Well, it was a good plan. I had bought this Yamaha XJ650 turbo to use despatching while I stripped and renovated my XJ900 that had been all the way round the clock but was getting a bit smoky. The Turbo's fairing was keeping me nice and warm during January and I was more than a little miffed to discover that along with its new whirring noise the engine had lost the ability to change gear and was stuck in first. I took it back home and got old faithful out - the XJ900 did eventually start.
A couple of weeks later I started stripping the turbo. A task I was dreading. The fairing comes off quite easily, so do the carbs, airbox, battery holder and many miles of various pipes... No, what held true terror for me was the actual turbo unit. This highly technical piece of Japanese wizardry had over the years been reduced to a well rusted lump - I suppose that's what comes of living underneath an engine and getting heated up to red hot and then dunked in road slime thousands of times a year, year in year out. I felt sure that if I so much as touched it with a spanner it would crack up into several pieces.
In the end, I sussed that it could be left in the frame if I removed the pipes that fed into it. So, I went to get my crowbar, possibly the best tool I possess, made of really strong steel that no matter how I bash it won't break. After a fair amount of huffing and puffing the pipes popped out. By then the rain was really coming down so I went in and spent what was left of the weekend doing more pleasant things. A shame really, because it was even wetter and colder the next weekend.
I didn’t go near it on Saturday but on Sunday I woke early, it was by then almost February. I put on my oldest clothes and stoutest boots in readiness to tackle the super tight nuts and bolts of the shaft drive and engine mounts. While every sane person in the world slept, I was out-there doing it. By lunch time the lump was only held in by its own mass. I was going to enlist some help but by then the red mist had settled, and anyway the oil leak it'd had before and my shameful lack of machine cleaning meant that anyone pressed into aiding me would probably hold it against me for life, so I did it all myself, although I'm only little.
What I did was kick the bike over then got a jack underneath and with the help of my trusty crowbar out it popped. In fact, it popped out so fast it almost pulped my foot on its way to the gutter. It did manage to smash a long bolt that stuck out of the front of the engine — later, when I found out that this was the anti-knock sensor I thought that it was a pity that it hadn’t sensed the knock coming because it could have warned me. I dragged the engine on a plastic tray down the alley and into my shed. It would have been much easier to have gone through the house, but also most certainly fatal.
Once in the shed the dismemberment really got going. I didn't have a manual for the turbo but the Haynes one for the XJ650/750 covers most things. As I pulled each bit off I placed it in a plastic bag, labelled it and put it somewhere safe. I was being meticulous. I am not known for this but as this was the first engine I've ever ripped completely to bits I thought I would make the effort. I was being ever so good and then disaster struck.
While attempting to get the alternator bolt out I failed to make sure the crank could not turn. I pulled on the spanner, the crank spun until it was stopped by two piston skirts coming up against the crankcases....ping, ping. I was by then a couple of pistons and an anti-knock sensor down.
Still, the rest of it went OK. The problem, as I suspected, was that the rubber guide that tensions the primary chain had disintegrated and the bits had fallen into the gearbox. No damage had been done (if you discount my ham-fisted handling). The cost of replacement bits was well out of order. The head and base gaskets were £20 each, a piston was £60 and if I wanted a new anti-knock sensor that was around £80. In the end I just bought new gaskets and a used set of barrels that came with sensor and pistons.
I rebuilt it and could not sleep. Had I put too much gasket goo on where the two halves went together? This was so much on my mind that | stripped it again. Yes, I had. The next time I put the engine together there was a gasket dowel and an O-ring left over. Had they come with the barrels from the breakers? I lay awake thinking about that too, so I took it down again and found that, yes, they were spare ones.
Finally, as spring threatened to encroach, it was ready to go back into the frame. I enlisted some help to put the engine back in. Another weekend saw it all back together. It worked, after a fashion. The turbo refused to cut in. I put this down to big leaks in the joints between the down pipes and the unit. At least all the gears were there. I went into work on it, 30 miles later it went sick and refused to start. The battery was already low, then while it was cranking over it made a funny, desperate noise and stopped. I may not know a lot but I know when an engine’s seized.
I sent out a call to the rescue services. When the man showed up he insisted that it was just a flat battery and had to connect it up to his super battery and attempt to get it going. It did run, with the most horrendous noise, and then the bastard revved it. Quite honestly, if I had had something in my hand I would have hit him with it. He pissed off and I waited for the van to pick us up; it was a long wait. Once home, I got the XJ900 out again.
It was a while before | got around to the Turbo again. It was very tempting to just ring up a breaker and get rid of it, but in the end I took the engine out. And I found that it was only a bolt coming out of the starter clutch that had caused the grief. I gave it a brand new starter clutch and a new camchain, whacked it back together again, threw the engine in and used it for a whole week.
I wish I could say it was perfect but it wasn't. First of all, the turbo was not cutting in - I put this down to the leaks and the paste being being blown out. Then it started to cut out on two of the cylinders. I put this down to a coil dying and sent off for one from a breaker. About this time my brother showed up, who I gave the Turbo to as I owed him some money. He put the coil in and ran it for a month or so and even did a day trip down to Plymouth before giving it back to me, saying something about it being the worst dog he had ever ridden. And I have to admit he had a point, or ten. By then it had taken to leaking oil out of the top of the forks as well as the oil seals. The brakes didn't work and the engine kept cutting out every time it got hot.
I stripped the forks, filled the pits with Araldite and put new seals in plus new O-rings at the top. | also stripped the brakes and made them work. The bike rode a lot better, which was just as well because it suddenly became my only machine. It was still cutting out until I disconnected the anti-knock sensor. I think this was happening because the turbo was not forcing charge into the cylinders at high revs when the engine thought it was going to pink it retarded the ignition, making the motor act as if someone had just put the choke on.
With the anti-knock disconnected it went OK, and it would creep up to an indicated 100mph but still the boost gauge was reading zilch. I phoned around and located some good condition down pipes. When they arrived I put them on and they fixed the exhaust leak. I reconnected the anti-knock and went for a blast. It was good, lots of power, the turbo definitely working but still nothing on the gauge. Back home, an investigation turned up a little pipe that was not connected to the black box that works the gauge.
Another trip showed that at last it was fully functional, and today I did more than 200 trouble free miles. It only took nine months, much gnashing of teeth and hundreds of pounds... it was interesting but I’'m glad that's all over now.
Max Liberson