Hej
Vad jag vet så är det inget vanligt fel.Ta och kolla den här länken.
http://faq.f650.com/FAQs/HardStartingPoorRunningFAQ.htm
http://faq.f650.com/FAQs/EngineNewFAQ.htm#Strange%20Engine%20Noises
Å sen lite till jag hittade i en annan faq
"Bad Valve causing Starting Problems?
My wife has been struggling with "Cold Starts" on her F650 and we tried just about everything on the website. This Spring we took into the dealer and felt the problem was the Fuel Enrichener (aka choke) or carb. They cleaned both....no luck the problem still existed and we took it back in. 2 weeks ago we got a call from the dealer. They did a "bleed -down" test on the cylinder and it did not meet specifications, indicating something bad with the valves. They did a quick look and thought an exhaust valve looked burned. A week later they did remove the head and confirmed that 1 exhaust valve was burned and it need to be replaced, which would resolve the starting problem. My 1st question...why would a bad valve cause a cold-starting problem? Well I was educated. The enrichener (choke) is not mechanical but vacuum operated. With the bad valve the engine might not be creating enough vacuum to allow the choke to work properly. Well I wasn't sure but said lets give it a go! This week the mechanic called. Said the bike was back together and started easy, ran fine, and seemed to gain a little power. The good news was that BMW decided to warranty the parts, valves, gaskets etc. That saved a couple hundred. I asked why a bad valve at 15,000 miles. Most likely a bad batch of soft valves in the new bike. Last night week picked the bike up, it started fine, ran good, my wife says it did feel a little "umph". Its only been one day but we are encouraged. I would have never guessed a valve causing this kind of problem might help others. Bob & Mary Beth Alexander (she's not a chain ganger yet but soon) PS Judson Cycle in the Mankato, Minnesota area has been great in helping on this one!
As far as the vacuum thing affecting starting, it's not directly choke related. Almost all choke/enrichener methods (except direct fuel injection) need manifold vacuum to work. Suck nothing into the cylinder, enrichener or choke or fuel mix doesn't matter, no fuel mix to fire. And a burnt valve not sealing affects both the engine vacuum and compression. If it's badly burnt there's no vacuum to suck in the fuel/air mix.
Of course you most notice the compression/vacuum problem WHEN THE ENGINE WON'T START! After that, if it will fire a few times, even a few misfires, sometimes the heat/detonation/pressure will be enough to get the valve to seat well enough to run. After that, you don't notice the problem again UNTIL THE ENGINE WON'T START!
In a multi cylinder engine, you can last a long time with a burnt valve, as the other cylinders still run. Can't fake it with a single! So the problem was really that there was a burnt valve affecting engine compression/vacuum, preventing it from starting, not really that the burnt valve affected the choke/enrichener function. And that point could be in the Hard Starting FAQ's. So also could "out of gas", "missing spark plug" and "broken crankshaft".
![Smile :-)](./images/smilies/icon_smile.gif)
HsN.
Hard Starting / Power Loss After Shim Change?
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//FÅ