TZ250W

At the end of the 2003 season, I bought a TZ250W (1989). As with the powervalve, it was in a bit of a state and needed a lot of work to get it trackworthy. The bike had not been raced for a number of years and after its last race had been put straight in the garage and not touched since.

When I went to look at it with a view to buying it, we started it up so that I could hear it running. Everything appeared to be fine, the only obvious problem being that the powervalves were not working properly, either due to the ignition box being faulty or the powervalve motor itself. The motor was due a rebuild including the crank, however the spare crank was unused since its last rebuild.

Having got the bike home, the first thing I did was to have a look at the powervalve problem. As I still had Budge’s bike, I swapped things over till I found the problem which proved to be the ignition box. Rather than just go out and get another, I pulled it apart to see if I could find any dry solder joints or faulty components on the circuit board. Unfortunately, I was unable to find the problem, however I was able to source a used ignition from a TZ250A (1990), which is meant to have a better ignition curve and also does away with the battery.

Next job was to strip the motor. The very first thing I did was to pull the pipes off the bike. To my horror, there was a large amount of rusty metal flakes sitting in the exhaust port of each cylinder. This had obviously been dislodged from the inside of the pipes when we had started the bike up when I went to look at it and had then fallen back down and into the cylinders when the engine was stopped (As this is one of the reverse cylinder TZ’s, the pipes exit out the back of the engine and up through the tail piece). Luckily this had not done any damage to the cylinders or pistons, although a little had got onto the crank main bearings. As the crank was due a rebuild anyway, this was not a big problem. Next I started on the gearbox, which produced more horrors! When I drained the gearbox oil, I found that it was grey with alloy. The oil strainer was also full of debris. This was due to one of the bolts holding the gear shafts in coming loose and threading it’s was out till it hit the big primary gear. The primary gear had the sheared the top of it and dragged it round and round removing quite a bit of metal from the plate that holds the ‘box in place. Apart from the metal removed from this plate there was no other serious damage, and luckily there was not enough metal worn away to weaken the plate significantly. After a major amount of internal cleaning, I was able to get the motor reassembled and back in the frame, so that I could test the new ignition which had just arrived!

Having ascertained that the new ignition was working alright, I pulled the engine out again and stripped the rest of the bike down right back to the bare frame. This was so that I could get one of the fairing mounting lugs repaired. It was cracked where it was welded onto the frame and also split down its length. While the frame was bare, I could also clean it and inspect it properly for any other damage. Fortunately though there was none.

By the time I started putting the bike back together, the 2004 season was rapidly approaching. Two weeks before the first meeting I was horrified to find that the rear suspension linkage bearings were all well and truly shot. I immediately ordered new ones, but they had to come from Japan and thus I did not receive them in time. This presented a bit of a problem as there was about 5mm of play at the end of the swingarm with the old ones in. Andy Burke came to my rescue again. He made me some aluminium bushes in place of the bearings. There was a fair bit of stiction with these fitted, however they did eliminate the free play.

You can read how I got on at the races in my race diary section.

After the first meeting there were still lots to do. The first being the wheel alignment. The standard chain adjusters on the bike have very poor wheel alignment brackets. So poor in fact that it is impossible to line the wheel up accurately with them. Using two long straight metal bars, I got the wheels perfectly in line, then measured the distance from the back of each chain adjuster to the ends of the swingarm and noted the difference which turned out to be 1mm. Now all I had to do was use this measurement whenever I adjusted the chain, or changed wheels.

With wheels now in line another problem appeared. The chain was fouling the tyre badly. I was able to space the sprockets out to allow the chain to clear the tyre. I was not sure if doing this would cause any further problems and the only way to find out was to try it out on the track.

At the track I found that the rear sprocket bolts were come loose very quickly. Even with an application of loctite they were still coming loose after a couple of sessions. At the July meeting, one bolt had come out so far that it had started hitting the swingarm. There was not too much damage, however I had the same problem again in August which resulted in a badly damaged swingarm. At the time of writing the swingarm is away for repair and I am trying some other mods to keep the bolts from coming loose.