Front Wheel Brake Master Cylinder Reservoir Size

[Mr.humbucker]

I am working on bringing a GS650G 1982 back to life and instead of trying to rebuild the Front brake master cylinder piston mechanism etc ( which was a mess) I ordered a complete front wheel master cylinder replacement (cheapo) on eBay (which I have used in the past with no trouble). I completely disassembled the calipers and cleaned them from stem to stern before reassembling them. The new eBay front handlebar master cylinder reservoir seems small to me in comparison to the stock unit. i should add i have not compared the volume/capacity between the two. The piston bore is the same as the stock original, 14mm I believe. Is there a need for the reservoir to be lthe same as the stock unit or should I be ok with what I've received?

 

[Nessism]

I think the master should be 5/8", not 14mm, which is used on bikes with single disc systems. And if the master got all full of crud, you can be assured, the brake lines are now lined with it also. Time for new lines.

 

[Mr.humbucker]

I think the master should be 5/8", not 14mm, which is used on bikes with single disc systems. And if the master got all full of crud, you can be assured, the brake lines are now lined with it also. Time for new lines.

I have ordered the 5/8ths unit and will send the other one back. Thanks for you input!

 

[Sarcvicious]

I am working on bringing a GS650G 1982 back to life and instead of trying to rebuild the Front brake master cylinder piston mechanism etc ( which was a mess) I ordered a complete front wheel master cylinder replacement (cheapo) on eBay (which I have used in the past with no trouble). I completely disassembled the calipers and cleaned them from stem to stern before reassembling them. The new eBay front handlebar master cylinder reservoir seems small to me in comparison to the stock unit. i should add i have not compared the volume/capacity between the two. The piston bore is the same as the stock original, 14mm I believe. Is there a need for the reservoir to be lthe same as the stock unit or should I be ok with what I've received?

Any updates? Did the cheapo MC from eBay work out? I have the same bike and am looking for a replacement part

 

[Mr.humbucker]

Yup it works great. Matter of fact I went for a rip on it today and it worked great. I have new braided stainless brake lines on it and stops great. Interestingly I am now restoring the parts bike I had picked up for the bike I mentioned in this previous post. It too has an eBay cheapo brake master cylinder for the front. I am just finishing it up and will let you know how it works. The reservoir is smaller than the stock but this does not affect the braking power ... You just have to keep your eye on the fluid level in case it gets low you don't have as much "extra" or surplus fluid to play with.
Hope this helps!

 

[rphillips]

interesting and good info. I was very skeptical appx. 3 yrs back. We got and installed one of those cheeep $20 ebay ones for a friends CB1100F. The fit, looks, and function was was spot on. I couldn't believe he got that quality of part for $20. Whole new master cyl. for the price of a rebuild kit.. Go figure.

 

[Mr.humbucker]

Ya they're actually cheaper than a rebuild kit. It was hit and miss as to whether the rebuild kit would work for me as often there is unseen corrosion in the body of the old device and they'd eventually leak.