Suzuki Locks and Latches – Part 2

As mentioned in the last article, the GT750 tank filler cover lock as used on the 1976 and 1977 GT750 is a different animal. Unlike the other locks used by Suzuki, this one has a crimped bezel which retains the lock tumbler, making it a real pain to deal with. For this reason, a number of people (including myself) will suggest that you try to find a tank cover lock complete with key because it is then easier to make everything else match it, rather than the other way around.

Referring to the photo below (just click for a large image), notice that the lock tumbler itself actually only has one leaf. This means a range of different keys will open it, as many keys will have the same lift at that position on the key. I have three locks in my spares box, and one can be opened with a 140 and a 150 key, and another will open with the 207 or 150 key. In theory, if a person had enough different keys then you should be able to find several that will fit any given lock. I suppose at one time, there would have been markings on the barrels which would allow you to work out which range of key numbers fit which locks, however only one of mine has anything interesting stamped on the barrel and the others are blank. There are what appear to be different casting numbers on the end of the barrels, but these numbers do not appear to relate to which key to use. So if you are in the unfortunate position of having a tank cover lock, but no key then you are in a bit of a pickle.

The good news is that Suzuki still sells these locks under part number 44280-37010 for about $34 in USD in the USA or € 35 in most of Europe. For some reason they are seriously silly money at the one place I checked in the UK (£62 !!! ). As a matter of interest, the same lock is used on several models of 1977 through 1979 GS750, GS550, GS400, GS425 as well as the 1976 RE5. Given that the new lock comes with two new keys, a new retaining clip, new gasket and also given how easy it is to re-key the other three locks on a 1976 or 1977 GT750, this then really is the logical path to take if you want a matching set of keyed-alike locks for your restoration.

Of course, if you are a purist, then go ahead and re-key the one you have ! The only hard part is first removing and then re-fitting the bezel without damaging it. You can make your life simpler when re-installing the bezel and either saw tooth the inside edge of the bezel so that you have many small triangular tabs to fold over (the same trick also works on the instrument stainless steel retainer rings by the way) or cut excess material away with a Dremel to leave four tabs (as seen in the photo) which will make it much easier to re-crimp into place. The bezel, the tumbler cover and the trap door are made of stainless steel and so will clean up nicely with a bit of care.

Good luck !

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Suzuki Locks and Latches

I’m still waiting for the exhaust to be re-chromed on my 1972 GT750 project, and so rather than just stand around, I’ve decided to do a but more fiddling with the next project, which is a 1975 GT380.

One of the (many) little jobs to be done is to assemble a working set of locks and latches and for them to all be keyed alike. For the GT380 I have collected together a set of latches to be worked on as seen in the photo to the left (just click on the image for a larger version).  Re-keying these locks is not difficult if you have a spare one or two to provide you with a decent selection of  tumbler parts to choose from. Over the years, I have at various times described lock re-keying elsewhere on this web site, but I thought it time to gather all the information into one place for ease of reference. Note that normally, on the 1974 through 1977 models at least having the flip up fuel cap, you do not have to re-key fuel cap locks as any Suzuki key from that era should open them. The 1976/1977 GT750 is a different case and I may cover that later, but right now the focus is on the GT380.

The Suzuki locks of this era having the double sided key blanks, used a 4 different leaves (possibly 5 but 4 for certain) for their key combinations in the tumbler that the key is inserted into. These leaves are set into channels and in their normal state, are lifted into the ‘lock’ position by a tiny little spring under the ear of the leaf which is very easy to loose if you are not very careful. The act of inserting the key, just pulls the leaves down into a position that allows the tumbler that the leaves are fitted into to turn in the barrel. So to re-key a lock, all that is needed is to alter the leaves so that which ever key you wish to use will, when inserted, allow all the leaves to sit flush with the tumbler. The first thing though is to get the tumbler out, without damaging the mechanism.

