CDNDave Posted December 28, 2013 Posted December 28, 2013 Hello everyone, I have a leaking carb. I have read all the posts about the floats sticking etc. So I've already tried the Seafoam route, running it through, draining, and letting it soak overnight, then ride her like stole her etc ... She runs real nice, but unfortunately it's still leaking and only at idle. I've been able to narrow it down to just one of the carbs, and I've taken it apart and cleaned and checked everything I could. The floats seem to move easily, took the float valve out and she's clean. So now I'm wondering what I need to replace? I have a pic and pointed to 2 spots where the fuel is bubbling up from while the bike is running, and only happens at idle. Any ideas? CDNDave Atlanta GA 05 RSV - Ride everyday, all year long!
V7Goose Posted December 28, 2013 Posted December 28, 2013 Everything you say points to a problem with the float valve or float. If it is a leak through the valve, you should see it with just the key on so the pump is pressurizing the line. Possible causes are bad valve seat, bad needle tip, bad o-ring under the seat, terribly high float setting, foreign object stuck in the valve, or a float that does not float. I do not know what that middle arrow is pointing at. Also, you say you see the fuel bubbling in the carb at idle, but you do not say anything about the vent/overflow tube. If that is routed correctly, a stuck/leaking float will cause fuel to run down inside one of the lower front cowlings (the vent is routed near the opening of the air filter. Goose
CDNDave Posted December 28, 2013 Author Posted December 28, 2013 The fuel will spill out the overflow tube that runs down the front cowling. The middle arrow in the pic is looking down inside the carb throat, and it's a needle valve that is connected to a diaphragm. When you throttle these needles pull out and in. So on idle, there is fuel coming out the hole where that needle is in. Is that needle suppose to close that hole? CDNDave Atlanta GA 05 RSV - Ride everyday, all year long!
V7Goose Posted December 28, 2013 Posted December 28, 2013 The fuel will spill out the overflow tube that runs down the front cowling. The middle arrow in the pic is looking down inside the carb throat, and it's a needle valve that is connected to a diaphragm. When you throttle these needles pull out and in. So on idle, there is fuel coming out the hole where that needle is in. Is that needle suppose to close that hole? CDNDave Atlanta GA 05 RSV - Ride everyday, all year long! Actually I was referring to the upper arrow in your picture - stupidly referred to it as the middle arrow since it was pointing to something in the "middle" of the carbs. Sorry. The slide needle is what controls the fuel through the main jet, and no, it dos not actually close it. Goose
CDNDave Posted December 29, 2013 Author Posted December 29, 2013 Ah, that is the nipple for the overflow tube, I left off the tube for testing so I could see the fuel sooner. So no fuels leaks after pressurizing the system, with just the key on. Leaks only when running and in idle. I swapped the float valve with a good one and it still leaks in the same carb, the other carb was fine. I am not sure, but it appeared to be not as much of a leak since the swap. CDNDave Atlanta GA 05 RSV - Ride everyday, all year long!
djh3 Posted December 29, 2013 Posted December 29, 2013 I have not had a pair of these carbs apart. But Like goose said it could be a non-floating float. If you swapped the needle and seat then that would be the next thing shutting of fuel. I dont know what the floats are made of but I have seen the bakolite (or whatever they are) act like a sponge. Its pretty easy to tell if I remember, they feel heavier than what you think is "normal" They should be almost weightless. The old rochecster 4bbl use to be kinda bad about it.
CaptainJoe Posted December 29, 2013 Posted December 29, 2013 (edited) Problem only when idleing? So if you come in from a ride, park and immediately shut off nothing drips ??? A stuck float would allow gas to floweven when IGN turned off... could try bypassing fuel pump and see if it start to drip (indicating bad or dirty needle valve or bad/ improperly set float). still sounds like dirt issue. Assuming(when completly apart) you carb cleaner sprayed all orifices... applie pressurized air to all orifices, properly set float level, assembled ... Not a bad time to change the fuel filter and clean the line out between carbs and filter with a blast of air. The last thing I do before placing back on bike is to turn carb bank upside down and blow into the fuel hose using your mouth. If the floats are working, it will not let air through. If they are sticking it will save you quite a few hours... Perhaps you have a oring missing behind diaprahm?(it will fall out if not careful) 4 screws on side of carb (no need to take carbs off to check) **** EDIT *** Yes i know this is for vintage pontiac but it deals with the dangers of ethanol fuel, take it for what its worth: http://www.highperformancepontiac.com/tech/hppp_0909_ethanol_fuel_and_vintage_vehicles/photo_09.html ***** End Edit **** Edited December 29, 2013 by CaptainJoe
ChrisFrench Posted December 29, 2013 Posted December 29, 2013 I already had this problem, it comes from the O-ring of the valve body http://i56.servimg.com/u/f56/16/46/31/37/m6xfav10.jpg Chris
V7Goose Posted December 29, 2013 Posted December 29, 2013 Problem only when idleing? So if you come in from a ride, park and immediately shut off nothing drips ??? A stuck float would allow gas to floweven when IGN turned off... could try bypassing fuel pump and see if it start to drip (indicating bad or dirty needle valve or bad/ improperly set float). Actually, no - this is not correct. the RSV fuel pump has a positive shutoff in it, so when the key is off, it will NOT leak fuel. But it SHOULD leak with the key on but not started, just from the fuel pump pressure; however, the RSV pump is a very low-pressure design, so you might have to wait a while if the leak is small. But if it really only overflows when the engine is idling, and not when the engine is off and key on, then it seems most likely related to a float valve just barely shutting off and jiggling open from vibration. That would either be caused by a badly misadjusted float, or one that was not fully floating. The fuel pump is going to be putting out the same pressure with the engine running or just the key on, so the only other variable is the vibration. And engine vibration does NOT cause a float valve to leak when the float has normal pressure on the needle. Goose
CaptainJoe Posted December 29, 2013 Posted December 29, 2013 (edited) Actually, no - this is not correct. the RSV fuel pump has a positive shutoff in it, so when the key is off, it will NOT leak fuel. But it SHOULD leak with the key on but not started, just from the fuel pump pressure; however, the RSV pump is a very low-pressure design, so you might have to wait a while if the leak is small. But if it really only overflows when the engine is idling, and not when the engine is off and key on, then it seems most likely related to a float valve just barely shutting off and jiggling open from vibration. That would either be caused by a badly misadjusted float, or one that was not fully floating. The fuel pump is going to be putting out the same pressure with the engine running or just the key on, so the only other variable is the vibration. And engine vibration does NOT cause a float valve to leak when the float has normal pressure on the needle. Goose Yes, I thought of that (not enough pressure/fuel to show up) so I added doing a bypass. Your way is a lot simpler by turning the switch on but not starting... Very good info!.... Edited December 29, 2013 by CaptainJoe
CDNDave Posted December 30, 2013 Author Posted December 30, 2013 Thanks all for the great advice and tips! It turns out to be a badly adjusted float. I went down to Harbor Freight and bought a tool to measure the clearance and the float was .25, I adjusted to the recommended medium of .34 and the leaking stopped. CDNDave Atlanta GA 05 RSV - Ride everyday, all year long!
V7Goose Posted December 30, 2013 Posted December 30, 2013 Very happy you found the problem and got it fixed. Now consider that that carb work would have cost you between $150 and $250 at just about any shop - you got it fixed for free... Maybe membership here is worthwhile? Welcome, and ride safe! Goose
djh3 Posted December 31, 2013 Posted December 31, 2013 thats like 12% of what the shop would have charged. And we are friendly about it. LOL
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