LT50 drivin me nuts

[FROSTY:Me]

Ive got a LT50 in my workshop for the 5th time.
Darn thing is drivin me nuts
Background.
A quad turns up here -we pull the lead n barrel off. we decoke the ports rering,clean out carby,check axle bearings etc. basicly we send out a reco'd engine
This one bike though is nuts
Same story every time.
Bike arrives customer not happy -bikes not going
Plug out, Carb off,check all the settings. Check for crap in fuel etc.
NUFFING
Bolt back together pull the starter and away she goes.
Give bike to resident quad tester -half an hours rideing all good.
Customer takes bike away a week later back--bike no go,
Story goes bike was ridden for 4 days and "just died"
any ideas???

[xwhatsit]

You must have pretty slow nuts then.

That's like what my bike used to do when it had weak spark. Once it was hot it didn't want to idle right and wouldn't want to start at all. Pull out the plug, put a new one in, it would crack up straight away. After I did that a few times I thought I'd stick in the same plug again -- it started again anyway! Needed a fresh charge of air in the cylinder (just take the plug out) and let the plug cool down to where it would spark easily again. Of course making the method of tracking down the problem a real bitch, as all it was was a weak spark problem manifesting itself in poor hot running.

[Ixion]

I presume you try starting it yourself before stripping?

One (obvious) idea, next time remove plug only, replace, try.

Then remove carb only, replace, try.

Maybe a dodgy earth somewhere, temporarily improved when you repalce various bits? Or an air lock in the fuel line?