Bonneville America Forums Forums Technical Forums General Tech What the heck is going on???

Trash- what is 'the dreaded ecu'?

I reckon anything's possible Ed. I'll give it a shot.

Certainly worth a shot with the manifolds. I'm pretty sure I'm not going to like the answer, but what would a replacement ignitor run if it was the culprit?

Ouch!!

I ran the inline all last year without problem. I also cleaned it recently. Now when I stall there is more fuel in the bowls than before, but not a lot, maybe 1/4-1/3 of a shot glass. And I remeber you metioning the overheating possibility but I figured as cold as the garage has been that may not be it. Tonight I start to backtrack everything I've done to make sure something wasn't missed.

Just for the sake of eliminating things can you bypass the inline filter altogether for a short test?

Did that Ed. With or without the filter I can see fuel flow from the tank to the carb inlet up until the time the bike stalls.

Doug,

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fires right up with the choke. Push in the choke and keeps running 5-10 minutes and dies. Will not start again with or without the choke. Dropped the bowls soon after and there is almost no fuel in them. On the bright side no backfires after tightening everything again. Does it sound like it's starving for fuel? Float and/or needles gummed up? What??

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I’m trying to keep this simple and straight forward. Here goes:


Since your sickle fires up and idles for 5-10 minutes, you are running on the fuel in the bowls.

Clear your mind of all else except the fuel delivery system/components. That is where your pain lies.

Working on the premise that your problem is dry carb bowls, sticking slides have no bearing on trouble shooting fuel supply to the bowls and neither do any of the jets. Header pipes nor air leaks on the manifold side of the carbs don’t have any bearing either. Don’t be barking up the wrong tree. When a sickle runs out of gas it will run lean and exhibit the symptoms you have mentioned. Your bowls being dry are THE reason you run skinny and the engine starves dies. The bowls are the delivery side of fuel to your jets…The bowls allow fuel to feed into tiny orifices. Thus the only component on the carbs that are effected by gravity are each float needle. The float needles are one end of the fuel deliver system problem. The other end is the fuel tap. Look at everything in-between. Like the vent stack for your homes plumbing, your sickle must have an unobstructed vent stack. The tubing between the fuel tap and the carbs must be free and clear. Where the issue to be a clogged fuel tap screen, well, it must be very well clogged. Use an alternate fuel supply, that is, rig up an IV for your carbs. This eliminates the fuel tap clogged issues as mentioned by Greybeard. However, the fuel lines allow fuel to pass OVER TIME.

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With or without the filter I can see fuel flow from the tank to the carb inlet up until the time the bike stalls.

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Of course you do. THIS is the high side of your problem. Greybeard mentioned allowing fuel to drain from your bowls after they run dry (the sickle dies). Having fuel run to the ‘T’ at the carb inlet means you are getting fuel to the ‘T’ only it will not tell you if the fuel line past the ‘T’ is unobstructed. Actually opening up the drain on each bowl will allow you to observe if the fuel is moving past the ‘T’.

Solution: Your problem is a blockage of some sort in the fuel tubing past the ‘T’.

You can send a check to the bonnevilleamerica fund. You’re welcome.

Good points Moe. So we're sort of back to my point from page 3 of this thread, one of the T's is either not allowing fuel into the bowls or the air vent is blocked and keep the pressure from equalizing and not allowing the bowls to fill.
Doug, do this easy test: attach a tubing to the bowl drain and open the drain screw with the petcock open and see if you can drain the tank. Do both sides, one at a time. You'll find the obstruction that way.

Exactly. Something is floating around in the tubing and gets lodged over time. Or gets saturated and swells up over time. A piece of paper towel may have found its way into the fuel line. Don't ask...Or the obstruction allows fuel to pass, but at a greatly reduced rate. Thus when you let your motorsickle sit after it's spring moment(s) the fuel will eventually refill the bowls. If your intent when draining the bowls with the fuel tap on per Ed is too observe fuel flow, then the intention to drain a healthy measure of fuel (the entire tank) will force you to get you past the rush of what fuel is already in the bowls and truly observe if a real fuel flow event is occurring Apparently, you have only been observing the fuel that had already seeped past the blockage.

