This has an inverter board controlled carb with stepper motor, it's running rough at high speed, running it with the carb motor disconnected is the same so it looks like it's not a fault in the electronics, I have cleaned the carb but it wasn't dirty, can anyone advise on where the high speed circuits are and how to get at them , I'll need to double check every circuit. 
 
The spark on this machine is very weak and it's not CDI , I have ordered a new coil , we'll see if it makes a difference. I can't find any specs for this engine but the valve clearances are ar 5 thou when I got it. 
 
https://toolshouse.co.uk/...b9chZLYj8aAjN7EALw_wcB
 
 
 
Also noticed the spark is very weak for a non CDI ignition and the underside of the cylinder head outside of the cooling air stream where the push rods are  is running at  80⁰C , I've not noticed this on other small engines. 

Remove the carb and then the float bowl.
 
The main jet could be several places.  It could be in the nut securing the bowl on OR
a very small jet screwed into the side of the protrusion that the float bowl attaches to (probably this).
 
It MAY, if the main jet screws in from the very bottom, have a removable emulsion tube (which clogs often).  That extends into the main venturi.  You should be able to push it down and out from the venturi.   
 
The suit case carbs often hides the throttle and choke control  (fly by wire) connectors so you may
have to work very close to the engine.  
 
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The carb on this is spotless and has been stripped and cleaned but it's still running rich, electronic throttle control has been isolated and the problem is still there with manual throttle control. 

Try un-bolting the carb from the engine and supply fuel thru the fuel line to the carb.
 
If the needle / seat / float aren't working correctly that could result in a rich condition.
 
Also, PU a spark tester and plug it into the machine while it's running, if spark is NOT always
present, you should see it on the tester. 
 
If there indeed an issue with no spark, that ALONE can make it run rich (it's not burning the fuel the engines sucking in..
 
The below tester, or similar is very inexpensive.
 

I am having another go at fixing this , I have isolated all the electrics, oil switch, inverter board , carb stepoer motor ,  run the engine over with a drill and there is a continuous spark , there is enough compression , i have checked the pushrods and clearances, the carb was hardly used and clean but I stripped it and blew every passage way out with carb cleaner, the thing won't run in any position of the throttle or choke now, it will fire over with East Start though. 
 
 
 
Can't be anything but the carb but there are no parts for this engine and its not one of the generic Chinese carbs on eBay . 

What's this mean:?
 
Quote:
it will fire over with East Start though.   
 
End quote.
 
What's Easy start and what's "fire over"-  Spark at the plug, engine now runs, ????
 
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Waterworks
I am having another go at fixing this , I have isolated all the electrics, oil switch, inverter board , carb stepoer motor ,  run the engine over with a drill and there is a continuous spark , there is enough compression , i have checked the pushrods and clearances, the carb was hardly used and clean but I stripped it and blew every passage way out with carb cleaner, the thing won't run in any position of the throttle or choke now, it will fire over with East Start though. 
 
 
 
Can't be anything but the carb but there are no parts for this engine and its not one of the generic Chinese carbs on eBay . 

This was a mistake, I've just found out that the fuel has been contaminated with Diesel so back to square one. 

Well that's an easy fix!  
 
Tks for the update

I've found the original fault on this by a process of elimination,  the rough running is stopped by shutting off the fuel tank and running just the fuel in the carb bowl, the needle and seat are in perfect condition so that only leaves the float (which isnt leaking) not rising enough , older floats had a metal tang which could be bent but this is all plastic ,no parts exist for this engine so I'm gong to have to find a solution , anyone solved this issue before ?
 
 
 
 

So the float, at it's highest point (carb in operating position) is too close to float bowl?
 
It obviously should be level the the carb body when inverted (needle closed).  
 
Just to confirm, the float with the needle closed, hangs down too far, correct?
 
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