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Old 09-29-2013, 09:11 AM   #16
SOLO LOBO
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Start by pulling a fuel line and blowing through it into the tank to see if the screens are blocked (or partially blocked)
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Old 09-29-2013, 10:27 AM   #17
Stan_R80/7
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A couple of basic tests I would try:

1. Remove the float bowl on the right (problem) side. Place a pan under the carburetor to catch any gasoline. Turn on both fuel petcocks. Look for fuel coming out of the float valve (from the bottom of the carburetor). If no fuel flows, then there is a blockage in the cross over line and/or line to the carburetor or the needle valve has crud upstream.

If test 1 fails, then test 2 would be done.

2. Disconnect the fuel line to the right carburetor. Get a container (i.e. an empty coffee can, jar for recycle bin, etc). Position container so fuel can flow to the container. Turn on petcock(s) and time how long it takes the container to fill. The slowest acceptable rate would be 8 oz (250 ml) per minute.

If test 2 and test 1 failed (no fuel or inadequate fuel flowed) then I would replace the fuel lines. Good luck!
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Old 09-29-2013, 12:39 PM   #18
BalefireX OP
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First of all guys, thanks for all your suggestions and insights. I did a few more tests today and I don't know if I'm any closer to a solution...

All tests done with full tank of gas, bike on center stand:

1. With petcocks off overnight, removed float bowls. Left (good) side: 2/3 full, Right (bad) side: 1/4 full
Visually inspected the float hinge and needle assembly, both seemed to move freely up and down, neither side had a small wire clip anywhere other than the hinge.
NB: these are Bing /9 and /10 carbs.

2. Replaced one float bowl at a time and measured 1 minute of flow from each carb. Left side: ~375ml/min, Right side: ~300ml/min.
Right side test was repeated with both petcocks on (as the first test only used the petcock on the side of the carb being tested), this returned ~375ml/min.

3. Replaced both float bowls, started bike, ran for 1 minute just above idle. Turned off bike, shut off petcocks, removed float bowls. Left side: 2/3 full, Right side, 1/2 full.

4. Replaced both float bowls, started bike, ran for 1 minute at 4000 rpm. Turned off bike, shut off petcocks, removed float bowls. Left side : 2/3 full, Right side, 1/3 full.

So... it seems to me like there is fuel getting to both carbs, the crossover is working, and with both petcocks open flow shouldn't a problem. Fuel lines are new so that shouldn't be the issue either. I'm starting to think more and more that it might be internal to the carb, but I can't figure out what.
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Old 09-29-2013, 12:55 PM   #19
Big Bamboo
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I would start by adjusting the float height on the carb that is missing. Fuel flow should stop when you raise the float to the point that the floats molding line is parallel with the bottom of the carb. 1/4 full float bowl is too low...
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Old 09-29-2013, 02:15 PM   #20
disston
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The right side is either not getting enough fuel pressure because of debris obstructing the lines, filters, screens or inlet. Or the floats are not adjusted correctly.

If you turn the petcocks off and remove the bowls the side you remove first will have a higher level because the gasoline in the lines will flow to that side. You should fill the bowls, remove fuel lines at the carbs then remove bowls. The small amount in the brass nipple won't matter but there is a bit of gas in the 2.5 feet of hose on the system.

If done correctly both bowls should be about 2/3 or 3/4 full.
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Old 09-29-2013, 03:34 PM   #21
Plaka
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Quote:
Originally Posted by BalefireX View Post
First of all guys, thanks for all your suggestions and insights. I did a few more tests today and I don't know if I'm any closer to a solution...

All tests done with full tank of gas, bike on center stand:

1. With petcocks off overnight, removed float bowls. Left (good) side: 2/3 full, Right (bad) side: 1/4 full
Visually inspected the float hinge and needle assembly, both seemed to move freely up and down, neither side had a small wire clip anywhere other than the hinge.
NB: these are Bing /9 and /10 carbs.

2. Replaced one float bowl at a time and measured 1 minute of flow from each carb. Left side: ~375ml/min, Right side: ~300ml/min.
Right side test was repeated with both petcocks on (as the first test only used the petcock on the side of the carb being tested), this returned ~375ml/min.

3. Replaced both float bowls, started bike, ran for 1 minute just above idle. Turned off bike, shut off petcocks, removed float bowls. Left side: 2/3 full, Right side, 1/2 full.

4. Replaced both float bowls, started bike, ran for 1 minute at 4000 rpm. Turned off bike, shut off petcocks, removed float bowls. Left side : 2/3 full, Right side, 1/3 full.

So... it seems to me like there is fuel getting to both carbs, the crossover is working, and with both petcocks open flow shouldn't a problem. Fuel lines are new so that shouldn't be the issue either. I'm starting to think more and more that it might be internal to the carb, but I can't figure out what.
Hmmm First off, I would mark your bowls. See my build thread here. Couple of ways to adjust floats but the bottom line is the height of the fuel in the bowl. This method addresses that directly. if a float isn't floating as much, it won't matter. The fuel height is the fuel height. period. I got fancy with a couple tiny pits made with a dental burr in the dremel. Any mark will work. The sharpie splotch is just to give me something to scribe a line in with my calipers. I was surprised it took gas. Haven't looked recently but it will work short term it seems.