We will start with the steering lock first.  Each tumbler regardless of whether it is for the seat latch, ignition switch or steering lock is held in the barrel with a locking blade at the rear of the tumbler. In the case of the steering lock, this locking blade is in a recess that Suzuki pinched shut as seen in the photo. To release the locking blade, you need to open up the slot, either by using a Dremel, or some means of prying the slot open. Having done so the locking blade may be lifted out and the tumbler will drop out of the barrel. There is a photo showing the disassembled steering lock near by. I use a bit of white grease on the locking bolt when putting the cleaned assembly back together and a bit of light oil on the tumbler. After testing to be certain the lock works properly, I reseal the locking blade either by pinching the slot closed again, or using a small dab of sealant just to hold it in place. Once installed in the steering head, it can’t fall out, so something like epoxy is not required.

For the seat latch, you need to first disassemble the rear of the latch housing by removing the two screws securing the backing plate. Having done so, the spring loaded latch arm may be lifted off its post. Under the latch arm you will see a pawl the slides the helmet strap retaining bar back and forth, There is a small brass spring blade recessed into a slot on this bar, so when pulling the bar out of its slot be sure to not loose this. Take a look at the photo nearby to see the spring preparing to escape. With the pawl out of the way, the spring loaded locking tab can be seen in its recess, and it just needs to be depressed using the blade of a small screw driver such that the lock tumbler can then be slid out of the front of the  lock barrel. A photo of the whole assembly in pieces is somewhere near here. I know a fellow in the UK who makes some excellent quality stainless steel components for these seat latches, plus a few other items. If you wish to add some bling to your latch, then his contact information is located here.

For the ignition switch, there is a hole at the rear of the lock barrel (indicated in the photo) into which you insert a pin to depress the locking blade, and then the tumbler will fall out of the front of the lock. Corrosion and the passage of time may make it reluctant to leave, so just work slowly and don’t force anything. Note that this release only works if the switch is in the ‘Off’ position.  Give everything a good clean, lightly oil the tumbler and put it back together again once you are happy with the key operation. While you are at it, it may not be a bad idea to open the rear of the ignition switch to give the contacts a good cleaning and some dielectric grease. It could also be a very bad idea. Just be aware that there is a load of spring loaded contact plates and ball bearings all waiting to make a dash for freedom under that contact plate, so if you do decide to do this, be very careful.

For the re-keying, I usually do these one lock at a time and with the tumbler removed, I just insert the key I want to use and see which leaves are not being retracted into the tumbler. These I then pull out (or in some cases push out from the under side) and substitute a different leaf having either more or less lift as required, such that all the leaves sit flush with the top and bottom of the tumbler when the key is inserted.I then give it all a good cleaning, lube with some light oil and put each assembly back together.

When doing these leaf swaps, there are just a three things to be aware of:

  • There are two styles of leaves. The older style has ‘pips’ on the side that lock the leaf into the tumbler, and the newer style of leaves do not have these. You can mix and match the different types of leaves, and if you have leaves with pips and are modifying a newer assembly, then just file off the pips. The leaves with pips normally have to be pushed out of their slots from the bottom of the tumbler.
  • Note that the newer style of tumbler that uses leaves without the pips has the annoying tendency to have all the leaves escape the tumbler if you turn it upside down which can result in loosing the tiny little springs. You have been warned !
  • The most important thing is to not loose the springs. If in doubt, do the disassembly inside a clear plastic bag so that if something does escape you at least have a reasonable chance of finding it. Disassembling the rear of the ignition switch inside a plastic bag is also not a bad idea, for the reasons noted earlier.

The last thing to note is that if you re-key the lock, then the key number stamped into the stainless steel cap on the face of the tumbler (later locks are not stamped – earlier ones are) won’t match the key that you are using. Because of this, where possible, I try to buy a key (there are several sources on eBay) that matches an available ignition switch, as that is really the only one that can easily be seen. The other locks (steering and seat), I just polish up and don’t worry about the number mismatch.

If all of this seems like a more work than you wish to take on, then there is a fellow I know in the UK who does offer this as a service (and no – I do not get a commission). You can do an internet search for Mike Yeadon to find him, or check the Kettle Clinic board in the UK (which is the second best source for free information after this web site 🙂 ),  or contact me directly via email and I will forward your contact information to him.

