KH Laser burning oil (sometimes)

[Peter B - CV8]

First post - so take it easy....
My son has a KH Laser, 1.6 litre carby model. It has done about 185,000 k's.
At cold start up, it used to regularly have a sticky lifter tick - but a dose of Nulon "Lifter Free" seems to have cured that problem.
Just lately it has been occassionally blowing a fair bit of oil/smoke - usually when taking off form the lights (after having sat for a minute or so idling). It doesn't last long - just 10-15 seconds then clears up. It also did it once when just sitting idling in the driveway.
I'm pretty sure that its up for a set of valve guides & seals. Anyone else had this problem - or give me an idea of part costs $$ (I'will change them myself as I'm pretty handy & it looks fairly straightforward).
I'm also thinking that the "lifter free" additive was too good & maybe dissolved all the accumulated crud that was possibly sealing up the valve guide previously.