Engine and Transmission

As always there is a story to go along with any rebuild and knowing the ‘why’ of what caused a vehicle to be parked is always of interest to me. In this case, while the bike appeared generally complete, nothing happened when the kick-start was tried – as in it obviously spun over the gear box, but that wasn’t in turn connected to the crank shaft. Once I had the side cover off, all was revealed !

My best guess is that something had impacted the side of the engine case – the clutch basket was broken (indicated by the upper arrow) and the lower arrow points to a section of the crankcase that has been broken and a chunk of aluminium is actually missing. There are no signs of damage to the right side cover itself, so I have to assume it was replaced, but for some reason the rest of the damage was not addressed.

The early Suzuki T500’s had a design flaw related to the oil capacity in the crankcase which was addressed in Service Bulletin T-3 issued in December of 1973. This factory change increased the oil capacity from 1200cc to 1400cc and so addressed premature failure of the 4th and 5th gears, which had been happening since the T500 introduction in 1968. Initially the fix was to install a rubber dam (part number 99104-08800), and then starting with the ‘L’ models the casting was altered and the overflow weir was raised by 10mm. My casting needed to be welded as it was missing a chunk on the underside anyway, and so I took the opportunity to have a raised weir installed at the same time. For this, I fabbed up a small strip of aluminium and had it tack welded in place.

The case repair on the underside turned out really well  – it is visible, but could be hidden if I were to paint the case. As the original factory spec was just bare cases and also as the repair is on the underside, I’m not going to do much of anything to it as I think it looks fine as it is.

In the boxes that came with the bike was actually a lot of information covering the period from 1975 through to 1982, and it appears to have been well cared for during that time. There were receipts for new pistons and also a re-bore, so I knew the engine had been apart at some point.  With the engine pulled apart and laid across the bench, it was time to assess the wear and tear of the engine and transmission. The crankshaft and related bearings and connecting rods all seemed fine. You can do leak down tests on these engines to check if the seals are doing their job, but usually if when spinning the engine over you don’t feel any blow back on the inlet and do feel lots of suction, then the seals are likely in good enough condition for the engine to run. Replacing the seals is not cheap as the crankshaft has to be fully pressed apart, but as the engine is fully apart anyway, I’ll have it done.

The barrels are on first over, and were checked out by Joe at RPM, and I was pleasantly surprised to find that they were still within tolerance so I will just re-ring the pistons and have the barrels honed. The transmission was however another story.

As mentioned earlier, the engine had previously been apart – whether at a dealer or by a previous owner I’m not sure, but the transmission had not been re-assembled correctly and the splash plate had suffered some damage.

Likewise the output shaft needle bearing carrier on the clutch side had been installed the wrong way around and so that bearing had not had enough oil, causing the end of the shaft to be eroded away over time. The worn shaft is on the left in the photo and a good one is shown on the right. Luckily I had a complete, good spare transmission and rather than mix and match gear clusters and risk uneven wear on the gear tooth faces, I will just change everything over.

At the moment, I’m waiting on parts to arrive which is not likely to happen till after Christmas now – so I’ll move on to checking over the electrical system and controls.

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