Good luck !

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Piping Hot – Addendum

A small follow-up to the exhaust pipe situation for my 1972 GT750 J rebuild. Although I did say in the previous post that I was finished with cutting open any additional pipes, I lied ! Given the cost of having these re-chromed, I decided that the small pipes I had available needed a closer look just to be certain the internals were all sound.

This photo (just click or tap to see a larger version) is actually of a later 1975 through 1977 inner, lower pipe, and again you will note that as with the other large later model pipes, there is an additional lead baffle plate (the one closest to the engine) which is spot welded on both the inner and outer skins, which prevents you from just slicing the pipe end to end and lifting off the outer skin. With this pipe, you can see that all the baffle plates that the removable baffle slide into are broken. They actually have rusted, and then broken away from the rear outer skin that they are spot welded to. The rear cone is spot welded to the outer skin on the inside only.

The interesting thing that Ross and I discovered, and that certainly I was not aware of, is that the small pipes do not have wadding under the metal sound deadening mesh at the front section of the pipe.  The large pipes have wadding, but not the small ones.  Both the 1972/1973 and the later style inner pipes just have a fine metal mesh, similar to screen door mesh, spot welded to the inside of both the inner and outer skins. I had been told by many people that wadding was installed in all the pipes. Having looked at several examples now, it is clear that this is true only the large upper pipes. That is actually a good thing as it means that concerns about neutralising the acid used by the plating company is less of a concern for the smaller inner pipes, as there is nothing there really to absorb and hold the acid. A good flush with water should be all that is needed.

The other thing I confirmed is that the first baffle plate (the one nearest the engine) does indeed differ between the J, K and L pipes and those from 1975 and later M, A and B models. As seen here, the later style inner/lower pipe has a outlet diameter of 20mm. Inner pipes from the J, K and L models all had 29mm outlet holes. This is detailed on page 2 of the Suzuki Service Bulletin GT-7 which you can read at this link on my web site. This is only worth knowing if you happen to be mixing 1974 L inner pipes with later model inner pipes on a bike. 1974 inner pipes are not stamped “GT750” toward the rear of the pipe, whereas the 1975 and later pipes are all marked, however at a quick glance they do all look the same. That difference in baffle plate hole sizes may make carburettor set-up a bit of a challenge for the centre cylinder if you decide to mix and match. Just another thing to be aware of.

The project continues ! 🙂

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Piping Hot !

I need a set of exhaust pipes for the current project (see this link) and NOS or excellent condition ones are not easy to find for the 1972/1973 model Suzuki GT750’s. Mark Read did a very nice write-up on how to rebuild the original pipes, which he graciously allowed me to post on my web site at this link. However, I am not as skilled as he is, so I wanted to look at other options. Delkevic makes reproduction pipes for the later 1975 through 1977 models which will also fit the 1974 model year. I have discussed with Skid Brown of the UK Kettle Club about whether Delkevic were likely to come out with a set of reproduction pipes for the early models and that answer appears to be a ‘no’ at the moment. I actually have a spare set of brand new, still in the box Delkevic pipes, so I thought I’d look at how to modify them to suit the 1972.

I knew that the rear pipe hanger location of the early frames was in the wrong place for the later pipe hangers, but had assumed that dimensionally the later and early style pipes would be close enough that I’d be able to  perhaps just swap the end caps, fake some cross coupler pipes (or not – I’m not actually a fan of them), and fabricate a new rear hanger mount. You know what they say about assumptions. 🙂

The first step was to hang a spare new style pipe and an old style pipe on the project and check a few measurements. As expected, the new style pipe hanger was about an inch back from the J style frame hanger position (there is a photo somewhere nearby showing this). Not I problem I thought – I could make a new hanger bracket of some sort and that would work. That is when it got interesting.