P.S.: The odds of BOTH float needles sticking are very remote. Has yota been playing with your sickle?

Been saying air/fuel from the start. Even when I mentioned jets I said that wasn't the problem, same with the overheating not causing empty bowls and so on. Thats why I was asking about the filter and now that I know you have been running it and you cleaned it that doesn't seem to be the problem either. So it's seems its to the vent or sticky float/float needle or a partial blockage in the gas line after the clear line. Might run a little gas line anti-freeze through it while the bowl drain is open to eliminate some ice as the possible blockage (don't know how cold it is where your bike is).

I had the benefit of reading everyone's post. But the real problem was the most basic. No fuel in the bowls while a fully laden fuel line is observed after running just long enough to use the fuel in the bowls. And then the bowls refill over time.

Everyone had the right answer, but we all get wrapped up in our understanding of things to the point of not addressing the real problem. This thread screamed the question: Why are the dry float bowls recovering?

True enough, once informed the fuel path was clear I followed the red herring toward the vacuum leak side of things...
Only two reasons for the float bowls not recovering, fuel delivery interuptus or bowl vent blocked.

As did I, I kept thinking tip over valve but with the tank off that wouldn't be the issue. Overheating crossed my mind as I said above too but that doesn't cause empty bowls and so on. So has to be blocked vent or fuel feed. Seems to me it has to be before the carbs if it's the feed since 1 cyl. doesn't cut out , instead it dies all together.

Man you guys are good. I feel like I'm in the middle of an episode of 'CSI'. My next move is to unclog the arteries. I'll post how it comes out.

I've been trying to follow this thread because I am low on carb knowledge and trying to learn a little something, but you guys are way over my head here.

Who wants to spend a weekend taking carbs apart with me?

Having problems Dave, or do you just feel like tinkering? I'm OK to a certain level, but the other guys that posted here are the real gurus. Diagnosing problems remotely is a challenge.

Just future tinkering I guess. I imagine I'll need to get in there some day and I hate paying $80 an hour for things.

The general physics of it I understand, but the specific parts and where they all go I am missing...

anyone know a good primer?

Once you dive in you will see these carbs are not very complicated at all. Might be hard to follow simply because you are unfamiliar with them.

Go to Dinquas page (link in the Tech vault) and read, he has good pictures there and lots of info. It won't make you an experienced mechainc but it will give you a good basic understanding and show where all the bits are.

I would add the Jenks Bolts tuning guide to that list of homework. Pat has a link to the very fine Mikuni carb tuning white paper on his site too. The more you know the more trouble you can get into

Speaking of getting into trouble.....

Anyway, got back into it last night a bit. Pulled the hose from both the vent 'T' and the fuel 'T' and made sure they are clear. As far as clearing the rest of the 'T' components could I safely use a blast of compressed air to try and dislodge any blockage or should I disassemble even further and run something through the pieces? Don't want to cause any more problems. Also, why I'm there is there anything that can be done as preventative maintenance on the float/needles to keep them from sticking? How should I 'unstick' them if this happens in the future?

Suggestion. How I would think about going about it. Get a consensus though as my shade tree is still a sapling.

This picture is for reference only it is not one of our carbs...



The info below was gleaned from the above link.

I wish you would have opened the bowl drains and let a quart or so of fuel flow through. Then closed the drains until the bowls filled up. Walk away for 5 minutes then reopen the drains and let another quart flow through. The idea is have the floats seat the needles. Let the needles be seated for a time, then test fuel flow. This will provide some insight as to the state of the float needles ability to unseat… Anyway, Given that your fuel line is off the 'T' go ahead and
place drain hoses on each float bowl, and position these in a can/jar so to catch the carb cleaner. Open the drains. Insert carburetor cleaner spray can nozzle into the carburetors 'T' fuel inlet port. Spray the Dickens out of that sucker, until pure carb cleaner flows into each container. Reconnect the fuel line and cycle the float bowls with gasoline running at least a quart or half gallon of fuel through the bowls.


