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2. Engine

  1. Why
  2. Cases
  3. Transmission Woes
  4. Spline
  5. Injector Valves
  6. Cobra Project Menu

Why Was It Parked ?

There is a story to go with any object, and I'm always curious as to why a bike has been parked and then left to sit in some garage if its lucky, or someone's backyard and exposed to the elements if it is unlucky. 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 !

If you click on the image to the left, you can see a larger version of the photo. My best guess is that something had impacted the side of the engine case - the clutch basket was broken and the arrow points to a section of the crankcase that has been broken and a chunk is missing. There are no signs of damage to the right side cover so I have to assume it was replaced, but for some reason the rest of the damage was not addressed.

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. I'll have a better idea once I open up the engine for a closer look, but most of the work at this moment appears to be cosmetic, with the exception of the clutch and crankcase damage which will be easy to address.

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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 so on with the next step !

Transmission Woes

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 was 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.

The engine obviously 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 tooth faces I just changed everything over.

The crankshaft was rebuilt for me by Joe down at RPM in Okotoks who also bored the barrels to first over. With those parts back and all the bits in the case, I was ready to button the engine up.

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I wasn’t happy with the state of the spline on the shifter shaft – from a modern day perspective, the early T500's have an odd set-up in that you have the option of installing a right or left shift lever or brake arm. Specifically the shifter shaft extends the full width of the crank case and side covers with a spline on both the left and right sides – normally the gear selector lever in Canada is on the left, and so the left side splines are often worn badly as can perhaps be seen in the photo . But the splines on the right side are normally pristine having never been used, and when new at least were covered with a rubber cap which further protected them from damage. Later model years just had the left side spline and the right end of the shaft was shortened by the amount of the right side spline. However, for whatever reason (likely cost), Suzuki elected to not modify the right side cover, and so the hole where the shaft used to protrude together with its oil seal was left right through till the end of production in 1977, with just the end of the sad little nub of the shortened shaft still visible.

As may be imagined, good usable early shifter shafts are hard to find, but the later single ended ones are more common, and I was able to locate one in very good condition. But how to make it look like the double ended early style ? Luckily Roger, who is a friend of mine and who is also in the local CVMG chapter, very kindly offered his help and the use of his lathe to make the required modifications ! Roger usually works on older British bikes, but does own a modern Ducati as well as an older Honda and he finds having a lathe very useful for making specialised spacers, bolts and fittings as required. Having the tools to make your own missing bits when you have to is sometimes the only option, with the potential added benefit of also allowing you to subtly upgrade selected mild steel fittings to stainless if desired . And referring to the photo – in case anyone is concerned, Roger was wearing safety glasses once the set-up was finished and the machining work actually started.

What we (actually he) ended up with was a threaded hole in the right end of the shifter shaft and a turned fitting, that extended the newer style single ended shaft out the right side of the engine cover. The end of the fitting is recessed so that the bolt head is not visible when drawn up, and the whole things is long enough to accommodate the reproduction rubber cap that I picked up from Reiner in Germany (just email him at, and ask him for a list of the parts he has available) .

It looks pretty good I think, and other than myself, Roger and whom ever reads this, no one will ever know that it isn’t real !
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Injector Valves

One interesting feature of this engine was thta the check valves at the ends of the oil injector lines were rebuildable ! I only wish Suzuki had kept this design with later engines as it certainly would have made life a lot easier on the triples for example. At any rate, after disassembling them and giving them each a light clean-up they all tested fine so that at least was a bit of good news.

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