Photo by Ross Thompson

The old style pipes have an end can that a black metal cone fits onto. These end cans are  held in place in the end of the pipe shell with a single spot weld on the inside of the pipe, and then the rest of the can is silver soldered in place. The silver solder can be removed by heating the end of the exhaust pipe, and using compressed air to (very carefully !) blow out the molten solder. However there is a small snag.

The new style pipes are both longer, and also not the same outside diameter at the ends as the old style exhaust pipes ! In fact, the new style pipes are about 3mm larger in diameter at the end (98mm vs 95mm). What this means is that if the end can is mounted into the newer style pipe, when the black cone is fitted it looks terrible, and as the black cones are such a key design element of the 1972 and 1973 model machines, I was not prepared to do without them.

There are other issues as well. The indents for the centre and side stand barely line up, plus there is the question about what to do with the cross couplers. The new style pipes are a different radius, sitting tighter to the front of the engine and frame, so there isn’t room to clear the frame at the front of the engine if dummy cross couplers are added. I could live without the cross couplers, but the alignment of the indents for the centre and side stands is more of a problem.

The bottom line for me was that while not impossible, it all just seemed like a lot of work and cost for something that would still not be as per the original. So I’ve given up on the idea of converting a new set of pipes to look like old ones for the moment, and have decided to have an old bashed up set of pipes repaired by ace metal worker Ross over in Ailsa Craig here in Ontario. That way, they will fit, and also look correct. I do not plan to have functional cross couplers: these will be plugged off as getting them to seal so they don’t drip oil all over the place is just such a pain. The slight loss in torque is not something I’m concerned about.

As I needed some spare internal baffles and also end caps as parts for the pipes Ross is working on, I took some time to cut open a few old pipes that were beyond salvaging just to see what the internal differences were.

When you compare the new style pipe in the centre of the nearby photo with a sectioned J/K pipe above and below it, the differences are pronounced. The late model pipe has much bigger, better designed more rigid internal baffle plates, and actually has one more plate than the J/K style. And I was surprised to see that at least this specific pipe was spot welded on the outside as well as on the backside on the last (closest to engine) baffle. You can see the location of the spot welds in the photo (just click on any of the photos to see a larger image). Another difference is that while both pipes have sound deadening mesh overlaying glass fibre wadding installed, the J/K pipe has more.  You can also see why it is they are so hard to get clean for re-chroming as that wadding holds a lot of oil. That wadding also will hold acid, and as Mark points out in his article on my web site, that will ultimately lead to accelerated corrosion rates unless the acid is carefully neutralised after re-chroming. And I’m not 100% sure if all the late model pipes have the extra outboard spot welds. I did a close examination of a few other late model pipes and while on some they are evident, that isn’t true for all. This is possibly just due to variances in the quality control on the finish, or perhaps they are added for the later A and B models. I do know that I’m not going to continue to cut pipes open to see ! 🙂

At any rate – sometime in the next three or four months I will have a ‘just like new’ set of pipes for the project. All I have to do now is get everything else ready so that the pipes become the ‘final’ touch !

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Totally Forked

I have been saving a new pair of Suzuki GT750 J/K style fork tubes (or stanchions if you prefer) for many years in anticipation of using them on a restoration, and the time finally had arrived. When I first looked at the old ones on the current project that I refer to as ‘Big Blue’ (see more on my web site at this link)  the chrome in the areas that the seal contact actually looked quite good and there was no pitting to speak of that I could see. This is obviously a credit to the rubber fork boots that had slightly survived all those years of sitting outside in all weathers. However, upon closer inspection, I discovered that one tube was slightly bent. While it could be straightened I decided to take advantage of the fact I had replacements and got to work. After all, replacing fork tubes is a simple job so how long could it take ? Quite a while as it turned out ….

