King of the IT crowd
Put two off- roaders together and the first question from either is generally “What’ve you got on the go at the moment?” This is often followed by “You’re doing a WHAT!?” Occasionally it is “Oh, one of those…” but more often it’s “You must be mad”. You ch
Assembly progresses as a problem is solved and more information comes the editor’s way.
To be honest I thought I’d be riding this IT465 by now but hey ho, that’s the way things go sometimes and unlike our last few project bikes where spares have been plentiful, the IT range has gaps in it. Okay, people are working to fill these gaps but it can still be a long process to source bits but there were enough bits to make a rolling chassis for the International Dirt Bike Show stand. The IT promoted quite a bit of interest on our stand and a few people did say they’d got bits and pieces left over from their own rebuilds, including a lad who reckoned to have a replacement lower front curve for the exhaust pipe. If you’re reading this… still interested in the pipe…
One of the bits taking forever to source was the small bearing on the end of the selector drum. In the bearing world that one doesn’t have a particularly hard life, unlike a wheel bearing, which spins whenever the wheel moves, this selector bearing has to move when the gear pedal is pressed and, as such, is not noted for wearing out. But our engine has suffered a bit through lack of maintenance and the… well I was going to call it oil but that would be stretching it a bit… sludge in the gearbox casing had done its worst and even when still on the shaft, the poor bearing felt rough. Once off the shaft and rinsed through in the parts washer to get all the crud out it didn’t feel any better, even soaking it in oil didn’t mask the roughness and I stopped kidding myself that it could be reused. I had to convince Nick Scott at Motoduro that this bearing was worn out… he thought I was joking “…but it never wears out?” Ours has…
Once the bearings were all in the workshop I could lay the cases out, warm them through and drop the bearings in place. Once upon a time a gas blow torch would have been used to heat the cases up but these days a hot air gun is a safer option, even if it may take a little longer to work. The old test method of once spit bounces off the metal being heated is still a good indicator of when the cases are hot enough. Once up to temperature and with the bearing still cold it will be an easy job to press it into the hole without resorting to any hammers and drifts. Once the bearings are in, leave the cases to cool, though I suspect in a professional workshop things might be a little different, as they have to earn a living rebuilding things, whereas I’m doing it in an amateur way.
While the cases cooled I laid out the gears and selector drum and referred to the manual and the stripdown pics to see where everything went. The cogs on these shafts are held in place by a series of circlips and it could be easy to lose the sequence they’re on their shafts so I took plenty of pics and referred to them as the cogs went back on. A visual inspection of the cogs and shafts showed they were okay, no chipped teeth or anything like that and once through the parts washer they were rinsed and dried, then oiled and were ready to go back into the case. Most motorcycle engines have a particular assembly method suggested by their maker and it makes sense to follow this, as life will be easier. In the case of the IT465 the right-hand case is laid flat and all shafts and the crank are inserted into it, then the left-hand case is fed over the top.
The image in the official Yamaha manual for the IT465 shows a scrupulously clean work area and an engineer in pristine clothes working on a support jig specially made for the job. In our workshop the bench was swept clean, then a rag soaked in oil was wiped over the surface to pick up all the other bits and pieces of muck before a slightly more organic support jig was used to lift the case face off the bench top. The crank end would hit the worktop otherwise. For our engine I used some 100 x 50 dressed softwood and drilled a couple of holes for some round bar to go in, which stopped the case dropping off the support. To cut the dust I wiped the wood with the oily rag again and assembly was relatively simple. I did have to use a puller to make sure the crankshaft went in the main bearing fully but it all went smoothly and the mating faces of the case had a light smear – and I mean a ‘light’ smear – of gasket cement.
It is a narrow margin between enough cement to seal and too much so it squirts out. I once was asked to have a look at an engine that had stopped working and the answer was obvious as soon as I saw it… seriously this engine had orange gasket goo coming out of everywhere and looked as if it had been ladled on with a trowel. Early in my days of doing my own maintenance I was quietly told nothing beats a flat mating face and the lightest smear of instant gasket for sealing. What a lot of people seem to miss is if the goo squirts out and is visible on the outside, then it will do the same to the inside, which can get in oil ways.
Just because it came off that way doesn’t mean it was right. The swinging arm on the 1981 IT is taken from the previous year’s YZ and is a strong but light construction with steel bushes, stops and bearings pressed in. To fit to the frame the swinging arm ears go either side of the engine and there are tubes that clamp up when the spindle passes through them, while the frame and engine and face bearings provide a measure of centralisation. At least that’s the theory but try as I might there was no way the assembly would go back in as it was when it was stripped out. I couldn’t figure out what was wrong. I had pictures of the way it was when we got the bike, but not only could I not get the new bearings to go in, the old ones didn’t go in either, yet there they were in the pics. In the end, just for display at the show, I didn’t bother with the face bearings and actually determined something was wrong with the original assembly.
It was only when I got an original schematic drawing of the assembly that
things became clear. Whoever had been responsible for maintaining the bike in the past had managed to get the face bearings between the swinging arm and engine… this must have taken an awful lot of force and probably some kind of jack to spread the frame enough so the bearings would go in.
With a drawing available and all the bits laid out on the workbench it was obvious there were a couple of bits missing from the original set-up. Already purchased was a bearing kit that has the needle roller bearings, new shafts and the nylon bushes, plus the seals that go on either end. Missing were the steel bearing covers, which are also part of the distance pieces. Thankfully, Motoduro stocks them and it also does new bottom mount bushes in stainless steel and snail cam stops in the same stuff. With the new parts looking all smart and non-rusty, the actual swinging arm itself looked secondhand and could do with a clean-up. The original lacquer finish had been worn away and there was some corrosion under the bits that remained. A while ago I found the acqua blasting finish to be more than acceptable as a final treatment to alloy, it gives a satin finish and is easily maintained. Sort of localish to us is the Aqua Blast Center at Doncaster and its cabinet will happily accept something the size of the swinging arm.
Once cleaned and back in the CDB shed it didn’t take long to press the bearings, bushes and stops back in and now the swinging arm looks good.
With the schematic diagram on hand to show the sequence of parts, all should be well with assembly.