Newbie

[stevesjclark]

Hello all from West Yorks. After being on here for a few months gleaning advice for buying a kettle, I let my heart rule my head and bought a 1974 GT750 from 'down south' after seeing photos, the bike having been restored 2017. On first ride found seemed to go ok but little retardation on braking and change of underwear required. Calipers overhauled as pads found seized in brackets, now slightly better. Trying now to sort carbs as tick over seems erratic. Having had many bikes in my 47 years of motorcycling, and wanted a GT750 since 1976 i finally have one!!!

[mick 63]

Hello and welcome , i to have a 74 GT750 mines in Blue , and there are a few others on here , there is plenty of knowledge on here if needed , post some photos of your bike when you can , cheers .

[Alan H]

Welcome Steve. Plenty of help for another Yorkie, although I've recently upgraded from the Hippo 'B' model, and now have 3 x GT550s!

[750ynot]

Hi, Nice when you get something you wanted all that time ain't it.

The breaks are a bit wooden to say the least, a great way round this is to fit a 12mm front master cylinder, I have a Honda VFR750 one on my bike, works a treat, wouldn't go back to standard now.

Carbs most likely want a clean, choke plungers can be an issue, the rubber tip gets damaged over time, though someone may have fitted an aftermarket kit, only way to find out is to strip and clean carbs thoroughly, all the passages need to be clear.


This will help http://pinkpossum.com/GT750/carb/BS40carbs.htm

[Alan H]

Make sure that the master cylinder has a 'D' stamped underneath (for 'dual discs) but I believe that the piston is 14mm - 12mm is for single disc. Another alternative is to use a GS1000 setup, including calipers which carry bigger pads. A Suzuki Bandit 1200 master cylinder is another improvement, but the reservoir is a different shape, so doesn't look 'standard'.
Rebuild info here - https://www.oldjapanesebikes.com/mraxl_ ... der_Re.pdf . There's also caliper rebuild info on that site.
Another option is this - viewtopic.php?p=106028&hilit=sv650#p106028 - and it upsets the purists too!
I fitted GS cast alloy wheels to one of my 550s with twin discs (and another disc on the back) which works well and a Bandit lookalike master cylinder to match the one on the left 'bar for the hydraulic clutch. 6th post down here - viewtopic.php?t=5620&hilit=clutch&start=310 .

[750ynot]

Make sure that the master cylinder has a 'D' stamped underneath (for 'dual discs) but I believe that the piston is 14mm - 12mm is for single disc. Another alternative is to use a GS1000 setup, including calipers which carry bigger pads. A Suzuki Bandit 1200 master cylinder is another improvement, but the reservoir is a different shape, so doesn't look 'standard'.
Rebuild info here - https://www.oldjapanesebikes.com/mraxl_ ... der_Re.pdf . There's also caliper rebuild info on that site.
Another option is this - viewtopic.php?p=106028&hilit=sv650#p106028 - and it upsets the purists too!
I fitted GS cast alloy wheels to one of my 550s with twin discs (and another disc on the back) which works well and a Bandit lookalike master cylinder to match the one on the left 'bar for the hydraulic clutch. 6th post down here - viewtopic.php?t=5620&hilit=clutch&start=310 .

Aren't they 5/8 for the Bandit, 15.9mm, that will make the brake even harder to operate.


14mm is for twin disc and a 12mm one is technically for a single disc you say, I have a VFR750 master cylinder on my bike, a VFR750 is a twin disc bike, it uses a 12mm master cylinder, but the fact is that a 12mm master cylinder will make the brake action easier, it does feel a little spongy, but the bike stops a lot better than a standard 14mm one will.

[Alan H]

It all depends on the calipers. If you have (say) 6 pot calipers, then you need a bigger master cylinder to move them. The standard Suzuki calioers are only single piston on the GTs, but you have two single pot calipers so need a slightly bigger m/c than for a single unit.

[750ynot]

It all depends on the calipers. If you have (say) 6 pot calipers, then you need a bigger master cylinder to move them. The standard Suzuki calioers are only single piston on the GTs, but you have two single pot calipers so need a slightly bigger m/c than for a single unit.

Its the same on RD250LC and 350LC, the 250 has 1/2 inch just over 12mm for a single caliper, the 350LC has a 5/8 inch 15.9mm master cylinder and 2 discs, all calipers are single piston, the brakes are terrible like the GT, it is advised that you use the 250lc master cylinder on the 350LC to improve breaking, the standard master cylinders were fine in their day, but today most other road users have ABS ect, the old 5/8 master cylinder would be like trying to use 2 pieces of wood to stop the 1/4 ton of bike, the later 14mm was better, but if you want a brake that will stop the bike in a hurry, my advice is to fit 12mm master cylinder.

I am presuming the op has standard calipers and not 6 pots or 4 pots or twin pots, just single pot on both calipers.

If you have a grip like a vice, then there shouldn't be an issue, but if you are an aging human, the 12mm master cylinder is the way to go.

Now you get more travel of the lever, you could if you wanted pull it all the way to the handlebar grip, but then you fly over the handlebars, this mod gives you much better feel of the brakes and allows you to put more pressure on the pistons than a bigger bore master cylinder does with the same pressure applied at the lever.


I hear what your saying Alan, but the fact is, a smaller bore master cylinder will move the pistons easier, making braking easier at the lever, that is a fact.

Alan, if you haven't tried this, don't dismiss it out of hand, try it 1st and you will see what I mean for yourself, I am talking from my own experience, not something pulled off tinternet, I have tried and tested, and it works much better with 12mm.

Just trying to offer a solution to the problem that works, the bigger the bore of the master cylinder the more pressure needed to move the brake piston, the smaller the less force needed, that is just the way hydraulics work.

[stevesjclark]

Thx for your replies. Had a look under the master cylinder and there is a ‘D’ stamp on it, so assume that is correct for the twin disc setup. Wondered if fitting the ebc discs would improve the feel / stopping power, any experience of these?

[BAZ]

Welcome Steve.