Of plastics and powerplant!
Ralph is sorting the bodywork and motor on his little trailie. What does he find?
Iam continuing to put every non-working, non-drinking waking hour into the diminutive trailie bike. Why, I’m not really sure, as I have never owned a trail bike in my life, so can’t be reliving my misspent youth and believe me, my youth was seriously misspent. I had big four-stroke road monsters, which I rode as though competing in the TT; fearless in the safe knowledge that I was immortal, as all young bikers are. For a short while I had a Bultaco Sherpa trials bike, but I could never get the hang of it on the dirt; it just spat me off backwards, regardless of gear selected and was a sod to restart, given the insane left-hand kick start; are Spaniards all left footed? I sold it off to buy an IOM Steam Packet ticket! Anyway, less of my waffle; all the plastic parts on the bike were mired in the mud of a thousand fields and lanes, so needed a good clean. I gave all the parts a decent scrub with a wheel brush and a bucket of soapy water. Like every other part of this poor bike, the air-box has been the victim of someone with more power tools than knowledge, as well as cruel neglect. It has had various bodged repairs and had either been ridden in a warzone, judging by the random rough holes in it, or attacked by someone with a drill enjoying an acid flashback. The first task was to remove all the steel brackets from the plastics, which are riveted in place. It’s not a hard job to do; just make an educated guess at the rivet size and drill through the centre of the rivet. If you’re not sure of the size, drill the first one a size down, you can always go up a size later. Most rivets on bikes will be 3, 4 or 5mm as a rule. Once removed and cleaned up with either a visit to the blast cabinet or the wire wheel, they got added to the bucket going for zinc plating. I do sometimes do my own plating but, to be
honest, it’s quite a fag and is rarely on a par with that done by the professionals: check out the services ads in this issue of CMM to find a good plater. I have no idea why the air-box had so many seemingly random extra holes, but as it wasn’t in Mr Yamaha’s masterplan and given how successful the bike was for a number of years, I’m going with the original design, which means I had to fill the holes up. As I often have to repair bike plastics, I have invested in a not inexpensive professional plastics repair kit, as an alternative to plastic welding. There are pros and cons for both methods, but for this job I favoured this kit. I had extraneous holes in the side panels and used some five minute epoxy glue and some West System woven mat I had kicking around, but more on that in a later edition. I chamfered both sides of the holes with a small burr in my Dremel. On the outside I taped release film over the holes and on the inside I roughed up the surface where the adhesive needed a key to bond, with emery cloth. When most plastics are moulded, the inside of the die is coated with a release agent that remains on the surface of the plastic after manufacture. If you want to stick anything to it at a later date, it is crucial to remove this first and the easiest way is to rub it away with an abrasive paper, which you have to do to give it a key anyway. I then sprayed a thin coat primer over the areas to be bonded. The adhesive is a two part product that requires thorough mixing before use. It comes in dual tubes, where both ingredients are squirted through a special disposable mixing nozzle with a purpose built application gun. I pumped out enough glue to fill the holes and give a good coating over the area, before pressing the reinforcing mesh on top of it, which also presses the glue through the holes and expels any air. Once the bond started to go off a bit, the releasable backing film of the mesh was peeled off and more glue squirted on which I then tooled up with a plastic spatula from West System (purveyors of epoxies primarily for the marine industry). The last hole on the corner was also filled with the plastic adhesive and the broken off lug bonded properly to the previous partial repair. Once the glue had gone off, I peeled off all the masking. As you can see in the photo, the adhesive has pushed the release film off a bit, and if this were a cosmetic repair I would rub it back with varying grades of wet and dry, before painting, but as this will not be seen I am leaving the extra thickness for better strength.
Once the zinc plating returned, I needed to replace the battery securing bracket. This was an easy job. Simply place in the right way around and fix it with pop rivets. I chose alloy rivets, as steel ones a) rust and b) require a lot of force which might have damaged the plastic of the air-box body. Just above the bracket at one time was a strip of medium density foam to cushion the battery. There was just enough left of this to prove its previous existence, but not enough for it to fulfil its remit. I removed what was left with a sharp wood chisel. Then I dug around in the workshop and found some self-adhesive foam I was saving for such an occasion. I cut a suitable strip with a steel rule and a scalpel. After a thorough degreasing and keying up with wet and dry of the area, the strip was applied with firm finger pressure. Having taken all the cycle parts to pieces, I next turned my attention to the powerplant. It really didn’t look great, and it wasn’t about to get any better with surgery. While I’m no Stan Stephens, even I know that it’s a piece of cake to pull the top-end off a stroker… or is it? The head came away with little fuss. Six nuts flew off and the barrel appeared to be held down with four bolts. In my ignorance I assumed that they were steel bolts. The first three undid with little complaint, but the fourth was as tight as a gnat’s chuff and wasn’t moving. Using a six point impact socket I offered it up to the Lord Air Impact wrench which immediately spun it loose: or so I thought. What it actually did was to re-form the hexagonal head into a round form. At this point I realised that these were aluminium
sleeve nuts. I bought several sets of expensive ‘buggered nut and bolt extractors’ and the only one that would fit down the hole was the sort made to fit in a ¼in hex driver impact wrench. Like a lamb to the slaughter, I fitted the correct extractor into my ridiculously expensive Makita impact driver, bought on a whim when I felt flush (I am very much a tool buying addict, turned pusher to help support my own habit). The bit sheared off in the mouth of the £300+ Makita and I couldn’t get it out; eventually having to return it to the main dealers, where much to my relief they managed to extract the offending lump of carbon steel from it. As the extractor had clearly bitten well (too well) into the offending sleeve bolt, I thought that the obvious way forward was to fit a ¼in socket on top of the extractor and use a biggish breaker bar with a series of reducing adapters. I also carefully applied some heat to the offending item. This time it sheared off what was left of the ‘head’ of the sleeve nut. I’m normally pretty calm around the workshop, but I was now boiling over, anger exuding from every pore. There was only one thing for it – oxy-acetylene, and lots of it! It was tricky to say the least to get the uber-heat where it was wanted without damaging anything else. I was actually going to cut away what was left of the nut with a cold chisel, but with the nut being not far short of white hot, it finally gave in and started moving. Only a tiny bit at a time mind, but once it was properly moving I cut a curf in the top with a chisel and managed to unscrew it. Once the barrel was off it was obvious what the issue was; some idiot had fitted an incorrect stud in the top of the crankcase, sawed a bit off and then jammed the nut on with the force of a gorilla on steroids. I guess if it wasn’t for motorcycle abusers then my engineering talents would go to waste.