Ignition – GT750 Project

There are several electronic ignition options available for the GT750 and include the Boyer Bransden, Newtronic , and roll your own as described on the Pink Possum web site.  

 

If you search the web, the kit that seems to have the best reviews is the Newtronics kit as it is packaged as a Suzuki specific item – for example you supposedly do not need to butcher your wiring to install it.  See Gunner’s write up on the Newtronic unit here. However, as of this writing Newtronic are no longer in business, although their SU6 kit can still be found if you look, and the new owner - Autocar - may start selling them again. Given availability issues, I went with the Boyer Bransden unit which I bought from Walridge Motors who are the Boyer distributors here in Canada. Walridge Motors is actually a vintage British motorcycle supplier, and they were very easy to do business with, and quite helpful. They also stock the old style metal core ignition wire which is handy for repairing old Suzuki ignition coils if you have the need. 

I won’t repeat what Gunner has mentioned about the Boyer Bransden model KIT00083 kit to fit the Suzuki triples, other than to agree that it is a bit disappointing as it is actually a made over kit intended for a Kawasaki and as such it lacks the correct mounting plate, the correct wiring diagram information or even what I’d call ‘good’ set-up information. Having said that, it wasn’t too hard to figure out and install. I did have to modify the Suzuki mounting plate as the rotor supplied in the Boyer kit was too big for the hole in the centre of the points mounting plate as seen to the left – I opened the hole up with a step drill bit. I also made a rubber pad from an old inner tube to fit under the Boyer contact plate which was probably not really required, but seemed like a good idea as the Boyer supplied plate is not very rigid.  The mounted point plate can be seen in the photo below.

On the plus side – once I had it installed, the bike did start up with no trouble at all so my first impressions are positive. The folks here in Calgary that I’ve spoken to who have the Boyer Bransden unit installed, all seem happy with the product, and several of them have had years of use with no problems at all, so we will see how it goes.

It should be mentioned, that a decent dial gauge is a must for doing the initial setting of the timing, and a good list of available options is offered on Gunner’s site. I actually built my own dial gauge using a cheap unit fromPrincess Auto (part 2970986) which was on sale, and an old NGK spark plug which I modified to be a holder. It has worked well for me for years at a total cost of less than $10 CDN and is shown below.

Carburettor Rebuild – GT750

With the engine in the frame, and the electronic ignition fitted in my GT750 project bike , it was time to dig into my box of bits to see what I could do in the carburettor department.

The local Water Buffalo folks have been urging me to use the Amal style VM 32 carbs as used on the early GT’s, as these do provide better throttle response and also flow better than the Mikuni constant velocity (CV) BS40 carbs used on later models. In the interests of simplicity, I plan to start with the later style CV carbs and then look at replacement options later as they are (I think) easier to set up and will require minimum modification to my current configuration. If I use the VM carbs, then I would have to find a three-into-one throttle cable, as well as the handle bar mounted choke lever and its cable assembly, fiddle with the air inlet boots on the  engine as they are a different size,  modify the air outlet from the air box as that is also different (or switch over to carb mounted air filters) and switch to a cable actuated oil injector setup rather than use the CV style pull rod.

Frankly – I just don’t have the energy to start making this number of changes at the moment, and since I have access to additional CV units via the local CVMG club to supplement the box of parts I’m starting with if required, then CV it will have to be. One change I will be making is to rejet the main jet on the centre carb to match the two outside ones as I will be using a three into three exhaust pipe setup, rather than the stock setup in which the centre cylinder exhaust was split into two pipes.  For a main jet, I’m starting with a 115 rather than the stock 110 and we’ll see how that works. The other thing I’d like to do, but will probably pass on for the moment is to install the ‘anti-surge’ fix that was detailed in Service Bulletin GT-36, March 11, 1977 and which can be found here. As I will not be using a stock exhaust system I thought I’d wait and see whether it will actually be required. 

I used the Keyster KS-0029 kits to rebuild the carbs – everything they supplied fit just fine, but I was slightly disappointed that the small o-ring (part number 13295-31210) for the needle jet was not included, nor was the fuel filter (13376-65010). Both of these are still available from Suzuki, but it would be nice of Keyster to add them to the rebuild kit just to make it fully complete. These kits are available all over the place and can be picked up on eBay for between $15 USD to $30 plus shipping.  Luckily the kits do include new starter plungers which are not available from Suzuki, as these were all noticeably worn at the shoulder  where the actuator engages it. The photo to the left is slightly out of focus, but gives the general idea.

 The other problem I had (other than the usual corrosion and cleaning items) was that the oil pump arm was missing the small plastic ball used to connect the carbs to the oil injector pump rod.  Each of the available carbs I had all showed the same problem as the metal bush the ball mounted into was so badly worn that it wouldn’t stay. Fortunately, Fred in the local CVMG had a spare carburettor set I could use for parts, and so I swapped out the shaft as can be seen in the photo to the the right. My younger son Derek handled the metal polishing of the carbuerettor caps, and he did a nice job of making them look almost new again ! 

So – now I finally have a set of carburettors ready to go so the next step will be to see if I can get the engine started !

