97 fxds conv cuts out and sputters at 3000 RPM

Discussion in 'Engine, Fuel and Exhaust' started by Fuzzymike, Jul 14, 2013.

  1. Fuzzymike

    Fuzzymike Member

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    I have a 97 dyna convt with 20k miles. The issue I am having is that somewhere close to 3000 RPM in 4th or 5th gear at highway speeds it is losing power and then cuts out and sputters. If you roll on the throttle it makes it worse if you let off the throttle it takes it a bit but it comes back and runs ok until you get back close to 3k rpm. Sometimes if you downshift to 4th it will run ok sometimes not. This issue does not happen consistently however which is why i am so perplexed. If it happened every time I could trouble shoot it easier. Some days it runs perfect other days it will start off good and then start acting up. It seems to have some coloration to when I shut off the bike and restart it. IE It ran great for 200+ miles and 2 gas stops then I stopped to take in some sites and as soon as I got up to 60+ Mph and 3000RPM the problem started again. I have changed nothing on the bike in the 10k miles since I bought it and it has only had this issue for the last 3k or so. Bike is stock except for Screaming Eagle air cleaner and cover, Exaust has been opened up, I know it has been re-jetted but dont recall the size. The tune seems good and plugs look good as well and have been changed. I have replaced the plug wires and drained all fuel and cleaned the carb. My first thought was bad gas or dirty carb but everything looked good and it does not explain how random this issue occurs. Once it starts acting up it will not come out of it unless you shut it off and that only works sometimes. All wires and connections look good and tight. I am not good at electrical troubleshooting so that is why I have not checked into that aspect of it yet.
    I have been told it looks like the ignition is starting to fail but figured I would see if anyone on here has any other ideas or a similar experience. I have looked through a ton of posts and have not found any experiences that quite fit what I am experiencing with this bike. Any thoughts are appreciated.

    Thanks
     
  2. HDDon

    HDDon Experienced Member Contributor Retired Moderators

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    There will be some sharper minds than mine coming on soon. First I would check the battery cables, both ends, to make sure they are clean and tight. It really does sound like it is electrical, since you have not changed anything. When you opened the carb you might have pinched the diaphragm at the top, but since the problem existed before probably not. Have you checked the screen on the petcock, inside the tank? Have you checked the fuel filter?
     
  3. Breeze3at

    Breeze3at Well-Known Member

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    It sounds like a fuel starvation problem. It doesn't happen every time, and sometimes after the bike has been shut off and restarted. I would look a the vacuum operated petcock. Maybe a crack in the vac. line, or bad diaphragm. Possibly a clogged screen in the fuel valve? Could even be a bad tank vent. Try loosening the gas cap when the symptoms start.
     
  4. Fuzzymike

    Fuzzymike Member

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    Thanks for the ideas I will go through the vacuum lines and double check the cables. I have tried removing the gas cap when this happens just forgot to say that. I will swap out the petcock to be sure but am not thinking that is the issue cause at times I can downshift and get over that 3000 area and run for miles in 4th at 65+ mph but as soon as I go to 5th and get back into that 3000 rpm area it cuts out again. I don't run an inline fuel filter as I have had issues in the past on my older bikes with vapor locking when using an inline filter.
     
  5. Jack Klarich

    Jack Klarich Expert Member

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    If this was ignition you could start it up let it idle preferably with a fan blowing on the cylinders, mist some water on the coil plug wires and the wiring coming out of the nose cone, does it change the way the bike runs? Another possible area could be the pick up assembly inside the nose cone and or the ignition module, tho I agree with other posts here it sounds more fuel related, does this tank have a vent hose and a fuel cross over?
     
  6. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

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    I agree with Breeze. When I first read it I thought fuel too. But you say you can get over that 3K rpm range and it runs ok. That would seem to rule out a fuel shortage. Jack may be on to something with the ignition.
     
  7. Breeze3at

    Breeze3at Well-Known Member

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    Yea, if it runs ok at higher rpm's, it's probably spark related and time to call in Hoople. :majesty
     
  8. Fuzzymike

    Fuzzymike Member

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    OK I just got back from a 100+ mile ride to test some of the changes I made. I went through all the wiring and double checked everything and had cleaned battery connections. Checked for but did not find any intake leaks and all vacuum lines looked good.

    I made it about 4 miles at 70 mph and was in the 3200 rpm range when It cut out again. I let off the throttle and downshifted to 4th gave it a second to come back to life and pumped the throttle a few times before rolling on it hard. It did fine and I settled in at about 75-80 mph and 4000 rpm for 10 miles or so. I went back to 5th and within 5 miles it cut out again. Same procedure repeated and same result. 50 miles down and I stopped for a couple hours to talk with some friends. Storm was coming so I figured this was a good opportunity to kinda check out some of Jacks suggestions. It ran good first 4-5 miles then cut out again. but not as bad only went to 4th for a mile or so then back to 5th and it was running good in the 60-80 mph range and 3-3800 rpm. The rain hit and the bike never blinked. Ran 30+ miles in rain from heavy to light. About 10 miles from home it quit raining and after slowing down at a interchange it cut out again a mile later. Downshifted to 4th again and this time it kept having issues down to 50 mph or so. Played with it a bit in 4th and 5th and after 3 miles or so it came back around. This last time like some times before when this happens if you give more throttle it makes it worse and if you let off it comes back to life. Next step will be to replace the petcock and give it another test ride. If nothing else making a change and then testing gives me a great excuse to go ride! Thanks for the suggestions everyone I will keep updating after every step.
     
    Last edited by a moderator: Jul 14, 2013
  9. Jack Klarich

    Jack Klarich Expert Member

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    Your bike uses a modified cam trigger pick up assembly in the nose cone, I believe there is a vacuum switch involved here for advance also, check any hoses you see around the carb and intake manifold also
     
  10. Jack Klarich

    Jack Klarich Expert Member

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    [​IMG] Here is a picture of the pick up