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Discussion Starter · #1 ·
I have a 2001 Honda Shadow Spirit VT750DC. It's acting like a Kawasaki...
I'm having a fuel issue that I can't seem to figure out let alone fix. The motor runs excellent at idle for about 5 minutes but the begins to sputter and pop then quit running. After waiting for a time period it will start and do the same thing. The engine seems to be starving for fuel. I checked the fuel pump and turned on the ignition but the pump did not pump fuel. I removed the bowls from the carbs to discover they both had a white powdery residue that some research suggested that i may have gotten some fuel contaminated with water. As a result I cleaned the tank with acetone followed with alcohol to remove any residual moisture. I cleaned the carbs with Gunk Cleaner and carb and choke cleaner also using compressed air. I have in the past done the same thing with good sucess. The spark plugs NKG Standard plugs were all carbon fouled. They were replaced with Iridium plugs and new NGK RACING Plug wires. I replaced the fuel with fresh fuel along with a K&N fuel filter. I rode the bike for a short trip (65 miles) one afternoon without incident. The next time I went to ride the same symptoms returned. I find it hard to believe the problems are in the carbs. All internal parts of the carbs were replaced. I tried the fuel pump and it did not pump fuel eventhough it had adequate fuel and 12VDC power to the pump. As a result I replaced the fuel pump. With no success. I tried every experiment I could conceive to correct the problem. I replaced the petcock valve. Tonight I disconnected the fuel pump from the circuit and directly wired the pump to an external battery and the pump worked flawlessly. I rechecked the power at the connector and their was 12 VDC. I plugged the pump back up and again the same symptoms reappeared. I disconnected the plug and using a test light determined there was 12VDC but when I plugged the pump back up then i had no power at the plug. I repeated the test that confirmed power but upon plugging the circuit together the same thing happened. Can ANYONE TELL ME WHATS WRONG????? I'M AT MY WHITS END. Any help would be greatly appreciated.
Best Regards,
Charlie
 
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Let me sleep on it, Baby baby Let me sleep on it ;)

I ain`t a carb man, but we DO got some who frequent these pages @CAMKMM040596

Thinking fuel pump oR cloged carb though,
Dennis

We`ll be in Ashburn selling Chicken plates Saturday Charlie come visit
 

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The normal fuel pump operation is that one coil signal will go to the fuel pump relay and signals that the engine is running. So when you turn the key on the pump may pump a couple of seconds then shut off until the engine runs and the signal goes to the relay.
It is a safety feature to keep from a fire if the bike falls over and the key is on.
When it dies, loosen the carb bowl drain screws to see if 1 or 2 ounces of fuel runs out.
If it does then the carbs have enough fuel and it is more an ignition problem.
 
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Discussion Starter · #4 ·
Swifty,
I forgot to add that the fuel pump relay had been REPLACED TOO.
Charlie
 
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Do the fuel in bowls check when it falters, and maybe it will show it is not a fuel supply problem at all.
It can be a ICU ignition problem from the unit heating up.
Or the pulse generator changing as it heats up.
Are the plugs still getting fouled? Maybe a restricted air supply ? Is the air intake all factory stock?
 

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Runs for a bit, then dies as if starved for fuel. Can start again after sitting for a bit. Replaced everything in the fuel system but still does it.

Have you checked the tank vent?

Clogged tank vent causes the tank to develop vacuum, eventually cutting off fuel supply, as there needs to be air coming into the tank to allow fuel to flow out. Bike sits for a while and air makes it's warm into the tank, pressure equals out allowing fuel to flow again, and bike can be started again.

Easy way to check is to run the bike until it does, and then immediately open the gas cap. If you hear a big rush of air or a pop like a soda can, tank vent is your culprit.
 

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I`m hoping you get this issue resolved Charlie...
I knew our Gurus would be on top of it with the cure/suggestions...

