Author Topic: Vapor Lock? - can't be. (Read 9188 times)

Deltarider · « **Reply #25 on:** January 16, 2009, 07:26:08 AM »

With the original fuelfilter as above there is absolutely NO point having extra inline fuelfilters.

tygrant · « **Reply #26 on:** January 16, 2009, 07:26:42 AM »

goon that makes sense but whats the pop he is hearing when he hits it with air? thats what made me think stuck float, slapping back down. he said he cant get it started till he does that. i would think that if the air locking was the problem after a short period of time fuel would have made its way back down?

mystic_1 · « **Reply #27 on:** January 16, 2009, 07:33:41 AM »

The original post states than when the fuel line is not attached to the carbs, fuel flows normally, so I think he's eliminated everything above the fuel line.

mystic_1

Brian G · « **Reply #28 on:** January 16, 2009, 08:51:49 AM »

Now its getting good!

Quote

when the fuel line is not attached to the carbs, fuel flows normally,

But the first post says

Quote

Suddenly there is no more fuel in the line which I have now run along side the tank to observe the fuel flow.

How can that be if the fuel flow is normal?

If the line is empty of fuel, it is full of air. Is the air coming from the tank side? Or the carbs? Floats stuck open wouldn't admit air (carbs would overflow); neither would floats stuck closed (no air could enter).

+1 on the air lock in the inline filter. I had exactly the same thing happen on my 550K. Took the filter out, replaced it with a straight (inclined downwards) run of tubing and she ran like a dream.

Good luck!

goon 1492 · « **Reply #29 on:** January 16, 2009, 09:28:26 AM »

Well that's true Tygrant, I should have added that to the post above that on top of the float valve sticking maybe theirs a air lock situation too.

A combo of the two....With their powers combined we have SUPER HEADACHE!

couldn't help myself with the captain planet humor.....

mystic_1 · « **Reply #30 on:** January 16, 2009, 10:07:47 AM »

Good question. Symptoms are a bit contradictory.

Quote from: mycb750k6 on January 15, 2009, 04:40:55 AM

Suddenly there is no more fuel in the line

Which sounds like a problem in the flow coming out of the tank...

Quote from: mycb750k6 on January 15, 2009, 04:40:55 AM

When I pull the line from the tank, fuel flows readily from the tank but when I re-attach to the carbs - no flow.

Which sounds like a float or venting problem.

Quote from: mycb750k6 on January 15, 2009, 04:40:55 AM

From that point I can re-connect the fuel and all is well - until it happens again.

Problem is intermittent, to add insult to injury

Quote from: mycb750k6 on January 15, 2009, 04:40:55 AM

If I take an air compressor and blow in the line that goes to the carbs I hear and feel a small bop as if something is being blown back into place.

Which sounds like stuck floats, but let's confirm something, mycb75k6, are you saying that you're blowing air into the carbs or into the tank here?

mystic_1

mycb750k6 · « **Reply #31 on:** January 16, 2009, 12:07:08 PM »

OK let me see if I can be more specific because often I'm not clear and leave chunks out.

1. My engine is running fine and then starts to run out of gas. At this point I verify the float bowls are now empty, the fuel line is empty and the engine dies from no fuel. At this point no fuel will flow in the line.
2. I have the fuel line running along the outside of my carbs with an inline filter so I can see the fuel flow and easily access either the tank side or carb side fuel tubing.
3. If I pull the tank side tubing off the filter, the fuel flows from the tank into a waste container.
4. If I reconnect that line to the filter, no fuel will flow. It's jammed up.
5. If I turn off the gas at the tank and pull the carb side tubing from the inline filter and blow compressed air into it and into the carbs, I hear the pop from one of the bowls.
6. If I then connect the carb side tubing to the inline filter and turn the fuel back on from the tank, the fuel flows normally and the engine is happy again - for a while.

Now the picture of the petcock in this post is exactly like mine. I have taken it out and cleaned it. What is that stuff, cheesecloth?

