I'm picking up a 2002 Sportsman 700 tomorrow evening. With I believe a blown head or base gasket.

Few questions, is this a common failure on this model? There's oil in the radiator and the oil is overfilled chocolate milk. I was hesitant to even have him fire it up, but I wanted to make sure it wasn't knocking. Fired up perfect, sounded great with no smoke.

Anyways, I plan on doing head and base gaskets as soon as they come in. Can I pull the cylinder with the pistons still in the bore?

Any tips, advice before I tear into it would be awsome. I'm good with a wrench. Done lots of quad motors, but this is my first 700.

Thanks in advance, slow.

Not a common thing,but can happen. Actually easier to work on the 700 than other models as there is no cam or chain to mess with. Just mark rocker arms so you can assemble back where they originally were,pull the head bolts and remove the head.I'd order new piston circlips as you install the pistons in the cylinder first with inner circlips installed first,lower down cylinder and pistons to fit the rods,insert piston pins and then the outer circips and then seat the cylinder on the base gasket. New head gasket and torque to 35 foot pounds in a cris cross manner.Install push rods and rockers arms. Rocker arm bolts torque to 10 foot pounds. Yes on the cylinder it does pull off the pistons first,but hard to install the pistons on the rod first like other engines because of tight space. That's why pistons go into the cylinder first on assembly. Easier that way.

Hmmmm. Well, this will be the same as the "other" quad motors that you have done.... just has two pistons instead of one ( assuming you haven't done a twin yet ). You will need a manual, do you have one? See below....link. Cost $5 per ATV, download.
https://www.tradebit.com/G/manuals/14-atv

This is my first twin, is what I meant. But looks like it might be easier without the cam and chain in my way.

Again not that hard. Lifters can stay in the block,clean up and gasket residue on the base gasket. Check piston to cylinder clearance once you have it apart. If mine,it would get new piston and rings or at least rings if the pistons are in good shape.Cylinder can't be bored.

What I was saying is that all the other ATV's that you said you have done, unless they were two strokes are entirely the same thing...pretty much, cam(s), cam chain and so on. This really isn't any different, just two pistons instead of one. Don't be worried about it....but don't forget a manual.... You will need.

I got this home tonight but just to late to tear into it, the more I think about it could it be possible its not a head or base gasket, and what are the best ways to diagnose properly.

I mean this thing runs absolutely perfect. Not a bit of white smoke. Just coolant loss into the crankcase.

Thanks in advance.

Best way is to pressure test the radiator and to see if it holds 10 psi. If it doesn't you still could have a small burnt spot on the head gasket allowing coolant to get into the crank case over time even if it isn't smoking. Several different tools available for this from a mityvac pump to using a small bicycle pump with a radiator adapter cap. You can also get cheap pressure test kits at Harbor Freight,Northern Tools or even some auto supply houses can rent these with just a small deposit.

I got this all tore down, valve cover had lots of antifreeze residue in it, as do the lifter area. Head bolts were not very tight at all. Rocker arm bolts were twice as tight as the head bolts.

Its not obvious if either head or base gasket was leaking. They appear intact and I cant see where the antifreeze would have been going through.

Iv read in another thread about the water pump or oil seal could cause an issue, but regardless the head bolts were defiantly not at the proper torque.

Lastly there are a bunch of fins on the radiator that need straightened. Maybe it over heated? I dont know.

Any thoughts?