Praying with you,
Dennis

Did I mention our Saturday Chicken-Que in Ashburn???
All our Georgia, Florida, Alabama folks > come eat lunch with us
 

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I'm going to repeat what was mentioned in this order. This is tail chasing and if you don't follow the first order of business, there I said it.
1. Set valves.
2. Check compression.
3. Key on, listen for the pump to run and shut off.
4. Capture both fuel levels of each carb. They should measure close to equal.
5. You didn't screw the drain screws tight yet.
6. Key on, you should hear the pump, you should see both drain hole begin to flow.
7. Should have added full tank after the comp test.

Up to this point, the full tank filled to the neck shows if the vent cap stops the flow that fast with the least amount of air in the tank. So you are killing all the birds in the fuel loop. From clogged gas cap, to kinked/collapsed hose, to fuel pump out to drain holes, then it's not the fuel delivery up to this point.

Choke and spray is not clean carb assembly. I have no clue what new carb parts are, but if white powder was found, might be in the carb body itself, not the [alleged] new jet parts. NAPA carb dip and redo a thorough 20-25 minutes of soaking. Wash with water, air blow dry, or now use the evap type spray cleaners if no air. Every hole you can find. No rubber dipping or it will swell. Orings between carbs when not broken down won't be affected to much to worry about.

Leave the air screw in on the dip. If never drilled out, still, not going to hurt the cleaning process.

Easy way to check is to run the bike until it does, and then immediately open the gas cap. If you hear a big rush of air or a pop like a soda can, tank vent is your culprit.
Disagree. Shook down a bike just yesterday. Tank cap blew off when I went to fill it to the neck. If I had a vent problem, I'd never get to the end of the block. That's why I topped it off at the neck. Ran for over a 115 mile loop. Sure was not the soda pop cap.
 

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Discussion Starter · #9 ·
The normal fuel pump operation is that one coil signal will go to the fuel pump relay and signals that the engine is running. So when you turn the key on the pump may pump a couple of seconds then shut off until the engine runs and the signal goes to the relay.
It is a safety feature to keep from a fire if the bike falls over and the key is on.
When it dies, loosen the carb bowl drain screws to see if 1 or 2 ounces of fuel runs out.
If it does then the carbs have enough fuel and it is more an ignition problem.
Captain D & Swifty,
Sorry its taken so long to respond but wanted to wait so I could give a good report. Well it's a mixed bag. I retested everything again and found the same results during the tests that were suggested by all responders. Some test go without saying like plug wires (new), fuel (adequate and clean), even took off the tank and cleaned it with acetone, dried out with compressed air, then followed with alcohol 90% Isopropoyl to disperse any water, then dried with compressed air. The tank air vent was checked and blown out and found to be clear and working. As I said there is no problem I can think of with the carbs that were cleaned and new parts replaced inside. Compression and combustion and ignition is occurring or the engine would not run to begin with. Still feeling it is a fuel problem I checked the bowl drains that indicated what I already knew there was probably less than 2ml of fuel in there when drained. I went back over the petcock (new), fuel filter (new), fuel line (new) and found fuel was flowing through this part to the fuel pump. Tried pump (new) and replaced with a refunded new pump and found it to not be pumping. I unplugged the pump and found that the circuit had 12VDC coming to it. I had replaced the fuel relay switch before these problems came up after initially replacing the fuel pump. I scratched my head and the test meter had been left connected to the relay circuit. I kept pondering your statement about the relay circuit and it just seemed to keep sticking in my mind. Just sitting there I plugged the fuel pump back into the circuit and a funny thing happened. There was no power to the pump. It dawned on me that the relay was not sending power to the pump. THAT HAD TO BE IT!!! I removed the pump from the circuit and supplied it with 12VDC and it pumped its little buns off. Shocked a POed I went and got the old relay switch and hooked the pump and fuel lines back up. The engine stated running rough and popping for about a second then click it went to running like a new bike. I took it on two separate road test on two days of approximately 20 miles. The bike performed flawlessly. Then yesterday me and the wife went to town and just before leaving the bike started to act like it wanted to skip and pop but would not do like before only mildly. When I got on the parkway I drove it like I stole it and when I arrived home it seems to be running OK. WHAT GIVES???? Any more suggestions. I want to go to the mountains this summer but I can't put it on the road if its not dependable.
PUZZLED
Charlie
 
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Grasping at straws > when I suggest looking at those diaphragms, BUT I think you did that when you had the carb off?
 

