Join Date: Aug 2013
Location: Sale, VIC, Australia
If there's coolant in the oil, and compression is a little down on one side, it's possible the bike may have done a head gasket. Though if your measurements are in PSI, anything over 110 should still be sufficient to run.
I'd also check the water pump seal to the motor to see if that could be the culprit of the water in oil situation.
The loose exhaust rocker could cause an issue if the valve on that rocker isn't opening properly. If you can, swap the one from your other engine onto it, and see if that works?
Clean the carbies too, or while you have them off, squirt a bit of fuel straight down the inlet manifolds and wind it over, if it starts on both cylinders for a second or two, it might just be a carburetor issue?
Also: replace the plugs, if you haven't done so already. Some times it's as simple as a spark plug that's decided it doesn't want to spark any more?
If still no go, I'd be inclined to remove the head and check the gasket there...
Fork seals aren't usually a difficult job, but for a proper finish are often best left to a mechanic who can hone the fork legs and install the new seals carefully with the proper tools. They are VERY easy to damage if you're too rough installing them. But if you're so inclined, give them a go? There are a number of videos on YouTube that can give you a good how-to.
Hope that helps!