77 GS750B Front Caliber - What make/model will swap?

[93Bandit]

Is anyone aware of an affordable rebuild kit for a 77 that contains ALL the dust boots and the seal? I've found a few kits online that claim to fit, but they're missing some of the dust boots. I can order the parts individually on Parts Outlaw, but just for the piston seal, 4 o rings and 4 dust boots (still missing the piston dust boot because it's unavailable) it would be $75. And I also need new pads and that piston boot which are dang near impossible to find. One ebay seller has pads and he wants $50. So I'd have nearly $150 into this caliber just in rubber parts and pads, and still be missing the piston boot seal. All the rubber on my caliber is cracked or shrunk so reusing is not an option.

Is anyone aware of a caliber off a newer GS, or different model GS that will bolt up and work that is more affordable to rebuild and find parts for? FYI, this is a single front caliber if that matters.

If anyone has a caliber they'd be willing to part with that would fit, I'd be happy to pay! (It'd be nice if it wasn't stuck too! )

Appreciate the help!

 

[allojohn]

Salty_Monk sells upgrade brackets - he's most likely to know what your options are.

 

[salty_monk]

Does the 750B have an axle under the fork leg like your G or in front of it like the L? What size rotor is on it now? Is it a 274mm like the G or larger one (296mm)?

 

[93Bandit]

Does the 750B have an axle under the fork leg like your G or in front of it like the L? What size rotor is on it now? Is it a 274mm like the G or larger one (296mm)?

Thanks for chiming in.

Axle is under the fork leg like the G. Measuring the best I can with it on the bike, I measured 11.5" so that should be the 296mm. Center to center the mounting holes on the fork leg are ~71.5mm, slightly closer together than on my L. Not sure what the G measurement is. Picture below.

20220104_174638

Ideally I'm looking for the most "factory" replacement as possible, as in reusing current rotor, master cylinder and ideally being affordable to reseal if buying used and available pads that won't cost an arm and a leg.

 

[salty_monk]

Your path of least resistance is to follow this setup using the blackbird rotor : https://www.thegsresources.com/_for...e-Upgrade-on-GS550E-GS750C-GS1000C&highlight=

Looks like it's the same as the 550E or the 1000C if the rotor is that size. Have a double check as that looks like one of the smaller rotors (by the spider) as the larger ones are usually 1 piece. The difference in diameter is only 3/4" so not always easy to see when mounted. (approx 10 3/4" vs 11 5/8")

The latest bracket accomodates the Ninja caliper or the more modern EX650 caliper (also the SV650 or DL650 caliper as they are the same). You can re-use the master & the lines (although I would be fitting new braided one if you haven't already).

 

[93Bandit]

Thanks for the information. Your blackbird rotor method is quite a bit more expensive than rebuilding my caliber considering I'd have to purchase the rare rotor and a caliber... Or are you suggesting it's possible to use my rotor with that same setup?

I will pull the wheel off tomorrow and double check the rotor size.

 

[Nessism]

Dan's method is ideal if braking performance is important. If the end game is simply to improve your braking system, in many cases a later year GS/Tokico caliper will be a bolt on. Rebuild that, install a new braded stainless/teflon hose w/new pads, and the worlds your oyster.

 

[93Bandit]

Dan's method is ideal if braking performance is important. If the end game is simply to improve your braking system, in many cases a later year GS/Tokico caliper will be a bolt on. Rebuild that, install a new braded stainless/teflon hose w/new pads, and the worlds your oyster.

My end goal is a fun bike to ride around town. It will see zero track time and I don't ride hard at all. So factory performance is sufficient.

@Burque73 is selling front calipers off a 1982 GS650G. Can't tell from the parts list image if they will fit or not. Does anyone know if they will?

As for brake lines, I will be using Earls parts and building new ones.

 

[salty_monk]

The G caliper should fit your bike, you may have to change to the 550E/1000C rotor worst case. I believe all the calipers will interchange except for L models.

 

[Grimly]

My end goal is a fun bike to ride around town. It will see zero track time and I don't ride hard at all. So factory performance is sufficient.

Believe me, the early hockey-puck calipers are utter rubbish compared to even the ones that came immediately after. That was my experience with two of them on the 79 850, and I was glad to discover the later calipers fitted straight on as a factory upgrade, if you like. Even the later ones aren't perfect, and they're out-performed by much more recent calipers and discs, as Dan suggests. However, as a cheap and effective upgrade, if you can get a low-mileage caliper from an 80-onwards bike, you'd notice the improvement.

 

[93Bandit]

Believe me, the early hockey-puck calipers are utter rubbish compared to even the ones that came immediately after. That was my experience with two of them on the 79 850, and I was glad to discover the later calipers fitted straight on as a factory upgrade, if you like. Even the later ones aren't perfect, and they're out-performed by much more recent calipers and discs, as Dan suggests. However, as a cheap and effective upgrade, if you can get a low-mileage caliper from an 80-onwards bike, you'd notice the improvement.

Thanks for the input. So the 82 GS650G should fit and be an upgrade in braking?

 

[Grimly]

Thanks for the input. So the 82 GS650G should fit and be an upgrade in braking?

If the mount is the same and the diam / offset of the disc is the same, I think it will fit.

 

[Burque73]

My end goal is a fun bike to ride around town. It will see zero track time and I don't ride hard at all. So factory performance is sufficient.

@Burque73 is selling front calipers off a 1982 GS650G. Can't tell from the parts list image if they will fit or not. Does anyone know if they will?

