Rear Shock leaking HI just looking for some advice , i own a xr400r 2005, and been with the bike to hell and back i mean this workhorse been in some tough terrain rock climeing were even KTM ‘s could not make it - belive it or not. Anyway got holidays in a week and wanted to bring my good old Honda xr to life; predicting i got a leaking valves/head gasket as its not making the power as it used too. Or maybe a dirty carb which needs a clean too! from 5 years of punishment many parts are taking itheir fate, recently saw very fine oil leaking traced it to the rear shock absorber... I rebuild engines before but never touch suspension so its black magic , so need some help. Now i understand fo r a full service (regassing) with nitrogen a pro needs to do that as special tools are needed. But in my case looks like the O-ring/seal leaking... 1. Question is , can this seal and refill of new oil on the shock be done easily - or do you need special tools to compress the spring or to compress the piston? 2.otherwise if i got a pro to do a full service (oil change seal and nitogen re-gas) how much roughly am i looking it at $? 3. for future reference if a head gasket will be replaced what is the best way to clean the old gasket surface? I want it to be 100% sealed no leaks! Is a 600-800 grid paper enough or is it a must to get it shaved?but dosnt this lower the compression? If thats the case a shave is not for me as i don’t want to upset the squish level , anyway how much does a shave cost or a mill or whatever it is called to machine the surface before gasket application ? Appreciate the help..