What is the problem you are having with the bike? The reason I’m asking this is because you stated that your were having trouble with the clutch “engaging“. When you pull in the lever on the clutch you are actually trying to disengage it. If the problem is that the clutch is not engaging then I would think it is more a problem with the clutch itself. The clutch plates may be stuck open, or the slave may be stuck and holding the clutch open.
If the clutch is staying engaged and not disengaging when you pull the clutch lever (more likely to me) then it could also be a number of things. The clutch plates could be stuck together. You could try letting the bike warm up good and try riding it working the clutch to try and get them to separate. Most likely if you haven’t ridden it for a while.
If the master cylinder reservoir fluid level goes down without seeing a visible leak then you could have a leak at the slave. There are 2 o-rings that could be leaking.
You could have dirt or some other contaminate in the master cylinder and causing the plunger to lose its seal and keeping it from building pressure.
The worst case would be that the clutch fingers are bent and not opening the clutch or the clutch plates are damaged .
There are rebuild kits available for rebuilding your master cylinder and slave. They also have kits to convert older bikes that use brake fluid for the clutch to a system that uses hydraulic mineral oil system.
I know its a lot but I hope this helps.
