1982 GS750T: Warped Front Disc - Replacement Question...

[SamLack99]

01-front-brake-mot.jpg

Took Suzy for an MOT today (she's exempt, but I want to make sure she's safe after me wrenching on her for two years).

She failed on two points:

1. Headlamp not working on dipped beam (I'll see if a new bulb fixes that).

2. Brake grabbing severely front.

Fault two didn't come as a surprise. After fitting a new master cylinder, braided hose and brake caliper kit... I could feel the brake lever pulsing slightly when I pulled it.

My question...

Are there other motorcycles in Suzuki's '80s lineup that used a similar front disc?

The OEM part number is: 5922134550, and one is available at CMSNL for £245 + shipping.

I'd prefer to get something in the UK (to avoid shipping costs) and possibly avoid paying £245 for a replacement front disc that isn't warped <-- It doesn't have to be new.

Any advice from you, awesome GS owners, is very much appreciated.

[Nessism]

Nice looking bike!



According to Partzilla, these are some other bikes that used that same disc PN
SUZUKI 1981 GS550T FRONT WHEEL

suzuki gs550t — 1981 SUZUKI 1981 GS650GL FRONT WHEEL MODEL X

suzuki gs650gl — 1981 SUZUKI 1981 GS650GL FRONT WHEEL MODEL Z

suzuki gs650gl — 1981 SUZUKI 1982 GS650GL FRONT WHEEL MODEL X

suzuki gs650gl — 1982 SUZUKI 1982 GS650GL FRONT WHEEL MODEL Z

suzuki gs650gl — 1982 SUZUKI 1982 GS750T FRONT WHEEL MODEL D

suzuki gs750t — 1982 SUZUKI 1982 GS750T FRONT WHEEL MODEL Z

suzuki gs750t — 1982 SUZUKI 1983 GS650GL FRONT WHEEL

suzuki gs650gl — 1983 SUZUKI 1983 GS750T FRONT WHEEL MODEL D

suzuki gs750t — 1983 SUZUKI 1983 GS750T FRONT WHEEL MODEL Z

suzuki gs750t — 1983

[dgates1]

Looks like it's used on 12 different models. See at the bottom of this page.

https://www.adeptpowersports.com/oem-parts/suzuki-disk-front-brake-59221-34550-part.html

[Nessism]

You may want to measure thickness, and if above standard, get it ground flat.

[first timer]

EBC flys the Union Jack, I would see about getting a new rotor from them.

https://www.ebcbrakes.com/motorbike/uk-row/SUZUKI/GS%20650/

You have vintage style and standard style.

https://ebcbrakesdirect.com/vintage-design-brake-disc-vmd3014

[Rob S.]

Now that's a proper motorcycle! Aside from mirrors, no unnecessary crap bolted on.
Owner: I agree with you. Less IS more.

If you absolutely must add accessories, feel free to choose from the following list:

Oil cooler
Steering dampener
Fork brace
Radar detector

[Nessism]

This one is expensive, but looks to be worth the cost.

https://www.ebay.com/itm/235311101377

[rphillips]

Local machine shops have been handy for me, truing bike brake rotors... Seems reasonable to ask one, or some, if they could help... Very nice looking bike. Good luck.

[SamLack99]

You guys really are the greatest.

Thank you.

Plenty to work with here and you've helped me to move forwards.

This is my current plan of attack:

1. I saw this at a breakers in the UK. I've contacted them to see if they can guarantee it isn't worn. At £32+postage - It could be a bargain

2. The one Nessim recommended looks perfect. At £147+shipping+import duty - It's expensive, but not as expensive as option 3

3. This one from CMSNL. If all else fails I'll bite the bullet and pay £243+shipping+import duty.

I'll keep you posted how it all works out.

Thanks again for the advice, much appreciated gentlemen =)

[SamLack99]

Help!

The part I ordered from the breakers was guaranteed to fit the bike and not be warped.

I went to swap it today for the original.

Here's the picture...


02-gs750t-1982-front-disc.jpg


...See if you can spot my problem?


That's right.

The one taken off the bike (top) is about 270mm in diameter.

The replacement is about 295 in diameter.

Now then, looking at the parts diagram for the 1982 GS750T (here) you see the disc looks like the bottom one. The pattern from the centre of the disc to the disc on the top one is very different. Leading me to think, it's not original.

I'm pretty confident the replacement disc is original.

My question (other than why?) is this:

Will the 295mm diameter disc fit into the brake caliper?

My beginner bike-wrenching brain tells me that extra 25mm could cause serious issues with the current setup?

Or am I wrong?

Help!

I'm stuck (again) as to how best to proceed with this bike.

Your thoughts and experience on this topic are greatly appreciated =)

[Rich82GS750TZ]

I have a 750T. I’ll measure tonight.

[SamLack99]

I have a 750T. I’ll measure tonight.

Thanks Rich, much appreciated

[SamLack99]

UGH!

New development.

Whilst waiting for advice from the wonderful chaps on this forum, I thought: "I know what, I'll fit Suzy's new OEM brake pads."

Should have known.

Take a look at the photo below:

03-brake-pads.jpg

The pads I got are the genuine part number for a 1982 GS750T.

But I couldn't get them to fit in the caliper assembly.

Comparing them to the pads that came out...

...I can see why.

It's like I keep buying the correct parts for a GS750T... But they're replacing non-GS750T parts.

And that has a knock-on effect on the other parts in the system.

Fortunately, it seems the GS450L 81-83 front brake caliper is the same as the GS750T... And they are plentiful from the breakers here in the UK.

For example: HERE

So...

...I'm hoping that if I get the correct Brake Caliper, it will solve my problem with the bigger disc.

What do you think?

[Grimly]

The caliper mounting bracket will likely be different anyway.
So, somebody fitted a complete front end off another model onto yours, by the look of things.
Given that you now have 35mm fork tubes, iirc, it's likely it was a 450 or 550.

[salty_monk]

As far as I know only the 450 had that front end with the 274mm disk. It's good for spares though as any of the post 1980 dual brake models use that disk.

You can also fit the twinpot mod single sided to that fork, it's been done before (even using that 295mm disk you just bought but it's not ideal as it doesn't run central in the caliper, CBR with the spacer is better).

Check the back of your disk is FLAT on the mounting side & that there is no crap in the bolt holes or dents on the hub. A lot of pulsing is caused by the mounting surfaces not being completely flat on the GS in my experience.
It maybe started after your last brake work because you took the disk off, dislodged some RUST (with it being the UK, there must be rust ) and that's your problem.

If you need a kit to move to Twinpot instead then let me know.

Dan