Hi yes i meant the accelerator pump diaphram, i am going to recheck valves ,tappets etc . thanks for your suggestions they all help.

Sorry if what im about to write sounds complicated so ignore it all if ya want.--.If you push the kick lever down to get past where the decomp releases then bring the lever up a little but but not far enough to activate the decomp again then push it down from there to feel full compression, if it feels positive then tappets should be ok for this test--ie, chasing starting issues. At TDC on compression stroke if you have clearance to feel by hand on the decomp lever at the tappet over then you'll be safe for now. Then it's back to the carb I guess. That reminds me, I think it was those I've seen the carb manifold come un-bonded on the alloy stub so wriggle the carb & would be very obvious to see. I had a wire out inlet lobe on the cam on mine which didn't affect starting but made little power. I'll find a pic for a laugh. Didn't rattle as wear was on the lift, not the back of the cam. 

Rechecked the valves again & found the exhaust valve was fine but the inlet/intake was way out so much so i do not think it was opening at all , readjusted & starts first kick now , so i am taking this as a win .Appreciate all the suggestions & help.

Umm, ok. I'm sitting up & taking interest. Wish we had pics but never mind. I'd be worried why it was So Far Out or had it pounded the tappet screw away. I must post a pic of my worn inlet, you'll laugh. But my wear was on the lift side not the back side where tappets are set.

Oh i am sure this was an error on my part when i set them during the engine rebuild .

My TT cam showing inlet lobe wear. Must've been made out of cheese lol. Inlet was only just lifting. Ran perfect but no horsepower, not even pony power, just gutless. TT's had a problem with the CDI box blowing the advancing part of the electronics & just stayed retarded. I replaced probably 3 at work over the time TT's were popular. My one which "was given to me" ran verymuch like the CDI box problem but was happy to find the cause after a bit of head scratching as didn't rattle at all as tappet setting was good on the back of the cam where you set it. Anyway--different to your issue & happy you've solved it at last.
photos.app.goo.gl/Vvo17xv7GkgEZ8gY6

I like the look of the 250 TT side plastics better than a standard XT, not a common bike here in the UK if i remember rightly , it was the DTs that everyone had including myself , a red DT50 with a 80cc big bore kit on it good times.

Took bike out for a test ride & rode ok & gears all work but the bike is sluggish and not accelerating as it should , didnt seem to want to go over 40mph , ive checked for vacuum leaks and done the valves so does anyone have any suggestions.