Another top-end Q

[bowhunter007]

I am prepping to pull apart the top-end of my 250. After disassembly, and inspection of all the parts...Do I need to measure the head gasket thickness? Every other motorsport has offerings for head gaskets, in order bump or tame compression.

 

[Rick]

Head gasket are o rings. Measure your base gasket(s). There could be more than one, they can be stacked together to achieve proper height so it is important to inspect closely.

 

[bowhunter007]

Head gasket are o rings. Measure your base gasket(s). There could be more than one, they can be stacked together to achieve proper height so it is important to inspect closely.

Thanks. This'll be a whole new experience, so I bought a notebook to keep track of every little thing.

 

[Jakobi]

Get the verniers out Measure the squish clearance as stock and then measure the base gasket stack. Investigate the pistons location at bottom dead center too. Then you'll know how much room you have to move to make adjustments.

 

[bowhunter007]

Get the verniers out Measure the squish clearance as stock and then measure the base gasket stack. Investigate the pistons location at bottom dead center too. Then you'll know how much room you have to move to make adjustments.

When I have the jug off...What sort of wear or damage am I looking for specifically? I have never worked with engines with the N----(whatever it's called) coating. I'm going to take pics, as I go, so I have visual references. I'm actually looking forward to see the differences between a coated cylinder vs uncoated, as far as wear i.e. ridge wear, hone marks. Does one hone a coated cylinder? I haven't reworked a 2t engine since my 1976 KX 400, and that was 20+ years ago.

 

[hannesd]

if you find some coloured spots in the NICASIL layer then that might not be so good.
allso scuffing marks from the piston like with a seizure from for example lean setting, hard abuse, lack of oil...
honing can be done by hand with a scotch brite and some diesel oil or some light oil to make some new cross hatches.

look for small cracks around ports.
if you have an older cilinder, you could find some, but hopefully you don't .

if something's really wrong, you''l notice,i guess.

 

[desertgasser300]

FYI, your KX250 will have a nikasil coating also. You will prepared for that one with the Gasser.