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Those are electronic relays. The relay triggers off the yellow-blue wire from the ignition coil. Their sole purpose is to STOP the pump if the motor dies. long as the icu sees the pulse from the ignition pickup, it grounds the yellow-blue wire to fire the coils and the pump runs. technically you'd probably see a low ac voltage with varying frequency on the yellow-blue wire WHEN it's running if you looked at it with a scope while running.

If it does it again, bypass the relay for testing purposes by jumpering the black to black-blue at the relay harness plug, bypassing the relay. It will run fine like that, just be aware that if you crash the fuel pump will still be pumping... turn your key off asap. Might also check the connector pins along the wires in the fuel pump and coil circuits to the icu and the icu connector for clean pins and a good ground.
 

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Discussion Starter · #12 ·
Those are electronic relays. The relay triggers off the yellow-blue wire from the ignition coil. Their sole purpose is to STOP the pump if the motor dies. long as the icu sees the pulse from the ignition pickup, it grounds the yellow-blue wire to fire the coils and the pump runs. technically you'd probably see a low ac voltage with varying frequency on the yellow-blue wire WHEN it's running if you looked at it with a scope while running.

If it does it again, bypass the relay for testing purposes by jumpering the black to black-blue at the relay harness plug, bypassing the relay. It will run fine like that, just be aware that if you crash the fuel pump will still be pumping... turn your key off asap. Might also check the connector pins along the wires in the fuel pump and coil circuits to the icu and the icu connector for clean pins and a good ground.
Old Guy,
I have a couple of questions so I can understand everything, while I am intelligent I am not the sharpest knife in the drawer and by no means a qualified motorcycle mechanic. would it be possible that the yellow/blue wire may be going bad and would replacing the wire be a possibility? This wire I assume runs from the lower coil pack (rear Cylinder) to the ICU? Is the ICU the box that rests on top of the battery in a tray? Next question involves air/fuel. The needle valves are covered by caps and are no adjustments. I read about removing the caps which I successfully completed when rebuilding the carbs, Adjustment doesn't seem to make any noticeable difference I can hear. As a result I turned the needles in to seat and then backed them out 2 1/2 turns. The engine starts quickly and runs well at idle. Since the last incident it has not popped, backfired or all those crazy noises but it does not seem to run smoothly. I rode it to the store yesterday and fishing with the same performance. I was sitting still and revved the engine a couple of times and while at idle I could detect a slight black smoke and a slight smell of gasoline as though the engine is running too rich. Could the problem be that the carbs need adjusting and if so how do I do it. I can't hear a difference at idle while adjusting the screws. Do I need to turn them out a 1/2 round and see if it smooths out or can you tell me how to do it?
Charlie
 

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Discussion Starter · #13 ·
Grasping at straws > when I suggest looking at those diaphragms, BUT I think you did that when you had the carb off?
Hello Cap,
You are correct. I did replace the diaphragms with the ones that came with the carb rebuild kit. I messaged Old Guy and if you read it let me know your thoughts? Hope you and Ann are fine. Maybe if I get this matter resolved we can ride. I lost my contacts in my phone this week so I can't call.
Charlie
 
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That is the ICU on top of the battery. The wire itself runs from the relay to the coil, then to the ICU i believe. regardless, there are 3 connections on it. may not be bad, But could be. unhook both ends and at the coil, clamp the meter leads on each end however you can and ohm it while wiggling the wire along the path, see if it changes from (ideally) 0 ohms. Could be frayed, some broken strands, or corrosion on the connectors causing high resistance. Also look at all the pins on the ICU connector and the ICU pins for oxidation/corrosion. Verify the ground wire for the ICU has a good connection.