GT750 Rebuild – Instruments

For my GT750 project bike, I was faced with the option of either rebuilding or replacing the gauge set as I was starting with just a box of bits as seen to the right. I have been collecting these for many years, and had been using them as a source of parts for my other two GT750 bikes – as a result, what I had was quite a jumble. Fred, the Calgary GT guru was kind enough to let me poke through his own bin of gauge parts and pieces so between the two I was able to rebuild something that works.

There are several ways to rebuild these – the best write-up I’ve seen is by Paul Franchina who wrote an article published in 2004 for the VJMC member magazine and which also appeared in 2005 on what is now a dead speedometer repair web site. If you are a VJMC member, then you can find the VJMC version in the 2004 member archives, otherwise you can download a copy of the 2005 public web article from here. Getting the chrome ring off and then re-installed is the hardest part, and rather than prising it off as Paul describes, a second method some folks use and which can be simpler to do is to use a small cut-off wheel (on a Dremel for example) and just cut the ring, rather than trying to prise it off as described in Paul’s article. To reinstall the cut ring, the suggested method is to use a similar clamp/jig setup as Paul uses, but then use epoxy glue to fasten the ring which is held in place and positioned using gear clamps. If done well, the cut is not easily visible, and as the ring is not deformed in any way, the ‘fit and finish’ is a bit cleaner. Of course should you ever have to take the gauge apart again, you will have a bit of a problem because of the glue, but it can work quite well. The best option of course would be to replace the ring with a new one, but a special tool would be required to reset a new ring on the gauge housing. I have been talking to Wolfgang Haerter  who does this using a lathe and tool he made for this purpose when restoring Laverda gauges, but it isn’t an option for most shade tree mechanics.  The ring size he uses appears to be about the same size as is used on the Suzuki gauges so I will likely have him give this a try in 2009, but of course he doesn’t have anything to fit the water temperature gauge, so I’ll have to sort that out myself.

Gauge sets are available fairly often on eBay, but generally suffer as they are obviously 30 to 36 years old, may have been sitting outside in the weather etc. and the speedometer usually is missing the trip meter reset knob as this is easily broken off or lost. Generally these will start at about $50 USD for a single gauge through to whatever level people get carried away with during the bidding. NOS and professionally rebuilt GT750 gauges are available from GTReimer in Germany, and sometimes from folks like Paul Miller in the US.  These new or professionally rebuilt gauges will range in cost between about $200 USD to $400 USD depending on exactly what you are looking for – the plastic housed gauges on the early models usually cost more than the metal housed gauge sets used from late 1974 onwards.

Here is where I got to – you will note that the water temperature gauge is brown. The brown faced gauges appeared on the GT750 in late 1976 through 1977 and so in keeping with my theme, would likely have been used also in 1978 had a GT750 continued to be made. I have a brown faced tachometer which I will be rebuilding at some point in 2009, and am keeping my eye’s open for a brown faced speedometer, but for the moment will make do with the most common blue-green coloured ones as I had enough parts to put one set together.

The Coyotes Aren’t Singing !

It appears that winter may finally have truly arrived here in Calgary, as the current temperature according to the thermometer by the back door is about -25 C,  and the local news channel cheerfully reports that with the slight breeze that is blowing, it actually feels like -34 C. For my Australian cousins in Perth, that would be roughly 55 degrees Celsius colder than your current temperature as measured at 2 am your local time today – it is just a tad on the frosty side in other words. As well we have also had yet another fresh dump of snow as can be seen in the photo to the right.

All of this snow is starting to pose a bit of a problem as it is only mid-December, and as I clear the driveway and walkways, I am already running out of places to put it ! As may be expected with something that is delivered to your home free of charge and in large quantities, snow has no resale value in Calgary at all. Last year, as our former neighbours Gwen and Brendan relaxed on a beach for the winter somewhere in sunny Mexico,  only half of their driveway was being cleared so I saw no harm in adding some of my snow to the un-dug heaps that they were collecting on their side of the property line, assuaging my conscience by knowing that it would largely be melted by the time they returned and none would be the wiser ! This year though, we have new neighbours possessed of enviable snow shovelling habits, so storing snow surplus to my own requirements on that side is no longer an option.  Perhaps I may end up loading it into my trailer and hauling the excess snow to the dump to join my compost already deposited there.

At this time of year, the coyotes can usually be heard singing away at night in Fish Creek Park behind our place, but they were not singing last night ! Possibly given a choice between partying and keeping warm, they have done the sensible thing – unlike the dog owners who can be seen today trudging along  in the park with a leash in one hand and their very quickly frozen collections of animal emissions stored in a plastic baggie clutched tightly in the other ! As I watch them, neither the owners nor the dogs look especially pleased about their enforced morning constitutional strolls in the frozen fields, and it occurs to me that perhaps that is why the coyotes sing – they aren’t on leashes and they are not bound by city stoop and scoop laws, but I digress.  It is quite pleasant and warm here beside the fireplace as I consider whether I should head outside and shovel snow yet again and also where to put the stuff.  I suppose I may convince myself that there really isn’t any hurry and just go and do some more work on my motorbike, as we have several months of winter ahead of us, and I’m reasonably sure the snow will still be there tomorrow. Plus, it just occured to me that there is always the possibility that our new neighbours may also go somewhere warm for the winter, so I may be able to store some of my surplus frozen white stuff on their yard while they are gone …………….