I'm having serious running problems on a KM 55R that's had only light use (only ever been a back-up). Basically it fires up ok, runs for 5 mins, then bogs under load and dies. After that it's hard to start and back in the van for the day.
I've tried all the usual things: new fuel line, pick-up body, air filter, spark plug; I've taken the top of the carb off, unscrewed the little brass jet and checked that it's not blocked (cleared it out with acupuncture needle). The diaphragm is in great condition and everything looks in pretty good shape. I run Stihl Ultra. Is air getting in somewhere and I can't tell, or is there something else that can go wrong with these carbs that I'm not looking at?
Would a new carb rebuild kit do the trick, or is a whole new carb the way to go?
And while we're on it, can anyone tell me what carburetor (or rebuild kit) I should be getting for a Stihl KM 55R, 2008 model, and how much I should expect to be paying for it. I'm in the UK and I've been quoted nearly £100 (that's $150!) by two Stihl dealers for a new carb (excl. any labour), which is obviously silly, as you can get a whole new machine (KM 56) for £170.
Are parts generally just much more expensive in the UK than the US? Another example that tells me this may be the case: I need a couple of retaining washers for my Honda walk-behind mowers and whilst in the US they're $0.10 each in the UK they're £1.15 ($1.70 each!). Does anyone know someone in the US who'll ship them cheap to the UK?