contaminants in the existing fluid will turn it into jelly over time. I’d also drain and refill the cooling system. Use the ready-made-up Castrol coolant as the proportion of corrosion-inhibitors in it is correct – something you can’t guarantee with the green cordial in the cheaper brands. Remove the fuel tank and drain the fuel from the carburettor float bowls. Empty the tank, let it dry out and then put about half a litre of two-stroke oil in it. Put the fuel cap back on and shake the tank around so that the oil coats its inner surfaces to discourage rust.

Now remove the spark plugs and put a few squirts of the left-over two-stroke oil in each cylinder. Turn the engine over a couple of times to coat the upper cylinders. Replace the plugs to finger tightness. Clean and lubricate the drive chain and remove the battery. Ideally, you’d put the battery on a trickle charger once a month or so to remind it of its job to store electricity. Give the bike a light spray with WD40 and spray some up the mufflers. Put plastic bags over the ends of the mufflers to prevent the entry of moisture. Leave the bike on its centerstand to keep weight off the tyres. Geeze, looking at all this, it might be easier just to restore it now. One thing you can do while it’s in storage is keep your eyes open for second-hand body parts – fairing, side covers etc. When you do get to the restoration stage, these will be the bits hardest to find. Best of luck.

Daphne must have fallen in the water, John – when we opened the picture all we could see was your bike! The LED display lights will have minimal influence on the electrical system so don’t worry about that. Regarding legality, our stupid Federation means we currently have different laws in different states. The Queensland Department of Transport at least has the common sense to produce a booklet on what’s legal and what’s not in the way of modifications. It’s not comprehensive but it’s a useful guide. There’s an on-line version of it at

Local Queensland gossip is that the lights can’t be blue (or yellow), and can’t flash. The lights also need a remote switch to turn them on and off. The Queensland coppers on the street won’t, of course, be aware of any of this, so it won’t stop you being pulled over. Carry a copy of the modifications booklet with you when you ride.