First time slide stuck was hard to get it out. Slide and bore looked fine. It went back in with no problem. Rode bike then it set up a few weeks. Slide stuck again. Flange bolts not over torqued, flange on carb looks true not warped. Any idea of what else to try? Strange thing is once I fight to get it out it will slide right back in like new.

Was going to suggest everything you said is Ok so i dunno. Is there something unusual going on with the slide guide. No anodizing coming off the slide. Try a little bit of oil mix in the fuel. Had that on my DT2 on methanol in vmx & the anodized slide would stick but was running castrol mssr oil through the pump. So mixed it totally in the fuel & all good.

What grade petrol are you using?

Even if left for just a few weeks, modern petrol can degrade and leave sticky deposits. 

Thanks for suggestions, going to check the guide on slide again and try what you mentioned with oil/ fuel.

Been using non ethanol fuel. Going to work on it this weekend 
and look over everything again. I’ve never had this happen 
on any bikes I’ve had. Thanks for replying.

Could back off the flange bolts a 1/4 turn even though not suspected. Doesn't take much to stop sticking if related to that. If there's an Oring set into the flange it'll be safe from drawing air in. Favorite trick was finding an Oring too fat which warps the flange ears & carb body/slide area. Wonder if the fiber spacer can compress warped & pull the carb ears trying to match it. Spacer is quite thin on those not like piston port earlier 'i think' so unlikely. I know ya say all that's ok, but anyway, i'm clutching at strawers at the mo. If its only right at the top maybe get some fine emery in there on your finger & ease the carb body a bit above the guide pin area.

Thanks for suggestions. I’ve thought about 
what to mentioned. Slide and bore look fine.
Its got to be the torque on the carb flange bolts.
I’m going to try less torque and see what happens.

Have you actually measured the slide to make sure it's perfectly round? I keep seeing  mention of tightening the flange bolts making the carburetor warp, but it's hard to picture that happening with cast aluminum.

Carb warp slide sticking  is very common on these bikes if someone has overtightened flange and/or used wrong o-ring. 

I'll definitely take your word for it MarkT, but it still might be a good idea to measure the slide to make sure the measurement is the same no matter where you put the digital calipers. May have been mishandled at some time over its life.