Or the relay is bad, more than one person has gotten a bad one brand new. It's an electronic part. it's either good or bad, the quantity on hand nor the age have anything to do with it. (You have no idea how many "lessons" it took for me to learn that.) I jumpered mine more than 5 years ago, I'm still testing...

2-1/2 to 3 turns should be OK for a stock/mostly stock bike. I'd double-check the choke cable routing, one could be hung up and not closing off the enrichment port. Took me 3 tries to get them routed correctly the 1st time I pulled my 750 Ace carbs. And once again, verify the float bowl vent and tank vent are both clear. Either can cause intermittent flooding and the tank vent can also cause fuel starvation if the tank vacuum fights the (possibly intermittent?) fuel pump and wins. That can depend on outside temps at the time. Sometimes the fuel vapor pressure when running can counteract the tank vacuum and act normal.

going to be offline for a few days... will check back when I can
 

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Discussion Starter · #15 ·
That is the ICU on top of the battery. The wire itself runs from the relay to the coil, then to the ICU i believe. regardless, there are 3 connections on it. may not be bad, But could be. unhook both ends and at the coil, clamp the meter leads on each end however you can and ohm it while wiggling the wire along the path, see if it changes from (ideally) 0 ohms. Could be frayed, some broken strands, or corrosion on the connectors causing high resistance. Also look at all the pins on the ICU connector and the ICU pins for oxidation/corrosion. Verify the ground wire for the ICU has a good connection.

Or the relay is bad, more than one person has gotten a bad one brand new. It's an electronic part. it's either good or bad, the quantity on hand nor the age have anything to do with it. (You have no idea how many "lessons" it took for me to learn that.) I jumpered mine more than 5 years ago, I'm still testing...

2-1/2 to 3 turns should be OK for a stock/mostly stock bike. I'd double-check the choke cable routing, one could be hung up and not closing off the enrichment port. Took me 3 tries to get them routed correctly the 1st time I pulled my 750 Ace carbs. And once again, verify the float bowl vent and tank vent are both clear. Either can cause intermittent flooding and the tank vent can also cause fuel starvation if the tank vacuum fights the (possibly intermittent?) fuel pump and wins. That can depend on outside temps at the time. Sometimes the fuel vapor pressure when running can counteract the tank vacuum and act normal.

going to be offline for a few days... will check back when I can
Old Guy,
Thanks so much for the advice and I will check the choke cables. I assume they need to be greased so I will try to grease them. The routing is a problem and I am unsure if mine is routed correctly. Since you will be gone I will try to find the correct routing example online. I took my bike up to my cousin's shop this afternoon as he has a friend that works on bikes some and I have been told he would be able to fix it. Then again you know how that is?.?.? While there I thought I would give it a try to adjust the air fuel screws and like in the past it seemed to get worse. I can smell fuel so I know that it is not being burned. I tried settings of the screws anywhere between almost seated to 1 turn to 1 1/2 to 2 to 2 1/2 with little success. I can't wrap my head around a rich mixture when the fuel filter is sucked almost dry with the fuel pump intermittently pumping fuel in spurts that seem to be unable to keep up with the demand. The pump when I straight wired it as you suggested does not continuously pump. Then when you wire it directly to an external motorcycle battery it pumps continuously. My fuel filter is a K&N clear filter tube and you can see the flow of the fuel and it is erratic to say the least. I am puzzled by the behavior of this bike not to mention frustrated. It just seems like I can get one step ahead to wind up two steps back. You may be onto something about the choke cables so I will check these out. My gas cap is a locking cap that is removed with the key but I am unsure if there is any way to disassemble and clean it but it doesn't seem to not be venting even though I don't know how it works. I will continue to try to fix it though as I don't give up easily and I don't accept defeat. There is a way to figure this mess out and fix it, it's just I haven't figured it out yet. Will continue with your suggestions and update you. Will let you know if I get it fixed and what the problem was. Thanks for the advice. BTW my cousin had some electrical cleaner and sprayed the connector on the ICU but I will definitely go back over everything myself and check all the things you have mentioned.
Charlie
 

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The choke cables are actually opening an enrichment valve, when open they richen the fuel mixture approx 10%, could explain the screws not affecting it much.

