I just replaced the head gasket on this xplorer 400, started it up, it ran a couple of seconds and died. The spark plug was fouled. I cleaned it up and tried again. Same thing happened. Took the head back off and there is a film on top of the piston that is brownish like oil, but not sure. What would be causing this?

 

Probably needs a new top end,but the best way to tell is when the engine is assembled and do a compression test. Less than 100 psi,time for a top end. Plus if the head gasket wasn't torqued down properly could be the problem,plus a warped head or cylinder can cause coolant leakage into the cylinder from the head gasket. Once you removed the head,the new head gasket isn't worth installing again to accurately test! Plus a leak down test is the best way to tell where the problem is also.

 

Thanks for your insight OPT. I am just wondering where the brown liquid film is coming from that is inside the cylinder as I still have the coolant drained out of the engine.

 

Not a good way if you started it up without coolant if I'm understanding you correctly? Plus the 400 engine could warp heads which could account for the brownish liquid on top of the piston(seeping coolant through the head gasket into the cylinder),OR could just be crank case residue pushed up from the bottom of the crank case into the transfer port then to the top of the piston. Always bleed the the 10mm screw on top of the head located close to the coolant temp sensor when you add coolant or trapped air pockets in the coolant can causing the engine to over heat quickly,blow head gaskets, over heat and warp the head,cylinder or both. You may want to have the head checked. If it is warped you can have it milled down about .010 and that usually takes care of it.

 

Thanks again!

 

So I'm pretty sure the brownish liquid that is present in the cylinder and fouling the spark plug is coming up from the crankcase. Would that just be residue from when the head gasket blew and I need to flush it out ? Or is there something else that might be causing that? Thanks.

 

Could just be residue,plus head gaskets can blow for several reasons. If not torqued down properly,over heating can blow one quickly along with a warped head or cylinder or cracked coolant passage in a head or cylinder. That's where magnafluxing comes into place. Very easy to find with the dyes they use to find small cracks. Hopefully you can just flush the crank case with kerosene or naphtha,use 2 stroke oil to lube up the lower rod bearing and crank bearings and have another go at it,but wouldn't take long to have a machine shop to check the head and cylinder for any warping,plus even check for cracks if you've blown more than one gasket.Cost shouldn't be much on this and could give you peace of mind on reassembly if in doubt. Plus an old school way of checking/cleaning heads and cylinders was to have a good flat surface,600 or higher grit wet sand paper and just do figure 8s with the head and cylinder. If all spots are shiny,no dull spots,then the head/cylinder shouldn't be warped.