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Old 22 Oct 2006
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Unhappy ktm lc4 power loss!!!!!!!!!!!!!

i did about 400ml during the weekendwith the bike(2003 ktm 640 adventure) and i think that i gradualy lost power.
I say "i think" coss i only realised it on the last 200ml.
it battled to reach 70ml/h.i checked the valves and there is nothing wrong with them. after checking the valves i took the bike for a test run up a hill and then suddenly lost a lot off power and can't reach 50ml/h.the exhaust noice is also deeper than normal. the bike starts easy and idles normal.

anybody got an idea what it could be?I am at a lost since and have had the bike for only about 3 months now.bought it second hand and have replaced the inlet and outlet camfollowers.

any info would be appreciated
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Old 23 Oct 2006
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Suggest you try advrider.com at the thumpers forum, u will get a response there!
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Old 23 Oct 2006
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It's only a wild guess and probably wrong, but if the exhaust charectaristics have changed, eg baffle gone internally and is blocking the system, then that would cause power loss/exhaust note change, same goes for inlet rubbers on the carb etc. a thorough inlet/outlet check may help.
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The most effective way of turning petrol into noise without the side-effect of horsepower
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Old 24 Oct 2006
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www.thumpertalk.com may have some suggestions on fixing the problem.
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Old 25 Oct 2006
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Red face

thanks for the info sofar.Have allready posted on the websites.
Most of the replies think that their is someting wrong with the carberator.
i'll let you guys know as soon as i found the problem!
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Old 25 Oct 2006
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You didn't mention where you were riding, so if it is not in the UK, then low octane fuel could be the problem.

Assumedly if you did 400 miles, then you must have filled up your tank halfway through the ride? Did the power loss become noticeable after filling up the tank? If so, maybe it was dodgy fuel?

If you have a 2003 model, then the CDI should be switchable for low octane fuel. You could try switching the CDI to see if it runs better (assuming you still have the same tank of gas). There is a post in this section that shows how to disconnect the CDI switch for low octane (<95).

good luck
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Old 26 Oct 2006
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Difficult to diagnose when not there.

You say you replaced the cam followers which implies the carb remained in place.

But, if you have removed the carb, are your sure the clamps connecting it to the inlet are properly tightened? I forgot once and had similar problems. Is it difficult to start the bike?

This doesn't sound like electrics as usually they either work or not and in my experience the ignition circuit isn't usually a problem on later LC4s.

I doubt it's an exhaust problem - what can go wrong unless it's a blockage as mentioned by Joe?

You haven't left any rags inside the exhaust? Did this myself once as well.

If the above fails then maybe a carb stripdown and clean is in order. Is the needle OK?

Air filter good and clean?

Vacuum feed from the inlet manifold to the fuel pump OK?

Fuel pump: have you tried filling the tank (i.e. fuel level above the carb) and bypassing the fuel pump?

Sorry to be pessimistic, but one other possibility is a cracked piston, but I doubt this as your 03 should have a forged piston.

Good luck.
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Old 26 Oct 2006
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sounds like a strange fault, best of luck sorting it.
you say the exhaust note changed, the snorkel hasnt come out of the air box making it lean, and this is the change in noise you noticed. whats the plug colour like, lean or rich
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