I bought these tubes from CruzinImage in Japan via eBay, and while most of the time I’m really happy with both the quality and the value of their products, this was one of those instances where it didn’t quite hit the mark.  As a matter of interest, I note that CruzinImage hasn’t offered fork tubes for the J/K for quite some time which probably should have been a clue. There is a lower piston or valve that has to slide over the bottom of the tube (part number 51112-31030) and I found that the tube was just fractionally too big in diameter. As the tube is chromed, and as chromium plating is hard, my options were either to grind the surface of the tube down, or hone the inside diameter of the valve to make it bigger. My toy lathe has a very small through hole in the head stock, so I removed the tail stock and set the tube up using a steady rest with one end held in a chuck to see whether or not it would run true enough that I could use an oil stone to grind down the chromium plating. The reason for doing so is that replacement pistons/valves are hard to find, and so I didn’t really want to modify any good ones that I had. In the end, it worked well enough. And then I ran into another problem.

As the tube was ever so slightly too big, the circlip that the piston/valve butts up against prevented the valve from moving far enough up the tube to allow it to fully seat home. As a result, I found that the lower snap ring that secures the piston/valve would not seat into its groove. I seriously considered going back to the old tubes at this point, but then decided to go ahead and shave just a hair off the inside step of the piston/valve. Once this was done, it all fit together as intended.

My plan is to keep the old tubes and at some point I may look at trying to straighten them. In other places on the globe you can get tubes re-chromed and then ground back to the original size, but here in Canada there are not a lot of options. I do have the name of a place in Toronto, but the cost appears to be more than buying a new set from a place like Frank’s Fork (previously called Forking by Frank) in the USA or from Tarozzi in Italy. I have previously bought fork tubes from Frank’s and the fit was exact and the price was reasonable, so if I were to do this over again, that would be my first option.

And so the build continues !

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Updates and Additions

I have been lounging in a warmer place than Southern Ontario this past couple of weeks (in Southern California to be exact !).  In between carrying parcels as SWMBO’d shopped, acting as a tour guide to my daughter-in-law who was able to join us both here, and also entertaining my in-laws Judy and John, I have also managed to do a few updates and additions to the OJB web site. Some will already have seen the additional manuals that I added four weeks ago. Those included the addition of the :

And the:

As well, this week I have added the :

And the:

Just ‘click’ on the links above to take a look. I suspect that will pretty much complete the manual selection that I plan to offer. I’m still missing the T20 Parts and Owner manuals, as well as the T200 manuals but I’m good with that and if they fell into my lap, then I could eventually add them I suppose. My interest is really just road machines and so I hesitate to expand the offering to include models used off road, or indeed to road models offered outside of Canada. That could always change in the future I guess.

I still get requests from people to send them PDF’s of the material I have posted. As mentioned on my Manuals page I don’t do that. Excellent quality hard copy manuals are easy to buy at very reasonable rates from e-Classic Bike in New Zealand, or from Amazon and eBay etc. I know there are people who painstakingly copy down each of the images I post and then offer them around to people as PDF’s. They are low resolution images to make them load faster and often I’ve water marked them, but really if that’s what you want to do then have at it I suppose. Whatever turns your crank. And keep in mind that I have not designed these to be viewed on a phone. Having an old laptop or large tablet in the work shop is a cheap accessory, and it is what I’ve done for years. I encourage others to do the same.

In addition, I was also able to add a Japanese Domestic Market dealer manual that Drew Courtney in the UK lent me. This is quite interesting to page through as it shows models not offered elsewhere, along with dealer specific material such as retail prices in Yen for the different models. Having that material prompted me to update the section on the web site slightly and split the sale brochures area into JDM and ROW (for ‘rest of world’) sections which I can continue to add to as material comes available. You can view this new addition at this link.

Details of my latest restoration ( another 1972 GT750 ) are slowly starting to be added at this link on the web site . I expect it will be a slower build than others I’ve done in the past as it is taking me a while to track down suppliers offering the same quality of service in Ontario as I had access to in Calgary. I know they are out there – I just still need to do the due diligence and satisfy myself that I can get what I want at a price I’m prepared to pay.

And I also figured out the answer to a question about water pump seals that I’d been curious about. If you’ve wondered where to buy a replacement mechanical seal for your GT750 or for your RE5, then I wrote about that at this link , and now have also added the seal information to the web site here.

