These Evos are pretty dependable bikes, but with age and mileage things need to get addressed. About 40K miles ago, I did a base gasket change and most gaskets are still holding up. The lower rocker box gasket on the rear cylinder began to weep, then leaked several months ago. Finally, I decided to take care of it. Parts are still readily available at the dealership. All four gaskets were under $20, and it took an hour to complete the job.

Some important notes:
1. make sure the cylinder you are working on is on TDC
2. rear top rocker cover on some bikes will need an Allen key shaved down a bit to get between it and the frame
3. torque sequences and spec are crucial so not to warp the rocker box, because they are prone to warp
4. the top cover rubber gasket from H-D was still a tad off, but it's workable, if you ensure the lower side is on right. A little off on front higher side is OK, when torqued down. Maybe other gasket makers are better.

Keep those Evos on the road...and safe riding!

 

What are torque specs please ?

 

Depends on which bolt you are talking about.
The 1/4-20 have a lower torque than the 5/16-18 bolts.

I don't remember off the top of my head but that information is readily available in your factory service manual.
If you don't have one and plan on working on your bike yourself then you need to get one.