I used copper ones on my CT1 which haven't sealed 100% (it's on my snag list), on the plus side I have auto chain lube

I know what you mean. On my RT1B I finished in the summer my new Yamaha fibers leaked a little. But after three additional tweaks with the wrench (I had to come back at it three times due to still leaked) it stopped. It got to a point where I thought man am I going to strip it! Get those mating surfaces super clean and tighten her up.

Edit...I also bought the correct thread tap and cleaned all the old gunk out of the threads before a good tightening.

Thanks all, I have tried a lot of the same things with no luck. I will try the McMaster Carr and getting the surface clean.

Mike

Don't forget about DEET... it's likely he has what you need as well... Harbor Freight option looks good too.

Will do on Deet, I have tried the Harbor Freight option. BTW, I have this problem on two bikes, I had replaced them many times with the old gaskets, so I know how it should be done.

I mentioned Harbor Freight again because it's easy to miss a post on here sometimes... at least for me... and I know you know what you're doing... I've seen your bikes at a few events over the years... love them... even... actually especially... the non-Yamahas.

On that old post from 1971DT250 that mentioned McMaster-Carr there was something missing... might be worth reaching out to him and see if he can fill in the blank.

Sometimes those little seeps and problems can be the most maddening to fix.

Thank you for the compliment Mark, much appreciated especially coming from you!!!