Author Topic: All carbs leaking out airbox side orifices (Read 2789 times)

pscycle927 · « **on:** March 10, 2013, 05:31:32 PM »

Well I'm running out of patience with this 77 CB750k I took the carbs off and cleaned them I thought I did a good job ...Wroooonnnggg I forgot to clean the accelerator pump so I look in the back airbox off no squirt I pull the carbs clean Accelerator pump passages and both balls clear out holes in Diaphragm everything looks good ready to rock and roll got good squirt in all 4 carbs. Wrooonnngg I put the carbs back on and hook up fuel line start to tighten them down and fuel starts flowing out the airbox side of the # 4 carb. I think the hole on the left. Hmmm I pull them off again remove bowls spray everything out double check my float height looks good put carbs back on turn on fuel no leak begin to tighten the #3 carb guess what shes wizzen out the #4 still I've had these pups off and on more times than I care tell I had no leak until I cleaned the accelerator pump but I never even pulled the bowl off #4 just the one with the a pump Any thoughts? I'm about to start selling parts these things are touchy.

DJ_AX · « **Reply #1 on:** March 10, 2013, 10:00:43 PM »

heh heh... it's kind of an initiation thing I think... you have to show the bike you really do care.

Yeah they are a bit touchy but once you get 'em dialed in .... mmmmmm hmmmmmmm

I haven't really had to fiddle much with my carbs for years ...
yeah .. but only after running in circles like you are now...

and welcome to the forum...

iron_worker · « **Reply #2 on:** March 11, 2013, 11:56:07 AM »

Did you inspect or replace your float needles and seats? If they are corroded or have any amount of debris they won't shut off the fuel even if your float height is set correctly.

Also if it's coming out your overflows you can check that your stand pipe in the fuel bowls is cracked. You will have to look very closely as they are pretty small.

IW

mrrch · « **Reply #3 on:** March 12, 2013, 06:17:54 AM »

I rig up a remote fuel source so I can test them with gas on my work bench before installing on the bike (saves some grief installing & removing numerous times)

pscycle927 · « **Reply #4 on:** March 12, 2013, 12:51:09 PM »

My fuel leakage is coming from the orifices on the airbox side of the carbs not out the overflow tube the two holes side by side I did not have this problem until I cleaned the accelerator pump and orifices then it started leaking I can see a very small leak in #1 as well but #4 gushes pretty good I removed the bowl and manualy lifted the float on #4 and saw no fuel coming out of the float needle jet. I reamed out the diaphram hole that went to the accelerator pump when I cleaned it someone said it was supposed to have two holes is this the problem? the hole going to the bottom of the accelerator pump did not have a hole that I could see at first I assumed it was plugged so I reamed it out to match the other hole size Is this for air only and now I have fuel feeding back throught the reamed hole?. The ball was stuck in the bottom of the accelerator pump It is now freed up. I put new float needles in two carbs beacause the little spring bobber was stuck on two of them but like I mentioned the float needle doesnt leak when manualy lifting the float.

pscycle927 · « **Reply #5 on:** March 12, 2013, 01:28:01 PM »

Now all four carbs leak from airbox side orifices what is going on ? what is the proper name for these two holes please and I feel it has to be that diapfram can someone please confirm if both these holes are supposed to be open in acceleartor pump diaphram. Thanks for the replies. if the little check ball in the accelerator pump cover is not perfectly round will fuel backflow? This is supposed to be a checkvalve correct? how can I test this?

pscycle927 · « **Reply #6 on:** March 12, 2013, 02:55:50 PM »

Ok Im convinced that the checkvalve on the accelerator pump cover is the problem the ball was corroded a little and I tried cleaning it with very fine grit sandpaprer but i dont think it is a perfect circle anylonger allowing fuel to bypass the ball does this sound plausible? I dont find just the ball anywhere should I replace the whole cover? everthing else seems good. Anyone have a ball? I wonder if I tore apart a birdshot shell if it would match lol.

flybox1 · « **Reply #7 on:** March 12, 2013, 03:51:54 PM »

did you get the check valve back together properly with the spring in the middle?
check with member sohcdigger. he might have the pump bowl with a working check valve..

flybox1 · « **Reply #8 on:** March 12, 2013, 03:55:28 PM »

Quote from: mrrch on March 12, 2013, 06:17:54 AM

I rig up a remote fuel source so I can test them with gas on my work bench before installing on the bike (saves some grief installing & removing numerous times)

+100
even just a small funnel attached to a spare fuel line connected to the carbs, and a pint of gas on the table to get your bowls filled....

pscycle927 · « **Reply #9 on:** March 12, 2013, 04:57:57 PM »

I have my tank setting on top of toolbox and carbs set level on third drawer with rag under them thanks for the tip I was tired of removing them from the bike I dont think the acceleartor pump checkball is the problem I removed it and it seems to be working properly I am loosing my mo fo with these carbs this is not making any sense.

flybox1 · « **Reply #10 on:** March 12, 2013, 05:01:04 PM »

so, when you turn the fuel on, it still leaks out the intake side?
you need to remove the float bowls on the leakers and verify your float valves are doing their jobs...

pscycle927 · « **Reply #11 on:** March 12, 2013, 05:17:17 PM »

Correct it still leaks with fuel on I have removed them all double checked the float height and manualy lifted floats to see if it stll ran out it did not still flow when lifted.

flybox1 · « **Reply #12 on:** March 12, 2013, 05:25:17 PM »

ensure the flat portion of the floats is at the same level as the flat tops of the pilot jets.(14.5mm)
fuel would leak out the overflow tubes at the bottoms of the carbs if the float valves were not working.
look for obstruction somewhere else...like the connections between carbs. dry it really well and try to pinpoint where it is leaking...

pscycle927 · « **Reply #13 on:** March 12, 2013, 05:49:41 PM »

They are leaking out the high speed and low speed circuit holes on the airbox side of the carbs. heavy flow not just a trickle more so from #1 and #4 but all seem to leak. when bowls are empty after removing them as they fill back up I hear air bubbles gurgling then they fill and flow out H/S l/S circuit holes.