Scarier yet, after spraying carb cleaner directly into the float chamber as above, connect a length of fuel line to the carburetor 'T'. Insert the fuel line into the hose of your Wet-or-Dry Shop-Vac. Restrict the vacuum cleaner hose opening with your hand, providing maximum pressure differential to the fuel line and let 'er roar! After a minute or so, restore machine to operational configuration and see if everything is all better (don't forget closing the drain screws!).
"WARNING: DON'T EVEN THINK ABOUT USING A VACUUM CLEANER AROUND YOUR SICKLE IF THERE IS THE SLIGHTEST POSSIBILITY OF ELECTRIC-SPARK IGNITION OF FLAMMABLES. CHECK YOUR VACUUM CLEANER MANUAL."


This should clean out the fuel lines. Look at the collection cans to see what if any garbage came out. The whole point of cleaning out the fuel line is to open them up. You have not tested the restricted flow theory yet. I would do that first. I would think you could open the drains on the bowls (with the catch cans in place) and blow some compressed air into the 'T'. Low pressure at first just to see if you can feel any air coming out of the bowl drains. One at a time too, then both at the same time. This will help you determine blockage restrictions and would be performed in place of the fuel flow test. You stated that the fuel line from pingel to 'T' is full of fuel when the bowls are dry. I take it you have a clear piece of fuel line there? Yes and an in-line fuel filter. Solid fuel on both sides of the inline filter? Anyway, hope this helps.

Again, I am guessing that you have blockage/restriction of some kind between the T and the bowls. Do the flow test. Than you will know.

To keep the float needles from sticking replace them. You cannot recondition the seals. I know the odds of both float needles sticking are remote but both of them sticking would cause your bowls to be dry. (No fuel past the needles) And would also explain the bowls Fuel recovery over time.

Thanks Moe.

And thanks Ed.

Finally getting to the float valves - good - although I can't figure why both would be stuck??

Blackdog....have you opened the drains and let a quart flow out of each carb. If you can get that much to flow quickly, your fuel flow is ok. If not fix the blockage between the float valves and the petcock as already been stated.

I wouldn't blow compressed air in the fuel inlet to the carbs unless the float valves were removed or unless you could keep the pressure very low. Make sure the drains are opened.

My last 2 rides ended up with me on the side of the road, crack the gas cap and in sucks air... that valve in the vent line mounted on the frame between the carbs was stuck... Such a silly little thing can sure blow ya day...

Hold everything! Opened up the carbs yet again this morning. Cleaned everything around the slides and needles topside. Dropped the bowls, floats and needles underneath and gave a good cleaning also. Shot more carb cleaner and air thru the fuel intake. Float needles looked good as new but I switched sides on them just to see if it made any difference as to which bowl would end up empty. Reassembled and fired up. Started watching the clock after dechoking. 5, 10, 15 minutes passed no problem. What the heck, let her go. It's about 35 degress in the garage so I ran a full 30 minutes before I shut down. Never a sputter or hesitation. Probably too early to break into show tunes but I could be cured. I must have hit the right thing or combination of things on my latest trip through the carbs.

Thanks to all that posted suggestions. I can't tell you how much I appreciate everyone hanging in there with me on this. Although I've never had the pleasure to meet any of you in person you are considered as brothers. Hopefully someday our paths will cross and I'll have the opportunity to pick up the tab.

Oldroadie,

Hopefully this isn't a hijack. I see regular references to the problems with gas cap venting. Is this a problem with all years and models, I have an '07 Speedy. More to the point, is the easiest preventive solution a vented cap from one of our trusted vendors? Thanks.

Glad to hear things are running well. I imagine whatever was floating in the system got the boot when you pulled everything off and flushed with carb cleaner and air.

If I have a vented cap, can I just put a squirrel condom on the tank vent tube underneath and let it go? That long tube is one more thing to be in the way.

yep, as long as the tank can vent.Don't over fill the tank then though, I imagine the vent tube doubles as an overflow in the event of over fill and heat expansion.