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Jetting (I think) question for a 2004 KTM 250 EXC RFS

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Hello,

I just bought a used 2004 250 RFS. I only rode it around in the yard a couple of times before I installed a Recluse Z start, so I can't say whether it was doing this before I installed the clutch or not. I truly believe that it has nothing to do with the clutch, because it works perfectly for the first 15 or 20 minutes of riding. My problem is - after a quick warm up the bike runs perfectly for about 15 or 20 minutes. After that, it stalls out everytime right after starting from a dead stop. I have to use the clutch lever to build up revs to get the bike to move or it will just keep stalling. Once it starts this it continues until quit riding. It is getting very frustrating. I know how to work on carbs as far as changing out jets and needles and I actually have a JD kit on the way, but I would really like someone to explain to what the problem is. Like I said, I bought the bike used and I have no idea what jets are in it or where the fuel screw is set or anything like that. Any help would be appreciated. Please post questions if I left out any info that would be useful in diagnosing the problem. Also, the bike has 35 hours on it.

Thanks

Jim

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The JD kit is going to help, my Son rides one of these and we collaborated with James on the 250 kit. However you have more wrong than that, they are very ridable stock.

first thing I would do is take the bike outside, park it over a pan, on the left side of the carb bowl there is a small allen head screw, turn the gas on, remove that screw and whatch the gas drain, let it run several miniutes and monitor the flow, if it slows after a few miniutes loosten the gas cap while listening, If you hear a "woosh" and the flow of gas increases you have a vent problem in the gas cap or vent hose. Many riders have removed a ball that is inside the gas cap. I can describe how it works without having one in front of me but its intent is to stop gas from coming out when the bike is on its side, occasionally it takes its job too seriously and does not allow air in to displace gas as it runs out.

Next tilt the carb to the right, remove ht e big plug on the bottom (17mm?) then forward of the main jet is the pilot jet. You will need a small screw driver to get it out, remove it, do not hold it to your lips, just blow very lightly at it to clear any gas, then hold it up to the light;

If you see fuzzy light you have water in the gas.

If you see clear crisp round light your problems are elsewhere.

If you don't see light, now hold it to your lips and blow hard, if that does not clear it soak it in lacquer thinner, or wait for your kit, I beleive it will have one 1 size larger than you have now?

If it is water toss an once of rubbing alcohol into the gas and it will pass thru.

If it was plugged solid and a lacquer thinner fixes it then it must have st too long and the gas evaporated.

To run and start good they must idle good!

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Thanks for the advice. I opened up that vent on the left side of the carb and it flowed like a champ. I went ahead and checked out the carb as well. It had a 160 main, 45 pilot and the fuel/air screw was set at 1 turn out. I thought the pilot might be pattially blocked so I cleaned it and reinstalled. I put the bike back together and rode about 10 minutes before it started doing the same thing again. If anyone else has an opinion, I truly would appreciate it. Right now, I have a 4500.00 bike that I can't ride and it is killing me. James Dean or anyone than can help _ HELP.

Thanks

Jim

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Jim

So when you flowed gas out the drain you let it continue to flow for more than 10 miniutes?

It is unrelated to the problem you are experiancing but those 250's need a 175 main jet, which will not matter until you get this other problem sorted out.

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Hello Dave,

I truly appreciate you taking the time to try to help me figure this out. To answer you question, no I did not let it flow that long. I backed the screw out to where it was flowing at its fastest (actually I went too far and gas started coming out the screw hole, but I screwed in back in some to where it flowed full speed) for only 2 or 3 minutes. The flow never changed so I took the gas cap off and it still did not change so I went on to the jets. You sound like you know what you are talking about, so I will try whatever you reccomend.

Thanks again

Jim

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If the tank vent is not flowing air in it will flow gas out for a while, such as the 10 miniutes you experianced before it stops do to a vacume, how long it will flow will vary based upon the gas/air ratio in the tank, how much the plastic tank will colapse etc. KTM has had quite a few with gas caps that do not allow any air in.

Another problem (not the one you have today) comes up with those check valves that we sometimes put in the vent hose, designed to stop gas from flowing out when we are upside down, sometimes they get installed backwards? Sometimes they stick. On occasion even when installed corrrect if you start out with a full tank the gas rid in slow technical stuff where there is little wind and lots of heat generated the gas in the tank swells up from heat and floods the carb.

If I had my druthers we would all have free flowing vents. Indusrty manufactorors have Attorneys that all talkabout stuff like the letter from the Attn of some guy that laid under his bike while it burns, then they go tell manufactoring that they are going to put in a check valve, then we get to figure it out when they quit working!

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I was never concerned about the vent tubes spilling fuel until I filled a CR in my garage to the top. The cap sealed an air pocket in the tank that eventually warmed up and started to push fuel out the overflow. The fuel ran down the steering head tube and down the back of the fender. It was disconcerting to see fuel dripping onto the floor of the garage when I came into the garage.

Jim,

Try the jetting kit settings and see how they perform. If the problem continues, recheck the fuel flow with a full tank and with the gas cap tight. Check the float level and electrical connections. Replace the spark plug if it looks dark.

Thanks,

James

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Jim, I heard part of the story in the industry about 25 years ago, think it happened on Mercer Island, guy was burned bad, sued Honda big time!

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