When I said the fuel flows normally, I meant until the point where something prevents further fuel flow, like a float valve, air in line, or something. From that point no fuel flows until I do the compressor thing. But like I said, disconnecting the line from the inline filter that comes from the tank and fuel flows out. Putting it back on the filter and it does not - until I pop it.

tygrant · « **Reply #32 on:** January 16, 2009, 12:57:15 PM »

i would run a straight line from the tank to the carbs and get rid of that inline filter, if your tank is clean, free of rust and you have the filter on the pet cock you dont need it. then i would clean the carbs and put it back together and see how it goes. that will fix the problem.good luck and let us know

goon 1492 · « **Reply #33 on:** January 16, 2009, 01:33:09 PM »

well I like others would like to see you try this without the inline filter, believe me that is what caused the same thing to my bike literally. It had just enough air in the line that caused the fuel to barely trickle and that wasn't enough to fill the bowls while the engine is running.
Now to get back to the popping sound that could even be the sound you would hear when you get a float bowl that is full of fuel which would cause a closed valve and when air pressure is applied you are literally forcing enough air pressure into the lines that its causing the float valve to "pop" open and let air in even though its trying to stay closed. In theory it sounds right but it would make me think that it should or would in turn cause a little fuel to spit out the drain/vent line from the bowl being full of fuel.
Don't fret bro we will figure this gremlin out and exorcise the demons!

mkramer1121 · « **Reply #34 on:** January 16, 2009, 01:41:23 PM »

I also don't see where you said you checked the vent in the gas cap. I had a very similar problem when I got my 550 and fuel would flow freely when I removed the line at the tank but not with it attached. Same problems you are having and it did turn out to be the clogged vent in the gas cap (switched caps and voila). When it stops flowing, open your gas cap and shake the tank, see if you can get the air bubbles to flow back up from the carbs and through the open gas cap hole. If it works, then you know where your problem lies.

mycb750k6 · « **Reply #35 on:** January 16, 2009, 01:44:17 PM »

goon,

I will remove the filter as soon as I've Pro-15 the tank and get my new petcock which will make everything tankside spiffy clean which I planned on starting today. But I must say I had this problem before putting the filter inline and really I'm just using it as a connector for easy fuel line removal.

You made me think of something when you mentioned the popping overflowing the bowl drain line. What actually happens when the popping occurs is that fuel drips rather readily from the air filter area and I haven't researched what that means yet but yet another clue.

mkramer1121 · « **Reply #36 on:** January 16, 2009, 01:47:19 PM »

Quote from: mycb750k6 on January 16, 2009, 01:44:17 PM

goon,

I will remove the filter as soon as I've Pro-15 the tank and get my new petcock which will make everything tankside spiffy clean which I planned on starting today. But I must say I had this problem before putting the filter inline and really I'm just using it as a connector for easy fuel line removal.

You made me think of something when you mentioned the popping overflowing the bowl drain line. What actually happens when the popping occurs is that fuel drips rather readily from the air filter area and I haven't researched what that means yet but yet another clue.

Your floats are set incorrectly and your drain tubes are clogged, causing the bowl to overflow and dump into the airfliter.

KingCustomCycles.com · « **Reply #37 on:** January 16, 2009, 01:48:50 PM »

Fuel from the air filter box area is a plugged overflow drain tube or a huge excess of fuel overcoming the capacity of the drain. Either way, it is too much fuel in the bowl.

tygrant · « **Reply #38 on:** January 16, 2009, 07:52:00 PM »

GROW A PAIR and take those carbs off!!!!

haha take those carbs off and clean them, its easy , just open your seat take off the airbox, loosen the screws on the rubber boots, pop the cable throttle cable off and the things will fall into your hands! it sounds to me like the posibility of sticky floats and cloged over flows means you need and carb DOUCHE!!!!

CALL ME tomorow. im puttering around on my bike all day. seriously if u have a quick question and dont want to post and wait for a reply my cell is 603 608 7914 names Tyler be glad to help. by the way, since you had this problem before you had the in line filter its got be the carbs. Good luck!

HondaMan · « **Reply #39 on:** January 16, 2009, 08:57:22 PM »

Quote from: mycb750k6 on January 15, 2009, 04:40:55 AM

My 76 CB750 K has developed an annoying way of running out of gas. Suddenly there is no more fuel in the line which I have now run along side the tank to observe the fuel flow. When I pull the line from the tank, fuel flows readily from the tank but when I re-attach to the carbs - no flow. If I take an air compressor and blow in the line that goes to the carbs I hear and feel a small bop as if something is being blown back into place. From that point I can re-connect the fuel and all is well - until it happens again. ANYBOBY know whhat that pop could be and how I could service it? Float bowls? Gullys clogged?

BTW, fuel system is clean, carb bowls are clean, main jet cleaned.

It just behaves as a vopor lock that I can't get rid of until I blow through the line with compressed air and get that pop again. Oh yeah, I put a inline throw away filter in the line to prevent any outside influence.

