77 GS750 Rotors

[Guest]

Hey guys, just wanted to see if anybody had a good source for new front and rear rotors for my 77 GS750. I can't seem to find anything for less than ~$300 - $400 and am hesitant to buy a used one off of Ebay, as it may be just as ridged as my current rotors. Are there rotors from any other new bikes that anybody has used as bolt on replacements or am I going to need to call in a favor over at the machine shop? Thanks again.

[GreaseMonkey]

I'd love to hear some info on this as well. It seems like every restored GS I see has the fancy drilled rotors and I can't seem to find ANY new rotors for less than a few hundred bucks each. This blows my mind since car rotors are $25-50 in most cases, but I guess that's the difference between a cast part and one with a machined hub.

Also, can the stock rotors be resurfaced? I've thought about throwing them on my brake lathe, but I've been hesitant to remove any material since they're so thin already. I can shave a few thousandths of an inch at a time, but I don't want to make my rotors unsafe.

[Ghostgs1]

Rotors can be thinned on a lathe just don't go below the min spec for thickness. I don't have the specs for a '77 750, but the '79 1000 E and S are 6.5-6.9 new and 6.0 min. Should be able to pull a manual from Basscliffs site to find info needed. If they need replacement, I would check EBC on line they list all the old bikes up to the current
models. Ray

[Big T]

Bike rotors should be surface ground, not turned (so I've been told)


You should just check the GS marketplace

[Ghostgs1]

Surface grinding would be the best option, if you have it available. Using a lathe can work if you know what you are doing. Not an automotive rotor machine. A real lathe.

[GreaseMonkey]

Sounds like my trusty brake lathe may not do the trick. Part of me would like to throw on some fresh bits and try to cut them in .001" passes, but another part of me thinks that would be an expensive lesson to learn. Do motorcycle shops offer surface grinding as a service? I'm not having any issues with my brakes at this point, but I'm replacing the pads so it seems like resurfacing would be a good idea.

[Havoc1231]

The mechanic I spoke to was hesitant to turn or grind down motorcycle rotors because they are already so thin. From what I've read it's been done, but I figure with all the other work I've done to the bike, it would be nice to just replace with new rather than cob up the old. I found two models of EBC brakes which I believe may fit, MD3019RS and MD3014RS. I emailed the company to get specific measurements as I cannot find them online anywhere. Most ebay sellers have them listed as fitting 1978 gs750's but not 1977, however some do show them fitting. We'll see if the company gets back to me with the actual specs. Regardless, looks like they're $200 a piece no matter where I look, so it's time got get out the old credit card I guess. I've roughly measured my current rotors, but if anybody out there has more specific (ie. accurate) measurements handy, they'd be appreciated.

[Havoc1231]

So the frustration continues. I received an email back from EBC, if you can call it that, it was a brief two sentences telling me that the correct rotor model is MD3019LS. After browsing their website again, they have the correct rotors for a 1977 GS750B being MD3019RS for the front and MD3014RS for the rear.

In the original response the rep stated that the MD3019LS was a 296mm diameter rotor while the MD3014RS was a 276mm diameter rotor meant for the 1978 GS750. So now I'm even more confused, as my two rotors (single front and rear) that I removed from the bike are identical in diameter (inside and out). I replied to their email alerting him to the above findings and asked for the specific dimensions of all three rotors (ID, OD, number of bolt homes, thickness of rotor and offset) to which he replied, "You're right!", no dimensions supplied.

I really don't want to spend $200/rotor on something that isn't the correct dimensions and has to be sent back and exchanged. I guess I'll have to get on the old telephone and see if I can get some answers.