YZ Base Gasket

Okay Taffy, an ’00 YZ426 base gasket looks to be eight tenths (.8 mm) thick uncompressed. The portion that goes around the timing chain hole is thicker because it has what looks like an aluminum bead around the outside (this gets squished when installed).

Measurement taken with a good pair of analog calipers so add in requisite margin of error.

thanks hick my faith has been restored.

i measured the WR base gasket as being .020" which is .5mm. the YZ would appear to be at .8mm (.032") even thicker & at the very least the same.

when i switched on tonight i was going to post a new thread so i will just mention it here hick that;

i want to know if the cylinder head gaskets are the same or can you buy various thickness ones like you can with Honda's?

can someone find this out please? i will ask my "lewkl" dealer but expect it to be all too much effort for him.


I think if you'll check the part numbers you'll find you have that backwards. The YZ's are generally in the .020"-.024" range after compression, while the WR's base gaskets are usually in the .031" - .033" range. Based on the engines I've had the opportunity to measure the quench clearance on the early WRs seem to run in the ~ .070" - .080" range while early YZs seem to be in the ~ .055" - .070" range. I've yet to see one that actaully had the advertised compression ratio stock.


i only measured the WR base gasket in one place & it was a genuine .020" with a micrometer.

the squish checked out at .053" using the 1mm solder method.

i would think .040" is comfortable for a nice safe bet yes?


With a tight fresh rod .040" is no problem even with the 94mm pistons.

What is quench clearance? Combined thickness of base and head gasket?

By the way my old base gasket measures out to just over .6 mm (~.024 ”), I’m not sure how accurate a caliper is at that small of a measurement but this is within the range Rich has seen.

quench i'm presuming is the american word for squish. it's the gap between the piston & the cylinder head. the head comes nearest around the outside.

the idea is that it all gets squeezed up into the middle of the head.

so we measure this outside area & it has a minimum of .040" in this case.


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