What in the world is it?

Have you recently replaced the fuel lines, and perhaps routed them down below the carbs, then back up?

Reason I ask: in the last 2 months I've seen a K6 and an F1 where this was done, and both run out of gas after a few minutes. Rerouting the fuel line to come out ot fhte petcock, thru the bracket to the first tap, then across the top of the back of the carbs to the second tap, seems to solve it nicely.

Spanner 1 · « **Reply #40 on:** January 16, 2009, 09:54:50 PM »

Post#2..respectfully suggest air lock, no carb. tear-down necessary...gas-tank must vent for fuel flow....I know fuel flows out when you pull the line off the petcock..but the vacuum is released at this moment..my 2 cents..open gas cap, no vac. on tank for sure.

mkramer1121 · « **Reply #41 on:** January 16, 2009, 10:52:19 PM »

Quote from: Spanner 1 on January 16, 2009, 09:54:50 PM

Post#2..respectfully suggest air lock, no carb. tear-down necessary...gas-tank must vent for fuel flow....I know fuel flows out when you pull the line off the petcock..but the vacuum is released at this moment..my 2 cents..open gas cap, no vac. on tank for sure.

person # 3 to suggest the easy fix (like me!), lets see if he listens....

mycb750k6 · « **Reply #42 on:** January 17, 2009, 08:06:57 AM »

Tyler,
I'll call this morning on your cell.

With respect to the cap, I had verified the breather hole was clear, installed a new rubber gasket and tried this procedure with the gas cap open just to eliminate that aspect of the problem. I'd done this a couple of days ago with no change.

I'm surprised to read the system is so sensitive to the fuel line routing. There isn't a lot of room under there in the first place and none for a filter effectively.

Also I'm surprised to hear I should remove the inline filter which I'll do once the tank is por-15'd. There's no debris getting through but I don't want to add another unknown at this point by letting any foreign matter get to the carbs.

Seriously I've tried all the above suggestions because I appreciate you guys help.

With respect to the air filter having gas dripping from it, I had supposed that blowing the compressed air to the carbs had blown the fuel everywhere for that carb in addition to giving me the pop. Speaking of that, is my filter element now ruined?

HondaMan · « **Reply #43 on:** January 17, 2009, 08:47:59 AM »

Quote from: mycb750k6 on January 16, 2009, 12:07:08 PM

OK let me see if I can be more specific because often I'm not clear and leave chunks out.

1. My engine is running fine and then starts to run out of gas. At this point I verify the float bowls are now empty, the fuel line is empty and the engine dies from no fuel. At this point no fuel will flow in the line.
2. I have the fuel line running along the outside of my carbs with an inline filter so I can see the fuel flow and easily access either the tank side or carb side fuel tubing.
3. If I pull the tank side tubing off the filter, the fuel flows from the tank into a waste container.
4. If I reconnect that line to the filter, no fuel will flow. It's jammed up.
5. If I turn off the gas at the tank and pull the carb side tubing from the inline filter and blow compressed air into it and into the carbs, I hear the pop from one of the bowls.
6. If I then connect the carb side tubing to the inline filter and turn the fuel back on from the tank, the fuel flows normally and the engine is happy again - for a while.

Now the picture of the petcock in this post is exactly like mine. I have taken it out and cleaned it. What is that stuff, cheesecloth?

When I said the fuel flows normally, I meant until the point where something prevents further fuel flow, like a float valve, air in line, or something. From that point no fuel flows until I do the compressor thing. But like I said, disconnecting the line from the inline filter that comes from the tank and fuel flows out. Putting it back on the filter and it does not - until I pop it.

This picture tells the story: the fuel line is incorrectly routed. Remove the filter, run new rubber lines. Go down and back, through the carb mount (there's a hole for it there), tee into the first carb. Then continue on to the other pair. The fuel line must be ABOVE the carbs to let the fuel drain into them: it won't go back up the tube very well because there is no "fuel pressure" in a simple fuel drain system like these. There is no need for a fuel filter: there is one in the petcock.

rklystron · « **Reply #44 on:** January 17, 2009, 09:20:05 AM »

Good catch Hondaman.

mycb750k6 · « **Reply #45 on:** January 18, 2009, 09:46:49 AM »

I just Pro-15'd my tank so I'll have to postpone my research on this until 96 hours have pasted but I'll come back to this next week. Thanks again.

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Author Topic: Vapor Lock? - can't be. (Read 9188 times)

KingCustomCycles.com