1977 GT500 – The Pain Continues !

Well – it has been a while since I’ve done an update here, but that doesn’t mean I haven’t been busy ! The 1977 GT500 rebuild has been moving along slowly, interrupted as sometimes happens by real life events that had a higher priority,  as well as just long delays in sourcing parts and sorting out issues related to the build itself.

The engine is back together after Joe at RPM Services in De Winton rebuilt the crankshaft for me and also bored the cylinders – but now I think I may have to take it apart again as I think a thrust washer is missing from the oil pump drive shaft. There was only one in each of the two engines I dismantled, but a close examination of the parts listings actually shows two of them and as the engines had both been apart previously by prior owners I don’t know for certain whether it was a late change by Suzuki to move to having just one, or whether one was just lost on both engines during previous rebuilds. It seems odd to me that both would have had the same washer lost – but then both engines had other things incorrectly assembled so I will double check just to be sure.

The other thing I have to do is repair the oil pumps – both that I have need new oil seals and those are supposedly in the mail to me and should arrive next week. These pump seals of course were not offered by Suzuki as the pumps themselves were not intended to be repaired, so some sleuthing has been required to figure out what will actually fit and where to buy them. As well, owners of Suzuki twins with oil injection from this era often report air leaks in the oil injector lines. Unlike the triples, the twins use a split feed line between the pump and the point of injection, and it seems that after 35+ years. what ever Suzuki used to glue these together is starting to fail, or possibly it is just hair-line cracks developing. Whatever the case, I am putting a drop or two of epoxy on the joint areas (marked in the photo to the left), and will also be flushing out the lines with methyl hydrate to make sure the check valves at the end of each line are also working properly. The same check valve design is used on the Suzuki triples and care must be taken to not damage the seat or small spring so blowing these out with compressed air is a recipe for disaster as new ones haven’t been available from Suzuki for quite some time.

The tinware is all in to Cycle Mania Artworks in  for paint – I expect that should be back before the end of May, but we shall see. I’m doing the bike up as it was originally when sold, so gloss black, with satin black and then more gloss black – not what I’d call exciting, but it will have the correct striping in cyan blue and gold which will add a little bit of flash !

I have recovered the seat using a kit from Pit Replica in Thailand. As I think I’ve mentioned previously, I sent them an original sample and they now offer GT500 seat covers specifically to fit the 1976/1977 model years as they are different from either the T500 covers (too narrow and wrong length) , or the GT380/GT550 covers (same seat pan, but the GT500 doesn’t have the cutout for a seat lock as the seat is just bolted to the frame).  The cost is reasonable and the quality is acceptable.

I am still trying to decide if I’ll use the correct stand-offs for the rear turn signals as I think they stick out too far. I can see me catching the left rear signal with my leg every time I try to get on and off the thing, but we will see what it all looks like when I’ve finished putting on the tinware and have the engine re-mounted in the frame.

The other issue I’m playing with is what to do about the front brake. Suzuki used two different suppliers of front brake components for this model (and for other models too of course), but no longer supply all the bits you need to repair the ASCO callipers. For the master cylinder, which is also ASCO, kits are available. The only difference from what was originally installed and the replacement appears to be the shaft that the brake lever pushes on is a larger diameter on the new kit, but everything else seems to be the same. For the calliper however, there is no longer a full ASCO kit available although you still can buy the seals individually. The calliper piston is not offered. After doing a bit of checking, I’ve decided to use a calliper piston from the GT550 Tokico supplied calliper as the bore is identical to the ASCO cylinder housing. The only differences I can see is that the the Tokico piston is perhaps 0.4 mm longer in overall length, and the groove for the dust seal is different. I’m hoping that the difference in length will not mean that I’ll have trouble remounting the calliper housing on the rotor with the new brake pads, but I’ll cross that bridge when I get there !

I have new rubber, new rear wheel bearings, new rear brake shoes and a shiny rear wheel already mounted. Today I’ll be working on the front end replacing the fork seals, the front wheel bearings, front tire and doing a bit of metal polishing.

One small step at a time !!

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