I have parts on order for what will hopefully work and be how things will be. I have some 1/16 NPT compression fitting with 1/8" copper tubing on order. This tubing should easily form and bend to a remote fitting location with the grease fitting installed. I have these parts ordered for the twin so there is a tee fitting to combine them. Other than that fitting the single cylinder engines will have the same parts.
All you would have to do pull off the head and then drop out the intake valve. You will need to find a location you can drill through to hit the bore of the valve stem somewhere in the middle of the length of the bore. Start out with a small drill 1/8" and drill through and then send a drill that is sized for the 1/16 tap, dont go all the way through with this one but far enough to drive that tap in about half its threaded length. Once you have the hole drilled drive the tap in and then install the compression fitting. If you have a tight space you can simple get a 1/16 nipple to extend this out and get a couple to install the fitting. Then simply install the copper tuning in the fitting and route to a convenient place that you can skirt some grease in there.
You may need to debur the bore for the valve after this. You can do this carefully with a slightly smaller drill bit doing so by hand or a small rat tail file. But you really need to be careful you dont scuff up this bore. If you know the bore size and have few bucks you can get a reamer but again this is something that should be done by hand carefully.
For a few hours of work, if that; this mod is definitely worth the efforts to never have to worry about tar again. If we have good fuel the machine should never make tar but that potential is always a posibility for us, especially with new users. Ive see it all lol and for us at least this will get our new users through learning and to engine running faster. The machines also need to burned in for quite a few hours before they will make the cleanest gas. This again will aid to getting to that point with confidence.