If the level in the bowl is low either enough gas isn't getting in or more is being used. A LOT more. this would be a massive carb misadjustment. Not likely. So I'd go with it not getting in for the moment.

Adjust the floats for correct fuel height per your mark. Don't worry about what's in the lines. Give the bowls a full minute or more to fill to account for a flow issue if there is one. You are just after float adjustment for the moment.

Unless the fuel lines are less than a year old, replace them. Basically you want to remove the line from the crossover to the carb and examine it as well as the fuel inlet at the carb to the bowl. You should be able to look through the line. But for the effort of getting that line off, may as well put a fresh one back. And for that, do them all. 3' of 1/4 fuel line from the auto parts store works. Cheap. Put a nice stainless washer on the petcock nipple ahead of the line. 1/4" will be tight. Makes it easy to get off. Also clean the screen in the petcock nipple while you are there.

if you have never used 1/4" the experience is valuable. You might want the looser cloth braided next time. I generally replace lines every other year. They get hard.

Putting hardened lines back risks a ling chip of rubber getting in the line from the lip as it is pushed on. This will be downstream of your filter. bad.

You might do a fuel flow test from each petcock, at the petcock, no line, on both main and reserve. Tank full. Flow data on Snowbums site.You're looks for "same-both-sides" for the moment. This isn't your problem but check. if the flow is low order two petcock to tank gaskets. Any time the petccocks come off the tank, replace these unless they are very new. Re-used old ones weep and your petcocks get all varnished up and crummy looking. leave the petcocks on the tank until those come in.

With the new lines on do a flow check at the end of the line where it connects to the carb. Then replace the fuel filters and repeat. If no difference put the old filters back on. Spray some (very little!) carb cleaner through the new ones and put them on the shelf to wait their time.


The float valve is simple. The inlet pipe goes to a passage that ends in a very small hole. Below that hole is a larger bore and the float needle rides up and down in this bore. The float needle (hardly a needle, it's a chubby little thing) has a conical rubber tip. When it's all the way up in its bore the tip plugs the little hole from below. The float pivots on a rod and a little tab pushes the float needle up it's bore. you bend that tab very slightly to adjust the position of the float so that it has the needle all the way up and plugging the hole when the fuel level is just right.

read Snowbum on this adjustment.

if you do a flow test from the carb do not have the bowl in place. Have fuel flow for a measured time into a clean jar or something and see how much you get per unit time. Check and compare both sides.

If the lines are new and clear, the float needle is descending and you have weak flow into your jar, then I would say there is bit of crud blocking the tiny hole in the top of the float needle bore. There could also be crud in the bore. The needle is triangular so the fuel can flow around it.

Remove the carb. remove the float needle pivot pin. Must do this in the correct rirection. The knurled end does NOT get pushed through the supports trashing the bores. You push from the smooth end so the knurl comes out the other side first. The float then lifts away along with needle which is attached by it's clip wire. Shoot some carb cleaner up through that little hole to clear it. If you spray so what comes out the inlet pipe goes onto a fresh paper towel, you might spot the villian. Examine the tip of the float needle. A ridge in the conical tip suggests replacement. not having a rubber tip really suggest replacement. if there is a ball in the tab end, poke it with a very small screwdriver. It should be spring loaded. Replacing it is obvious. Dealing with the little clip is an untold joy. No beers before this operation. Unfortunately the needles are costly. if the carb hasn't been leaking, leave it alone. You know how to do it anytime now.

The classic problem is the needle tip gets worn or hardened, or there is a bit of crud on the needle side, or the needle won't go up it's bore because it doesn't feel like it or has a headache or whatever, or the float sticks on the pivot rod...whatever...but the float needle doesn't seal the hole and the carb overflows on your boot---or the parking lot. Thus you always turn the petcock off when your boot isn't handy to soak up the spilled gas.
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Old 09-29-2013, 04:16 PM   #22
Warin
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Your measured fuel flow rates are ok .. .3l/min = 18l an hour .. ok.

The low fuel level on the right side is suspicious .. the fact that it varies is even more suspicious...

What is the fuel level in the right side carby .. just let it sit for a while motor not running. If this level is 'normal' then I'd suspect a blockage just before the float needle.. The blockage is disturbed from time to time by the actions of the needle bumping up and down .. thus a variable flow rate..
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Old 09-29-2013, 06:04 PM   #23
r60man
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I am thinking that you are wasting your time with the fuel solution. Check all of your connections on the Starter relay under the tank. I had a situation very similar to this that was driving me nuts. Finally I accidentally knocked the starter relay and it started running on both cylinders, then died. I tried cleaning all of the connections, but eventually I wound up replacing the relay and it has run perfectly since then. Give it a shot, at this point it is only a few minutes and you really have nothing to lose.
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Old 09-30-2013, 11:31 AM   #24
BalefireX OP
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More work and more strange results...

