Mark Haycock with two pages of tips! Win a Venhill £50 voucher!
❙ Q&A
Our very own wizened sages, Messrs Mark Haycock and Steve Cooper, are here to answer all of your woes, be they mechanical or spiritual. Every month we will be giving advice, as well as some general tips. Don’t forget to send in your own tips too. LEVER BENDING
Q:
Just a quick comment about the bent clutch lever on Mark Haycock’s TX750. Mark says that he wouldn’t advise straightening it, but I have successfully straightened them in the past. The issue with alloy levers is that once bent they ‘work harden’ and become brittle so any attempt to straighten them runs the risk of them snapping. The solution to this is to anneal the metal by heating and quenching it before bending it straight. (Rub soft soap on the alloy and heat it with a blowtorch till the soap goes black, then quench).
Get Mark to give it a go; he’s already fitted a replacement lever so has nothing to lose and a bit of original quality to gain. The same technique can be applied to copper washers to allow them to be reused in an emergency, but I wouldn’t advise trying it on brake levers as the risk of one snapping in use is best avoided for safety reasons!
Mike Brown
A:
This was Mike's letter from last month, so I decided to see if it works! I must say I was a little dubious as I wondered if this aluminium alloy is really the normal rather brittle composition used by the Japanese manufacturers for engine cases as it works well for die-casting. I was thinking that this alloy would be probably something along the lines of Zamac (usually called Mazac in this country, although they are not quite the same thing) which is an alloy of zinc, aluminium, magnesium, copper and other things. Or is it, because on reflection that surely would not be strong enough for a handlebar lever?
Let’s start by comparing the two levers (Photo 1) and you can see that the old lever has been bent at the outer end, so to preserve the original shape this is where the rebending needs to be concentrated. What I propose to do is to hammer the lever near the ball end on this heavy block (Photo 2) which will act like an anvil – after the annealing, that is! Now, about the temperature measurement. I didn’t have any soft soap so I wondered if this scrap of ordinary bar soap would do (Photo 3). This type of infra-red thermometer (Photo 4) can be useful for this sort of temperature measurement, but unfortunately it does not work properly on shiny metal, so it will be no good here.
I held the lever at the pivot end with a pair of grips and used an ordinary butane blow-lamp as I did not need to get the lever very hot. I can tell you that the solid soap was useless so I just had to go on the appearance of little bits of smoke and welding-type smells, as well as a slight discolouration of the shiny parts of the lever, to gauge when the lever was well and truly hot. After quenching the lever in water (Photo 5) I followed my hammering proposal and – how about this! (Photo 6). Not a bad result! So Mike’s idea does work (ostensibly, because I should have tried it on another lever without the annealing to get a definitive result), but I do agree that you would need to be braver than me to use it on a brake lever.
By the way, annealing does work and is one I use regularly to renovate copper parts such as sealing washers, but my understanding is that it is only actually necessary to heat the bits up to a bright red heat. The quenching is not actually part of the process as it is with steel, but it does help to remove the scale which will have formed on the surface. The lever alloy might well have similar properties, but of course the quenching does avoid unthinkingly picking up a very hot bit of metal!
Q:
I recently had the wheels of my Kawasaki ZRX1100 powder-coated and new Metzeler Roadtecs fitted. Unfortunately the stick on balance weights that were used came off within three days. I then had the wheels rebalanced and new weights put back on, and my bike was parked in the garage due to lockdown. On checking my bike a week later I found the balance weights lying on the floor of the garage. Help this old pensioner to get the balance weights to adhere to the wheels!
Dave Hewitt
A:
I am assuming, by the way, that the adhesive is detaching from the wheel rather than the weight? If the latter, then your tyre workshop must be using poor-quality weights, but if the former the powder-coated surface must be extremely smooth and impervious, so I am afraid the only way that I can think of to make the weights stick is to make it less so, but of course only in small specific areas. That means getting the balancing done yet again, then if you manage to get the wheels home without the weights dropping off, marking the position of the weights – probably masking tape would be best – then levering off the weights and giving that small area a rub with a bit of wet and dry and cleaning it carefully with solvent.
Then get all traces of adhesive off the weights and similarly sand and clean the sticking surface. You could then use a good epoxy adhesive, but I would not recommend that because it will be very difficult to get the weights off when they are next rebalanced. Better would be good double-sided sticky strips such as Unibond No More Nails, which is okay for exterior use and (it says here) will hold 120kg per roll. That works out to 4.2 grams per square millimetre, which does not sound much but I have just measured a 20-gram weight at 15mm x 37mm and according to my calculations the strip can hold 116 times the weight it is carrying, which surely must be enough!