I’ve also added a small write up on making your own engine stand that Skid Brown in the UK has graciously allowed me to share here. This first appeared in the Kettle Club’s newsletter and you can read about it at this link .

Finally, I have started something completely different ! In response to a fellow who asked why I didn’t actually have much on the site about “really” old Japanese bikes, I have started to remedy that omission. I have started putting together a compendium of sorts which covers other JDM machines prior to roughly 1960. I very deliberately am not including much material on products from the ‘Big Four’ manufacturers as there is already loads of material available. For this project, I wanted to shine the light on the manufacturers that no longer remain. It is very much a ‘work in progress’ but you can take a look at what little I have done so far at this link.

That’s all for the moment. As always I continue to make other small changes and updates here and there – too many to list really. The errors and omissions are all mine and I very much do appreciate people letting me know if they find something that needs to be corrected.

The fun continues !

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Big Blue In Progress

Elsewhere in OJB land, I have been working on my next 1972 GT750 restoration. This one will be blue and like the previous red one I did a couple of years ago it is in really rough shape. However, it is the next consecutive frame number to the red one and I like the idea of former assembly line mates being returned to their former glory. Currently I have completely disassembled it, and the engine cases, block and head are away for vapour blasting at Wolf Worx Motorcycle here in London, Ontario. Before taking the block there I had Can-Am Machine remove one of the studs using spark erosion (EDM). Although I had been able to raise the block slightly, one stud had jammed/seized and try as I might, I could not get it to budge. I was able to remove the block from the cases after cutting the offending stud with a hacksaw blade and so rather than risk damaging the block, I decided to get some help. They did a really nice job.

I degreased the frame and checked to see if it was square using some string and a tape measure and generally it looked quite good, however the rear turn signal mounts were badly bent. After a few sessions with some heat and gently straightening the mounts, I was happy with the final result. For testing I am using a set of scrap signals with the long stalks just to check for true, but the ones I’ll be using on the final build will be quite a bit shorter. These welded stubs were only used by Suzuki for the early frames and then replaced by bolt on brackets in North America. Elsewhere in the world the signals threaded into shorter stubs right on the frame.

Next on the list is to tidy the frame up here and there before sending it out for powder coating. At this point, I’m still checking to see who I’ll use, but I’m sure I’ll be able to find someone local to the London Ontario area to do the work at a reasonable cost.

Internally the engine looks almost new ! There are almost no marks on the clutch basket fingers at all, and the gears in the transmission look pristine. There are some signs of spun bearings on the cases, but that is easy to fix with a bit of Loctite 638.

Externally though there are a few problems, one of which is that the block itself suffered a close encounter of the hard kind  on the left water jacket and has been repaired at some point. The repair weld was filled with Bondo and doesn’t look great, although I think I may be able to draw file the area to clean it up enough that it will look OK. If not, then I’ll have to consider my options. Of course, when you consider it is 47 years old I suppose a few battle scars are not something to be ashamed of.

The cylinder bores still show the cross hatch marks from the original hone and there is no sign of pitting so I think I may just buy some new rings, give the bores a quick hone and call it a day.

All in all – good progress !

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Kwakification and Drums

I know this will make my friend Wade happy, but the Kwakification of my Suzy’s continues ! I had always been curious where places like DiscountBikeSpares in the UK or GTReiner in Germany were sourcing the mechanical seals for the GT750 water pumps. Obviously someone was making them, and while these places provide excellent service I decided to do a bit of research. Terry at Wolf Worx here in London let me take a look through a couple of his supplier catalogues and one of them (MC Distributing) listed a whole page of after market mechanical water pump seals. With that information in hand and after asking the question on a couple of boards, it turned out that a suitable seal to fit the Suzuki GT750 seal is used in several Kawasaki’s, as well as some Chinese models. As with the oil injector valves (see my previous post at this link) the Kawasaki mechanical seal with part 49063-1055 is a direct fit and the cost is reasonable so I’m happy to buy them locally. As a matter of interest, it is also made by the same supplier (NSO) who made them originally for Suzuki.  Inglis Cycle here in London were able to get the Kawasaki part in for me at a cost of slightly under $26 CDN (taxes in). Note that the part comes with a new seal face (seen below the Kawasaki part on the left side in the photo above) that is not used on the Suzuki water pump, so you do still have to refresh the metal seal face that Suzuki uses (replace it, lap it or skim it on a lathe) in order to ensure a good seal. Note also that this mechanical seal also fits the RE5 water pump and was listed under Suzuki part number 17470-31010.