CoachDoc · « **Reply #14 on:** March 12, 2013, 05:54:22 PM »

Have you checked the floats themselves to see if they leaked and have partially filled with gas?

Vinhead1957 · « **Reply #15 on:** March 12, 2013, 06:01:14 PM »

Are the floats brass?

pscycle927 · « **Reply #16 on:** March 12, 2013, 06:43:52 PM »

I have checked the floats they are not brass they do not leak floats all run level with the jet with carbs sitting on an angle so they just nicely set on the float needle valve Ive torn them apart swithced things around rechecked everything and keep having the same problem they fill up and pour out the high speed and low speed orifices. The carbs look great nothing is out of order looking at them they were not super dirty but the accelerator pump was not working one of the holes was plugged on the diaphram after I got everything clean in the accelerator pump I had this leak situation so I figured it must have something to do with the accelerator pump but it all seems to be ok. I cannot figure these things out.

scottly · « **Reply #17 on:** March 12, 2013, 06:47:29 PM »

Check the levels in the bowls with the clear tube method. If the mechanical float setting appears correct, but the fuel level is too high, check the little spring loaded plunger in the float needle; I've seen a couple on K7 carbs that had almost no spring tension at all, allowing those two carbs to piss gas.

pscycle927 · « **Reply #18 on:** March 12, 2013, 07:23:01 PM »

When I initially cleaned the carbs I noticed two float needles that did not spring so I replaced them and put carbs back together No leaks I started bike it ran decent but bogged when I cracked throttle hard I noticed I had no fuel coming out accelerator pump nozzles so I took carbs off again squirted carb cleaner into accelerator pump holes it took a bit of squirting but they did free up and squirted proper I also dissembled pump on carb and found only one hole on diaphram micky mouse ears I reamed out the other hole and made sure check valves were working properly. I put carbs together now when I turn on fuel petcock carbs fill and keep flowing out the high speed and low speed circuit orifices even on the carbs i didnt replace float needle jet. Also I removed the bowl and manually lifted float and flow did stop. I noticed the carb specifications manual on this site recommends 12.5 height everyone seems to say 14.5 on the forums or level with the low speed jet my next move Is probably lowering the float height a bit I'm at a loss here.

750K · « **Reply #19 on:** March 12, 2013, 10:29:22 PM »

I had the same thing happen with my 77 pd carbs, I cleaned the float needle seats, replaced all four float needles, adjusted the float levels, made sure the floats themselves weren't hanging up on the carb bodies or bowls and still had the overflow out of the passage ways. It drove me nuts!!!, one carb would overflow one minute then not the next. I swapped needles and floats from a carb that wasnt leaking into a leaky carb trying to track the problem but that didnt do squat, one try it would be one carb. After re adjusting or swapping in new needles three carbs would leak, it was all over the place. The root of the problem ended up being the tab on the float that you bend to adjust the float height, the needle had worn a small dimple in the tab and wasn't allowing the needle to seat stopping the flow of gas.

Check the tab metal tab on the float, if there's a dimple worn into it lightly file it off and polish it with some fine sand paper or a dremel. It's a process of elimination but the float itself was the only thing I had'nt replaced with new parts, carbs were cleaned new jets, float needles, o-rings and gaskets all around.

Here's the link to the thread when mine was leaking
http://forums.sohc4.net/index.php?topic=113321.0

pscycle927 · « **Reply #20 on:** March 13, 2013, 08:17:11 AM »

I did see your post and I looked for grooves and saw none this bike only has 14500 miles on it everything internaly looks great the tank is spotless on the inside last night I removed the bowls and saw a few little black specs in there like I said the tank is spotless so Im thinking I may have a rotting fuel line I dont know how else I would get the little specs so Im going to look into that further today that could very well be the problem I sure hope it is. I dont really understand why this would all of a sudden become an issue but I guess I have wrenched that hose around while cleaning the carbs plus spraying carb cleaner through while it was on the carbs may have pushed things along.

flybox1 · « **Reply #21 on:** March 13, 2013, 11:04:44 AM »

question: Did you connect the fuel line to the carb fuel overflow vent n!pple?
It IS right next to the fuel inlet.

Tugboat · « **Reply #22 on:** March 13, 2013, 11:12:02 AM »

Did you lose the little o-ring that goes on the #2 bowl acc pump?

pscycle927 · « **Reply #23 on:** March 13, 2013, 10:42:16 PM »

No fly my carbs dont have that vent and tug nope its there. I didnt get a chance to work on it today Ill dig in tomarrow hopefully. Thanks fellas.

harisuluv · « **Reply #24 on:** March 14, 2013, 12:56:44 PM »

Those carbs do all still have 4 individual vents. There are four holes in the same place as the nipples are on the other PD models. It is quite tiny and pretty easy to get clogged..

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Author Topic: All carbs leaking out airbox side orifices (Read 2789 times)