When you say "MX head" do you mean "MX cylinder and MX cylinder head"?

The reason I ask is just using the MX cylinder head on a stock cylinder will give you way too much compression... not a good idea.

I appreciate the info. I’ll start trying to source an Mx cylinder.

Armature came off with no drama thanks to all the tips I’ve read on this site. Time to replace the seals.

Make sure the crank bearing doesn't have play...

Consider using the better IT175 crank seal with proper dual lips to seal pressure and vacuum.

No play in the crank bearing and I did get the oil seal from the IT on order, PN 93103-25125-00.

Now I just need a decent MX cylinder. Found some possible NOS for $400ish, yikes. There's one on ebay with a crack and a bent fin for $300 plus shipping, double ouch.

I'm in no rush though, still have plenty to do. Once I get the bottom end buttoned up I'll move onto the fuel tank. Somebody (my dad) creamed it back around 1991 so I'll need to dedicate some hours to it.

I may just end up going with a 175 top end.

Got it all torn down at this point. I’ll be sending the frame, swingarm, and some other pieces to my brother for sand blast and powdercoat. I will likely start on removing the cream from the fuel tank next, or possibly start rebuilding the suspension and wheels.

The free bike just cost me a $500 watch. That’s an expensive learning lesson. Could be worse.

I’ve been able to piece together most of my top end. The cylinder head is new old stock but the cylinder needs some work. There’s a surface crack and at least one bent fin so the cylinder will go off to my master fabricator brother to fix that before addressing the bore. I also have a GYT expansion chamber showing up this week.

Unfortunately UPS has lost my GYT expansion chamber. They're "looking for it" but I've heard the same thing for a couple weeks now, so I'll probably start looking for other options soon.This really took the wind out of my sails.

I've been trying to reach Racer's Machine to have the cylinder work done but haven't heard back. Might end up sending that up to my brother's shop too, I don't know at this point.