I am communicating with FFR about my hyd reservoirs (3) leaking around the neck.
I have 1 for the front, 1 for the rear brakes and 1 for the clutch. They all 3 are leaking around the neck. I have read about this issue prior to mine manifesting itself, just now go carting.
My caps are also unvented.
Since I may or may not end up using the leaking reservoirs, I wanted to let others know my plans to vent the caps.
Small engine shops, lawn mowers, etc have a part called a duck valve. It has butterfly lips that will vent one way. It is made of a silicone like rubber and is less than 1/4" in diameter.
I have plans to drill into the side of the reservoir cap, then drill an intersecting passage from the bottom. The duck bill valve will be installed and secured in the side passage.
This valve will let air in, only under an internal vacuum.
I paid 2.39 for the valve at the local shop, probably buy 10 of them off the net for that price.
I did drop mine in a container of brake fluid, so far, so good.
The one I bought looks like the OD green ones at this site.
Hope this helps those stuck with the old bad design reservoirs. I think it will be the perfect mod to prevent issues.

https://www.google.com/search?q=smal...w=1280&bih=584