86' WR 400 piston needed

1st, let me introduce myself. My name is Jim Lundgren. I am a retired electrician,
66 years old. I have been sporadically involved with off-road motorcycles since 1971.
I am a casual trail rider here in the Pacific N.W.
I have been repairing motorcycles for the las 12 years. Mainly, IT Yamahas of every displacement,
and RMX 250 Suzuki's. I once owned a 78' 390 auto that was troublesome, and at the time I was too
stupid, and broke to maintain it. But I have fond memories of how it handled. I ended up frying it in the dunes after spending a lot of money on the transmission! I no longer go there!
So recently, I bought an 86' WR 400 for $1600 that started on the first kick, and seemed to run well. None the less, my past experience, and a little birdie, told me to tear it down for a look-see.
What I found was that the piston had been seized, and is in need of the next oversize re-bore.
The piston is an 82.92mm Mahle, in a worn 83mm bore. The reason for the seize was obvious. The P.O. had slobbered the head gasket with silicone goober so much that the water passages were effectively blocked. So, long story short, I'm needing a piston for the next size (assume) 83.5 bore. What my problem is that I can't find one! Can anybody steer me in the right direction?

Welcome to the cafe.
Love the 400 motor.
Here is a nice shop to deal with.

https://www.husqvarna-parts.com/catalog/item/3736875/7735248.htm

Thanks, I looked at that site before looking for chassis bearings, but must have missed this.
I found some shop in England, and they said the new deck height is .017". Mine is about .006" measured with a feeler guage. I also did a solder test, and found my squish to be about .040, which is about 1mm. The last engine, I can remember running this well?(ran and started) with this much wear was a 50's Chevrolet 235 six! My nickasil bikes wouldn't even kickstart at this point.

Your deck height can be adjusted by using thin or thicker cylinder base gaskets. Usually, you will need to cut your base gasket out of material the correct thickness. Head gasket thickness is pretty much what is available.

Marty

Cometic will make gaskets in any of their available thicknesses. I have done this for the 430, 250, and 125/175. I've not asked them about the water coolers but, if they have the gasket dimensions in their database, they will crank them out in any of their usual thicknesses.