well update, I was concerned that the throttle didnt snap shut when I assembled the carb. I suspected the spring in the new sps valve was holding up the needle slightly.
First ten or so kicks all I got was a backfire. I gave up went back to work. Got home tried again, sparked into life easily but weirdly when I used both choke and hot start valve at the same time. My KTM does the same. Got it hot, starts superb and no spitting back so all in all its been a worthwhile mod. However the throttle is still not shutting completely, I have ordered a new spring, gonna try two to prove it and will try finding one slightly stronger. (Currenty ticks over at about 2500 rpm and runs on when you close off. I am sure its easy to fix in the morning. I reckon it has cost me 120 inc the hot start valve and sps bits.
One thing, if anyone else does this make sure you get all the bits i.e. the hot start valve came with no spring...the drain plug no o ring...frustrating to say the least. Overall the niggles pale into insignificance when you can just prod the kickstart when hot and it fires up!
Bring on the next trial.