Today I took apart the problem side carb, removed the float and the float needle (there was a frantic 10 minutes when I dropped it and lost the little ball bearing in the parking lot) and sprayed carb cleaner up through where the needle was. A clean paper towel on the fuel inlet revealed a little bit of gunk was blown out...


I blasted the rest of the carb with carb cleaner while it was apart and then wiped it down and reassembled everything. Fuel flow to the right side seemed improved so I took it for a ride.

It rode well for the first mile but then started to stutter again and I had to ride it back on one cylinder.

At this point I decided to try the starter relay and removed the tank, labeled the relay, and cleaned all of the contacts before replacing everything. Started it up again and it was running on both cylinders, so I went for another ride.

This time it ran great for quite a while, including getting up to highway speeds. It stuttered once or twice during a 10 mile trip between at 45 and 70mph but recovered quickly.

I turned around and rode it home without issue until I got into stop and go 20mph traffic. It went from idling normally to idling at approx 2k rpm and then cutting out. By the time I made it home about 1/2 a mile later, it was again running on one cylinder.

It seems so strange that the issue would be intermittent like this, but I am hoping that all this detail might point one of you guys in the right direction.
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Old 09-30-2013, 12:33 PM   #25
Big Bamboo
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The ball bearing in the float needle should NOT fall out ! Get a new float needle, or two, for starters.... Did you adjust the float level ? Also, squirting UP through the jet orifice only pushes gunk up where it can come down and cause more problems. Try pulling the fuel line to the carb and spraying down through it, with the jet needle out of the way, of course.
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Old 09-30-2013, 07:22 PM   #26
r60man
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Quote:
Originally Posted by BalefireX View Post
More work and more strange results...


At this point I decided to try the starter relay and removed the tank, labeled the relay, and cleaned all of the contacts before replacing everything. Started it up again and it was running on both cylinders, so I went for another ride.

This time it ran great for quite a while, including getting up to highway speeds. It stuttered once or twice during a 10 mile trip between at 45 and 70mph but recovered quickly.

I turned around and rode it home without issue until I got into stop and go 20mph traffic. It went from idling normally to idling at approx 2k rpm and then cutting out. By the time I made it home about 1/2 a mile later, it was again running on one cylinder.

It seems so strange that the issue would be intermittent like this, but I am hoping that all this detail might point one of you guys in the right direction.
I am thinking that this should tell you something. Starter relays can be pricey. There is a way to use a GM starter relay, and it is probably in the dark secrets thread. My starter relay had gotten doused with brake fluid when the master cylinder blew up. I had thought that I had cleaned it all off when I fixed the master cylinder but it had worked its way in. Interestingly mine would idle perfect and then not run on both cylinders when traveling at speed. Good luck.
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Old 09-30-2013, 07:26 PM   #27
disston
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I think he had the carb off when he blew the carb cleaner thru the inlet.

Yes to new float needles. There is also a small spring under the ball. Did that fall out also?

Not sure from that photo but is the tip of that needle rubber or solid metal?
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Old 09-30-2013, 09:01 PM   #28
BalefireX OP
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Yes, the carb was off when I blew the carb cleaner through it.

The ball and spring didn't so much as fall out as were knocked out when I clumsily dropped the float needle from carb-height onto asphalt. I put it back in and it seemed to be okay? The tip of the needle is solid metal.

I admit I don't exactly follow how the starter relay could/should affect running on one side... does someone with a better understanding of the electrical system want to clue me in here?
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Old 09-30-2013, 11:52 PM   #29
Plaka
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Quote:
Originally Posted by BalefireX View Post
Yes, the carb was off when I blew the carb cleaner through it.

The ball and spring didn't so much as fall out as were knocked out when I clumsily dropped the float needle from carb-height onto asphalt. I put it back in and it seemed to be okay? The tip of the needle is solid metal.

I admit I don't exactly follow how the starter relay could/should affect running on one side... does someone with a better understanding of the electrical system want to clue me in here?
The ball is spring loaded in the needle.

The old metal tipped needles should be replaced. But it if isn't leaking, whatever. They are not cheap and you know how to do it anytime.

Clean up the bosy of the needle. Fuel has to be able to flow around it and it must move freely in it's bore.

Finding an empty carb bowl when one side isn't running points to a fuel issue.

The starter relay won't affect running on one side only. The main electrical feed stops by there and drops off some power to the relay. That connection can b flaky and affect power to the whole bike.

Sorting a one side only ignition issue is quite simple. get the fuel feed to both carbs right first, then power balance them.

You anywhere near Canojoharie?

BTW, for parking lot work, score an old white pillowcase from the thrift store for a buck. Spread this under the working area to catch dropped bits. You can also lie on it, put stuff in it, etc. handy item to have, good size and they don't unravel.

Plaka screwed with this post 10-01-2013 at 12:22 AM
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Old 09-30-2013, 11:54 PM   #30
disston
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Did you ever take the petcocks off and clean them and the gas tank out?
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