1978 GS750EC Caliper Piston source?

[Soto]

Looks like my front pistons are very slightly pitted around the base.
This looks to be the OEM pad and piston set:
59100-44823

I already have pads and seals, does anyone just sell the pistons and have stock or a perfect fit?

I've checked about the first three pages of google results and a few places mentioned on the forum. All seem to be out of stock.

I would be all over the salty monk upgrade if I had any metal working ability where I am at. Bolt-on caliper upgrades would be seriously considered. In case it matters, I have cast wheels and solid rotors, both original.

 

[Nessism]

You may have to order from the UK. They have aftermarket (pattern) stainless steel pistons over there. Check ebay.

 

[roeme]

I've found pistons on wemoto; thankfully, the pitting on the pistons I had did not extend to the seals.

Maybe show us a picture of your pistons, they might still be good. To my knowledge, the corrosion will not extend if you keep your brake fluid in good nick.

 

[Soto]

Here they are after cleaning. The bottom of one has some very light pitting as well.

 

[Sandy]

While new ones would be ideal I'd check the surface area where the seal will be actually contacting the piston. If it's good there just dress the rough spots so there's no chance of tearing the seal when you reassemble.

 

[roeme]

View attachment 55823
Here they are after cleaning. The bottom of one has some very light pitting as well.

Bottom pitting doesn't matter. About the pitting visible in the picture, I'm not sure. Right one seems to be a bit too close to the sealing area, Left one could work. Maybe someone more knowledgeable on this model could chime in.

 

[allojohn]

Continuing to use those pistons may be OK but you'll won't really know until they start leaking - when will that be?
Wemoto carries stainless steel pistons, put them in and forget about it....

 

[Sam 78 GS750]

I clicked on this thread to recommend Wemoto as well. I see a couple of folks already beat me to it. Their website is a bit rough to navigate, but their customer service is top notch.
I have the same bike and just went through the same thing.

Make sure you order 38x40mm pistons. The 77 and non E models used the same smaller pistons up front as they did for the rear.
I ordered and got the wrong pistons the first time around. Not a problem, I just used them for the rear calipers... That's what I mean about the website being a bit rough to navigate. Send a quote request first and specify your bike and 38x40mm pistons.

If anything, just call 01273 597072 (international, may have to use the country code for UK)
Ask to speak to Nick.

 

[Soto]

Thanks for all the advice folks. I put in an order with wemoto.

 

[Steve]

I see you have already ordered, but you can also check with one of your neighbors. :-k

GSR member Chuck Hahn is just up the road from you in Norman. :encouragement:

.

 

[chuck hahn]

Wemoto or K&L Supply are my go to guys. And yes i am about 10 miles from you.

 

[Soto]

I am a new rider, just got my endorsement and training course a couple months ago. I could push the bike with the front brake held when I bought it. One thing led to another and now every front brake component is being rebuilt. The master cylinder had no intact rubber in it. Suzuki rebuild kit is already in the master cylinder. K&L kits are already in the scrubbed out calipers. Hel brake lines - I either bought the wrong kits or they sent me the wrong thing so I'm waiting to hear back from them. I bought the bike in OKC and that is were I'm working on it in a friends loaned garage.

It looks like you are a mechanic, Chuck. I'll certainly keep you in mind as I'm going.

 

[chuck hahn]

Or you can bring it to me and we can sort it together. I would take all the lines off and go see Sherrie at central Oklahoma Hose and have her make new ones too. They can usually make them as you wait. She makes all my lines for my own bikes and customer bikes. Gonna run around 70 bucks or so.....

 

[Sam 78 GS750]

Or you can bring it to me and we can sort it together. I would take all the lines off and go see Sherrie at central Oklahoma Hose and have her make new ones too. They can usually make them as you wait. She makes all my lines for my own bikes and customer bikes. Gonna run around 70 bucks or so.....

That's really good. Even cheaper than building your own...

 

[Soto]

On the topic of wemoto pistons. They are telling me they have two sizes that are close:

"1 measures 37.98x41.00mm and the other measures 38.09x40.00mm."

I assume it is the 38.09x40 as that is closer to tolerances in the manual. I ask which because neither is within the service limit of 38.105.

On hoses, I will certainly check out Central OK Hose. Hel customer support isn't responding to my emails

 

[Sam 78 GS750]

The 38 x 40 will be fine.

 

[Soto]

The 38 x 40 will be fine.

I basically copied your advice from before along with service info and they think they have it figured out now. Thanks.

They won't ship until sometime in the next couple weeks.