Via places like eBay, you can buy cheap Chinese knock-offs of this Kawasaki seal for as little as a $1 USD ! I bought a few different ones just to see how they compared with the Kawasaki one. The one in the photo to the right cost me about $14 USD, but on close examination does not look very well made. I think it would probably work OK, but not in one of my restorations, as I prefer to only repair them once if possible. As with the Kawasaki part, it comes with a seal face which you discard as well as an oil seal that is the wrong size for the Suzuki GT750.

DiscountBikeSpares in the UK sells the mechanical seal for about $47 CDN which seemed a bit high to me so I didn’t buy one from them. Reiner in Germany sells them for about $31 CDN (a bit more than that if you also live in the EU as VAT is added) which is close to the local cost here in Canada. The seals that Reiner sells appear to be repackaged Kawasaki parts, or at least are from the same OEM supplier as they are also made by NSO and are of very good quality. I’ve used the mechanical seals from Reiner previously and I’ve never had any issues. Both Reiner and DiscountBikeSpares use the Suzuki part number 17470-31010 if you go searching for them.

So when all is said an done, I find that I now have more than enough mechanical seals on hand; likely more than I’ll ever need I suppose. On the other hand it is nice to have another small mystery solved, which I hope will help anyone else who wishes to rebuild their own water pumps !

Changing gears a bit – there is a thread on the UK Kettle Clinic board (one of the better publicly accessible ones available if you want Suzuki GT two stroke assistance) about the differences between front drum brakes. Specifically front drum brakes as used on the 1972 GT750 and GT550 J models. The part numbers for both the GT750 and GT550 front drum brakes are the same, however there appears to have been two different versions of the front drum with earlier frame numbers below about 12400 on the GT750 having a narrower front drum assembly and so requiring spacers. Later frame numbers used a different part number for the drum assembly which was wider and so did not require the spacers. Purely out of curiosity I was wondering roughly when the change happened, and so I’ve put out requests to owners having low number frames on several boards and forums. If anyone reading this has a GT750 or GT550 with a frame number below about 12400 I’d like to hear from you as to whether you have spacers installed. To make it interesting (well – at least slightly more interesting I suppose…  🙂 ) I am running a small contest which you can read about on my OJB Facebook page at this link.

And so the fun continues !

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1972 Suzuki GT750 Gauge Shells – Update

After six long years, I am finally down to my last twenty sets of GT750J reproduction gauge shells and about fifty reproduction speedometer reset knobs. It has been a journey, but I have no regrets.

Recall that I started this project in 2012 when I picked up my first Suzuki 1972 J model and started taking a look at what options were available to repair the cracked plastic housings on the gauges. Suzuki only used these plastic shells for the 1971 Japanese Domestic Market and 1972 General Export model years, and they are often broken. Repairs are possible if the crack has not extended up into the clear plastic lens, but if the lens is also cracked then you have a real problem.  The idea of having the gauge shell reproduced came about following discussions with my friend Allan Tucker from Barbados. We looked at a few different reproduction options, none of which proved viable. I then started the process of reverse engineering the original design and had some duplicates created using 3D printing which at the time was useful as a ‘proof of concept’ but useless as a finished product. The issue was the clear plastic lens. The 3D printing materials and processes available at the time could not produce a clear plastic lens with the right optical characteristics suitable for a restoration. I suspect the same is still true today. While the test blanks were of no use as replacements, they did confirm the design and provided me with a sample that I could then show to injection moulding companies.

In the end, I went ahead by myself to finance and organise the manufacture of the shells, and as I first documented (at this link) a company in Edmonton worked with me to create what I think is an excellent product.

