QuestionQUESTION: well thanks for just reading this i have a 94 kx250 top & bottom rebuilt 6 months ago. the bike ran fine i tried to go for a ride today i started the bike 1/2 kicks it started everytime would run but no band so i brough a new plug changed gear oil cleaned carby (like 10x) still no change the float needle seat alll work fine i removed the bowl hooked the fuel line up held the float up the fuel stoped let it go the and the fuel flows by acccident i figured out if i leave the fuel off it will run with no band fo a minute then it alll comes back until the bowl is empty what's wrong with my bike plz help!
ANSWER: To begin, I would like to thank you for checking all the things you did before asking. It makes my job much easier.
When you run the engine with the fuel turned off the mixture becomes leaner as the bowl empties. Normally, the RPM increases and the power available decreases as the fuel runs out.
If the power becomes more like normal as the fuel runs out it usually indicates that the engine isn't getting enough air. That could be something as simple as a dirty air filter. If you didn't already try it, change or wash your filter as is applicable.
You didn't say where you are, but if it is winter there ice in the air cleaner/filter can also cause symptoms like this. If this is your problem you will find the ice when you wash/replace the filter.M
Mouse nests are fairly common in air cleaners of bikes that aren't used regularly too, but I have seen pics of the air cleaner of a bike that was in regular use that had been filled with nuts by a squirrel too.
A plugged up muffler can make an engine run the same way, but it won't come back as the fuel runs out as much as a blocked air cleaner will.
It is also possible (although less likely) that a jet is blocked in the carb. You say you "cleaned" it, but what do you mean by that? Just spraying some carb cleaner into the intake with the engine running won't thoroughly clean a carb. To properly clean a carb you need to remove it from the engine, open it up and, at very least, spray carb cleaner through every passage, making sure it comes out the other end.
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QUESTION: thank u for your advice Sorry im in Queensland Australia it dont freeze here lol i replaced the filter no diference i tried without the filter still no change but with both if i leave the fuel off it will come back until the bowl runs out off fuel with carb i pulled it out took the bowl off cleaned out the main jet an the little one besideit there is one more which is much more difficult to clean what im doin wrong coil?
AnswerI wondered if you were an Aussie when you called it a "carby". I have some very good friends in Aus. on the CX/GL500/650 forums. They're great folks, but they have no real concept of what cold means. Except for Don who spent some time in Antarctica in his youth. He lost a BSA in a bottomless crevasse there, but that's another story.
It's pretty mild for this time of year here in Ontario, Canada - today's high was about +1c - but one day last week we had a high below -10c. At times like that I wish it didn't freeze here either ;-)
OK, if the power comes back when the mixture leans out the problem isn't compression, ignition or fuel flow. If the air filter doesn't make any difference intake flow can be eliminated too.
I would have a close look at the exhaust next. Maybe take it off and try blowing through it with a compressor. If you can find something that will seal up the space between the pipe and the air gun (maybe a rubber stopper with a hole in it?) that would be best. If you put 100 PSI or so into the pipe and don't get a good blast at the outlet your exhaust is blocked. This happens on dirt bikes and more on 2 strokes, sometimes as a result of dirt/water entering the muffler during a water crossing & messing up the packing and sometimes from soot accumulation (more likely if you use too rich a fuel/oil mixture or if you use motor oil or really cheap 2 stroke oil in the gas).
If that's not it you will have to take the carby off and clean it thoroughly. You might even need to soak it. Besides the jets most carbs have a number of small passages that cary fuel or air to various tiny ports for various purposes such as smoothing the idle or improving off idle power. If it doesn't have a choke butterfly it will have an enricher circuit that, when opened, allows more fuel to enter the mixture for cold starting (the enricher lever is usually still marked choke). Some have accelerator pumps that squirt fuel into the throat when the throttle is opened abruptly. Some have air cut valves to enrich the mixture when the throttle is closed to reduce popping.
The best advice I can give is to take the carb apart as described in your shop manual, blow carb cleaner through every hole there is and follow that with high pressure compressed air. If any of the passages appear to be blocked you may have to soak the carb overnight in either carb cleaner or methanol (AKA Methyl Hydrate - buy it in the paint dept. because it will cost a fraction there of it's price in the automotive dept.) Make sure you remove any rubber parts before you soak it because the cleaner can attack the rubber and make it swell up.
While you are at it, examine all of the rubber bits carefully and replace any that show signs of cracking or have become hard. It might not solve your problem but, at 14 years old, replacing the rubber parts wouldn't hurt.
