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Motorcycle Forum / General / Sportbikes / September 2005VTR 250 help
Hello all. I'm looking for any help I can get diagnosing this problem... My wife's bike is sick. It will run at WOT, but pours gas out of a tube at the bottome of the frame - fast, not just a drip or a leak. It's like it is being pumped out. The gas that comes out has a very very high volume of oil in it. It is jet black as if you poured gas into a car's oil pan to clean it out. Also, at the tailpipe, it puts out what looks like steam. I traced the tube the gas is being shot from and it goes to a small plastic box under the battery. That box has two large diameter tubes going into it as well. One comes down from the breather, the other comes in from the crankcase. I have no idea what that little plastic box is. Any idea what may be wrong? My guess is something messed up in one of the carbs that is causing it to feed too much gas to one of the cylinders. Any ideas would be helpful. Thanks in advance. >Hello all. I'm looking for any help I can get diagnosing this problem... > [quoted text clipped - 17 lines] > >Thanks in advance. The small plastic box near the battery is the, air cleaner-air box and obviously a carb float is stuck and filling up the air box up with gas. To make matters worse, there is a tube that is used to suck crankcase blowby into the air box as well. What's sounds like is happening is the stuck carb float is pouring gas into the crankcase and it's in turn backing up into the air box (hence the oily gasoline mixture). You could also have gasoline running down the cylinder walls (going the other way "into" the intake of the engine). You can ruin the engine real fast from something simple, like a stuck [1] carburetor float (similar to your toilet floats). Anyway, it's likely happened from sitting and not running too much and is usually easy to fix. You may need to remove to two carbs but if you have a fancy (short or bent) Phillips screwdriver then you can remove the float bowls or occasionally just knocking the butt of a screwdriver head against the float bowl will stop the leak but don't count on it. An any rate, once you fix the problem, change your oil (before running engine again) to prevent any MORE engine damage, as gasoline mixed with oil is a poor lubricant for a four-cycle engine. [1] The float bowl mechanism usually has a pin running the length of the float bowl to act as a pivot for the carburetor float. Carefully remove this pin and the float valve will drop into your hand. Clean and remove any foreign material or better yet buy new "needle and seat" kits from the Kawasaki dealer before starting the procedure. Hope this helps. Bob Nixon, Chandler AZ 01 Sprint ST "RED" 50K miles http://bigrex.net/pictures > The small plastic box near the battery is the, air cleaner-air box and > obviously a carb float is stuck and filling up the air box up with > gas. To make matters worse, there is a tube that is used to suck Air cleaner-air box? What the heck is its purpose? Does it filter the crankcase blow-by before dumping it back into the carbs? Speaking of the carbs, when you take the breather box and look into those little horns under it, there is a black cylinder that can be seen sliding back and forth on (or with?) a needle when the throttle is cracked. What the heck is that? Thanks for the feedback. I was hoping it would just be a carb problem. I think I can tear them down and clean 'em out. >> The small plastic box near the battery is the, air cleaner-air box and >> obviously a carb float is stuck and filling up the air box up with >> gas. To make matters worse, there is a tube that is used to suck > >Air cleaner-air box? What the heck is its purpose? Does it filter the >crankcase blow-by before dumping it back into the carbs? Air boxes act as a Plenum or air holding tank with a stable volume and pressure. As to filtering blowby there is a screen but it's mostly just a convenient place to dump the fumes that get sucked back into the intake and re-combusted. In older designs, four cycle engine crankcase blowby vented out tubes to the street. The EPA didn't let this go on later that around 1977-8. >Speaking of the carbs, when you take the breather box and look into >those little horns under it, there is a black cylinder that can be seen >sliding back and forth on (or with?) a needle when the throttle is >cracked. What the heck is that? That's your CV (constant velocity) carb slides. The needle goes into the main jet for low & medium throttle setting. Wide open, the main jets are nearly unrestricted. Also the needle down the center of the slide is graduated in size to let more fuel in as the throttle is opened. There should also be a vacuum diaphragm that controls the cylindrical slides. This functions as a regulator from your throttle hand to the actual opening of the slides (there should be a throttle plate as well, connected to the throttle cable). IOW, the slides will not open until there is sufficient intake manifold vacuum so that the fuel/air mixture is never too rich or lean. Back in the late 70's, the EPA mandated that motorcycles carbs use the "constant velocity" design. Older carb slides were connected directly to the throttle cable and had no throttle butterfly. Also, newer fuel injection systems use two throttle butterflies (one to your throttle cable and the other controlled by available intake manifold vacuum. >Thanks for the feedback. I was hoping it would just be a carb problem. > I think I can tear them down and clean 'em out. Sounds like a winner. Good luck & let us know what you find. Bob Nixon, Chandler AZ 01 Sprint ST "RED" 50K miles http://bigrex.net/pictures Just to follow up - looks like I won't be having to deal with it. This has turned in to a prime opportunity to talk my wife into an upgrade. So, we'll be getting rid of it and getting her onto a bigger bike. |
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