The GT550 Lives !

For those who have been following along, the engine started up almost immediately and I took it out for a short ride today. It sounds good, no ‘bad’ engine noises at all after about 20 miles so I think I’ll call this one a success. There is still a lot of snow on the ground – I have about a 1 metre pile at the end of my driveway for example, but there is lots of snow elsewhere on the sides of the roadway and people’s yards as well, although the roadways are generally clear. The air is a bit brisk, but the real worry is all the sand and small gravel on the roads from the winter as they have not been swept yet, plus as the temperatures drop quickly in the evening things like sewer covers can get quite slick.

One minor problem I had during the first few miles was the turn signal switch which seized up solidly. It had been a bit tight when I was testing it, but I thought it would loosen up with a bit of use. After disassembling the mechanism, I found nothing wrong with it mechanically and so just lubed it up with some dielectric grease and it now work fine.  At any rate, the plan for the next while is to gradually put some mileage on both the GT550 and the GT750 project bike  over the next few weeks, and to see what else shakes loose, or needs to be adjusted before taking either bike for longer runs.  I also have a few additional photos etc. to go up on the GT550 web site, as well as a short list of minor updates so that will keep me busy also.

With a bit of luck, I may be able to show them off at the CVMG Bike Night sometime in the next few weeks - all we need is some warm weather !

GT550 Rebuild Continues

Following on from my previous post on my Suzuki GT550 rebuild, it seems that luck is in short supply as I am still waiting for a couple of seals to arrive.  For whatever reason, there seems to be an inordinate number of basic things just not available for this specific model – like an o-ring for the starter motor for example which Suzuki has rather unkindly discontinued ! I have one coming from an NOS parts supplier in Toronto, and while I likely could also have matched one up from an industrial parts catalogue if required, it all just adds time to the process.

While waiting for things to either be located, or if located for them to be shipped I have gone ahead and assembled most of the engine – while doing so, I noticed that in addition to revamping the clutch assembly Suzuki had also changed the gudgeon pin design. The piston failure in the centre cylinder seems to actually have started with the gudgeon pin cracking in half, and so I was pleased to see that the new pins had a much thicker wall, as can be seen in the photo to the right. Presumably then, the failure my engine had was not an isolated event !!

I realise I said this in my post of March 20th, but if everything goes according to plan, I may have the engine in the frame this coming week, possibly in time for April Fools Day !! 

GT550 Starter Clutch

The new style clutch basket and starter drive assembly has arrived for the 1974 GT550 I’m rebuilding, together with most of the seals, gaskets and other bits and pieces I need. I managed to track the starter clutch assembly down in the UK from Suzuki-Dave who is a member of the UK Kettle Club, and from whom I’ve bought other items previously. Tracking down all the other seals I needed has taken some time, as some have not been available from Suzuki for quite a while – for example the oil seal that goes behind the drive sprocket ( 09283-25050 ) I finally sourced from a dealer in New Zealand. Most of the crankshaft bearings and the connecting rods are no longer available from Suzuki either, so I’m hoping that the crankshaft I have will be OK. 

I spent a very pleasant day up at Fred’s earlier this week washing the engine cases in his parts washer, and they are now look much better. I also rinsed out the crankshaft assembly just to try and flush any remaining small bits of aluminium off the big end bearing etc., and that all looks pretty good as well. As my wife is out of town this week, I very seriously thought about washing the crankcase halves in our dishwasher – this has been done by a number of folks and supposedly works well, however my guess is that they are all single (or divorced) so in the end I decided that I’d better not push my luck with SWMBO’d.

As per Suzuki Service Bulletin #GT-26 of August 15, 1975, the new starter drive assembly ( 21200-34820 ) was introduced with engine number GT550-63692 and is quite different from the older style, as can be seen from the photo to the right – the new style is on the left side of the photo with the new starter clutch gear above it. These assemblies come as matched sets and per the bulletin must be replaced as a unit. Of course none of these parts are still available from Suzuki, so anyone restoring these engines will likely have to take their chances.

With a bit of luck, I should have the engine back in the frame by mid week,

The 1974 GT550

Some time ago, I picked up a 1974 GT550 which came to me with the engine stuck. As a part of the deal, I also was given two donor bikes of the same model, but different years. Basically, the bike was complete, and just looked too good to pass over even though the cost to repair was probably going to be more than its value. As I did with my GT750 project, I’ve started a web site to capture additional details as the repair work on this GT550 progresses.

As was often the case, the donor bikes had been left outside with the carbs and exhaust pipes removed, so water, snow and whatever was blowing by had made their way into the engine cylinders and they were solidly stuck and not looking very good at all – as per the photo to the left.  After letting the engines soak for several weeks with penetrating oil,  I pulled them apart to see what could be saved, Interestingly, both donor engines appear to have failed due to holed pistons, so naturally I was curious whether the project GT550 had the same problem. As well, I had been told that this model of Suzuki had a fragile starter, but when I pulled these apart both donor bikes showed no sign at all of problems. One of them even still had its starter motor fitted, and when I’d pulled it out, I tried it with a power source, and it spun freely.

At the end of the day, I had about one and a half engines with serviceable bits and pieces suitable as spares – one actually had a set of first over pistons which are quite rare to find now. The barrels were in rough shape, but at least could possibly be bored out, and one set of engine side covers were worth keeping    

The next step was to strip down the project bike and see what its problem was. As it turned out, it had more than one. Once the head was off I was initially relieved to not see any holes in the pistons, however the centre cylinder had a lot of small metal particles on the top of the piston as well as in the exhaust port, and once the barrels had been pulled off it was clear where they had come from per the photos below left and centre. The centre piston’s gudgeon pin had snapped, and then the piston had essentially self destructed. The bits falling down from the broken piston were lodged between the crank throws and the case which was why the engine wouldn’t turn over. As well, when I pulled off the clutch basket, the starter clutch assembly basically fall apart as the centre boss had come completely apart. In the photo below to the right, you can see the broken one to the left, and what it’s supposed to look like to the right.   

Suzuki completely redesigned the starter clutch assembly in 1975, the year after my bike was built and obviously the updated version had never been installed.  The service bulletin which details the changes and new part numbers is GT-26, dated August 15, 1975 and a copy can be found here. I have two ‘good’ old style starter clutch assemblies from the donor bikes as neither of them had been updated either,  but I wasn’t too happy with doing this as I could reasonably expect the same failure mode again at some point – and as I was putting this on the road for my wife, I doubt she would be impressed if it quit working !

I am looking to see whether I can track down a new style starter clutch assembly and we’ll see what happens. At the moment, I’m waiting on parts, seals and gaskets before I start to put the engine back together