The fuel pump is a pulse type , has an internal pressure switch and should only run when the float needle is open. Turning the key on with it jumpered black to black-blue in the harness plug should cause the pump to run for a couple seconds if the fuel level is low in the bowls, fast clicking, then slow and stop in a couple seconds as the float needle seats. there is a test in the shop manual where you jumper the pump, route the fuel hose into a container, then turn the key on for a set amount of seconds, pump should pump a certain minimum amount into your container to be considered good. check the shop manuals.
 

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I don’t think the gas cap is a venting type on these bikes. There is a tube in the tank that starts at the highest point of the tank. It is then routed out of the tank (right rear of the tank on my bike) where a rubber hose is attached and the hose is routed to below the bike.

If you have not done so I would suggest making sure the hose and tube are clear.

Eric


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Discussion Starter · #19 ·
The choke cables are actually opening an enrichment valve, when open they richen the fuel mixture approx 10%, could explain the screws not affecting it much.

The fuel pump is a pulse type , has an internal pressure switch and should only run when the float needle is open. Turning the key on with it jumpered black to black-blue in the harness plug should cause the pump to run for a couple seconds if the fuel level is low in the bowls, fast clicking, then slow and stop in a couple seconds as the float needle seats. there is a test in the shop manual where you jumper the pump, route the fuel hose into a container, then turn the key on for a set amount of seconds, pump should pump a certain minimum amount into your container to be considered good. check the shop manuals.
Old Guy, et al (latin for and others),
I spent the whole day working on my bike. I watched it go from worst to first and anything in between but I am still puzzled somewhat by it. I did jump the wire on the relay with a short cut paper clip that I taped over to prevent a possible shortage. The pump now works exactly as you described so now there is no fuel issues or is there???? The choke cable seemed to be tight and in a bind with one plunger looking a little ****ed somewhat. I removed the assembly gave it a good shot of PB Blaster followed by lube. After some old sailor habits mainly cursing I managed to reroute the assembly to where it seems to work fine now. When the engine is running all you have to do is choke it a little and it will immediately die, so now I know that is fixed. along with the fuel issues or maybe not??? The friend of my cousin I spoke of dropped by and listened to the engine after being briefed on the symptoms. His response was the engine was skipping especially from the front cylinder. He had another appointment but suggested removing the carbs and check the jets making sure it is clean. I did and I noticed the white residue in the front carb. Not bad but none the less present. I cleaned every hole and orifice again on both carbs and reassembled them. Then reinstalled them with the usual tact of a sailor and a few more off the wall comments. I also think I'm going to find another place to buy fuel as this is the 2nd time I have found bad fuel. During all my labor everything was checked and rechecked including vents and etc. All checked out so I adjusted the air/fuel screws per the shop repair manual 2 3/8 + 1/8 = 2 1/2. I experimented with 3 turns out but it seemed to run better at 2 1/2. The engine does not skip anymore and seems to run very well. But occasionally I can detect a pop if I slam down on the throttle. If I am slow with the throttle up everything seems perfect. which is inline with how I drive. A V-Twin is not a drag bike or racer so I throttle up normally. I am going to pick it up later today and test ride it on the road. But I think I have it fixed for now and by going through all the suggested actions the problem seems to be fixed as long as I don't get into any drag races. Will keep you up dated on how it runs and behaves.
Thanks for everything
Charlie
 
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