When I first looked at having these shells reproduced I tried to guess how large a market there was. The original GT750 production numbers would indicate that about 20,000 of this model were originally sold worldwide. Hagerty Insurance in the US published an interesting chart giving survival rates of motorcycles by manufacturer which showed that about 45% of all Suzuki’s were still in use after 25 years. Extrapolate this out to 46 years and the number of survivors starts to look quite small – certainly less than 10%, so for 1972 model year GT750’s specifically perhaps as many as 2000 machines. While the numbers for a specific model like the GT750 will differ from a those of a Suzuki moped, I note that the sole GT750 registry I know of, which is maintained by Martin K. in Germany, only shows about 420 GT750 J’s in total. If you then consider that not every gauge shell is cracked, and that some people are happy to use later model gauges rather than the originals, then it becomes clear that the total available market for this product is quite small indeed. I do still own the injection dies, and now that the cost of creating the dies has finally been recovered, a second production run of tachometer and speedometer shells would be much less costly to produce. At the moment though, I am not planning on having more of these shells made as I suspect the available market is near saturation. At the rate of current sales, what stock I have left should last about one more year (so mid to end of 2019) and then perhaps I will re-evaluate my decision.

And of course there is still the problem of the temperature gauge shell as I only had the tachometer and speedometer shells copied. I didn’t do it initially as the temperature gauges are often not damaged, and as well due to the manufacturing costs of the injection die they would have to sell for about the same cost as the larger tachometer and speedometer shells do currently. Cost is definitely an issue for some owners, but it would be a nice addition for restorers. Possibly a future project for someone else perhaps !

For the three 1972 GT750’s of my own, I now have fully refurbished gauge sets so the original problem that started me down this road six years ago has been addressed. And roughly 180 other GT750 J owners’ world wide have also benefited, so I’d call that a success !


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Just Tooling Around

I like to have a complete, as per original, tool kit for my restored bikes. While it is possibly true that the original factory tools were not the best quality or the most useful, in my view no restoration is complete without this final touch. While many of the Suzuki factory original tools are fairly easy to find, for the GT750 specifically there are a few specific tools which are increasingly hard to source. Examples would include the contact points tool (09930-20111), the open end 8 mm wrench (09813-00025) which also served as the T handle for the cross head driver and finally the small  10mm box wrench, or spanner which is part number 09816-00001. A photo of the original tools is near here – just ‘click’ to see a larger version. The 10mm box wrench was included in tool kits fitted to the 1972 through 1974 GT750’s plus earlier bikes like the B100P etc., and necessity being the mother of invention, I decided to make a few.

I have two uncles who know a thing or two about making things out of metal, so after getting a few suggestions from Don specifically, I sourced some seamless tube in various wall thickness’s from a company called Aircraft Spruce Canada and did some experimenting. You need to use seamless tubing for this process, as welded tube will split when you try to form the tubing over your mandrel. 

The photo to the right taken by a friend of mine in Calgary by the name of Art, shows what an https://oldjapanesebikes.comoriginal 09816-00001 tool looks like and its approximate size. It measures roughly 1 3/4 inches long and is about 1/2 inch in diameter. What I wasn’t sure of was the wall thickness so to cover my bases, I ordered a couple of different wall thickness’s and also two different OD measure tubes so I had a selection to try. I had never tried doing this before, and so after several attempts using different methods (heated or cold) and also trying the various different sizes of tubing I had to work with, I had a nice selection of scrap as can be seen in the second photo.

The successful solution was to slowly press a thicker walled tube over the mandrel I’d made with the tubing cold but generously lubed with a cutting oil. Some time ago a friend in Calgary (John) gave me a 20 ton press that he no longer needed which makes this quite easy. To finish it off took only a few minutes on the drill press and then a bit of time to dress the edges.

The finished product can be seen to the right below and I am quite pleased with the result. I now just need to get them zinc plated along with the rest of the tools and Ill be good to go !

On to the next challenge !

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