As for brake lines, I will be using Earls parts and building new ones.

I didn't list it, but I also have the front wheel with both rotors from that 650G. My thought was to hang onto an extra set of rotors to eventually swap them over onto the 850. Honestly, I'd much rather them help someone get back on the road than sit in a "maybe use eventually" pile here.

Let me know if I can help.

 

[93Bandit]

The G caliper should fit your bike, you may have to change to the 550E/1000C rotor worst case. I believe all the calipers will interchange except for L models.

Pulled the wheel off and double checked rotor diameter. It's the 296mm.

If the mount is the same and the diam / offset of the disc is the same, I think it will fit.

Unsure about those measurements and I don't know if I can get them.

I didn't list it, but I also have the front wheel with both rotors from that 650G. My thought was to hang onto an extra set of rotors to eventually swap them over onto the 850. Honestly, I'd much rather them help someone get back on the road than sit in a "maybe use eventually" pile here.

Let me know if I can help.

Thanks for chiming in Burque. I'm interested in at least one front caliber if it will fit my 750. Could you measure center to center of the mount holes on the fork leg to compare to mine? If that dimension is the same, maybe we can work something out. Also, are the caliper pistons free or are the stuck in need of rebuilding?

On a side note, I was really hoping to have this bike road ready come spring, but it seems like every where I turn there's something else that needs to be fixed. Joys of working on older machines! My wife and I are expecting our 2nd child end of April, so after that I won't have any garage time for a while so I really want to get this thing going before that, budget permitting. Fingers crossed!

As always, all the help from everyone is greatly appreciated!

 

[Burque73]

Pulled the wheel off and double checked rotor diameter. It's the 296mm.



Unsure about those measurements and I don't know if I can get them.



Thanks for chiming in Burque. I'm interested in at least one front caliber if it will fit my 750. Could you measure center to center of the mount holes on the fork leg to compare to mine? If that dimension is the same, maybe we can work something out. Also, are the caliper pistons free or are the stuck in need of rebuilding?

On a side note, I was really hoping to have this bike road ready come spring, but it seems like every where I turn there's something else that needs to be fixed. Joys of working on older machines! My wife and I are expecting our 2nd child end of April, so after that I won't have any garage time for a while so I really want to get this thing going before that, budget permitting. Fingers crossed!

As always, all the help from everyone is greatly appreciated!

The mounting holes are 72.43mm or 2-27/32" center to center, give or take a hair.

Since the calipers are already off of the forks I struggled to get the bolts (axles?) out to separate it and check the piston. It got late and it's cold in the garage too. I may try a bit of compressed air to move the piston tomorrow. The climate here and in Colorado where this bike lived is pretty dry, plus all of the fluids I drained from this 650 were the appropriate colors so the PO took care of maintenance it seems.

What if you took both calipers, the fork legs, rotors and scrounged up a spoke wheel that you could put another rotor on. That'd be a sweet upgrade. Sounds too easy though. The upper fork tubes are 35mm. Would they even fit a 750? These are 31-3/16 long from the top to center of the axle.

 

[93Bandit]

The mounting holes are 72.43mm or 2-27/32" center to center, give or take a hair.

Since the calipers are already off of the forks I struggled to get the bolts (axles?) out to separate it and check the piston. It got late and it's cold in the garage too. I may try a bit of compressed air to move the piston tomorrow. The climate here and in Colorado where this bike lived is pretty dry, plus all of the fluids I drained from this 650 were the appropriate colors so the PO took care of maintenance it seems.

What if you took both calipers, the fork legs, rotors and scrounged up a spoke wheel that you could put another rotor on. That'd be a sweet upgrade. Sounds too easy though. The upper fork tubes are 35mm. Would they even fit a 750? These are 31-3/16 long from the top to center of the axle.

I set my dial caliper to 72.4 and held it up to the mount holes on the fork leg. Looks like that dimension is the same so the caliber should mount. Whether or not it's the correct offset or not, I don't know.

I measured my fork tubes and they are 35mm and ~31" long as well, so they would likely fit a 750. However, that's a bit more involved than I wanted to get right now, not to mention I wouldn't be able to afford the shipping costs on all that.

As for piston movement, don't worry about it. Wouldn't hurt to rebuild it anyways probably. I'll PM you.

 

[Grimly]

Only thing I found as a gotcha was the L model forks have a different caliper mounting bracket, because of the axle position and the placement of the caliper on the disc as a direct result of that. However, the caliper is the same, so acquiring another pair of standard caliper mounts sorted that out.
I'm not even sure the 750 35mm fork legs even had an L model to muddy the waters, anyway.

 

[93Bandit]

Only thing I found as a gotcha was the L model forks have a different caliper mounting bracket, because of the axle position and the placement of the caliper on the disc as a direct result of that. However, the caliper is the same, so acquiring another pair of standard caliper mounts sorted that out.
I'm not even sure the 750 35mm fork legs even had an L model to muddy the waters, anyway.

That would make sense, the differences between G and L due to L axle placement.


Roger is sending me all 3 calipers from the 650G. I will be sure to update the thread once they arrive and are installed.

Thank you again to all those who helped out!

 

[93Bandit]

The calipers Roger sent me arrived today. I'm under the weather so won't be able to check fitment for at least a few days, but I'll update as soon as I get the chance.

 

[93Bandit]

Finally had a chance to get back on the 750 yesterday. thought I'd update this thread in case anyone in the future needs the info. I test fitted the 82 GS650G front L brake caliper on my 77 GS750 and it fits perfectly.