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Thread: Intermittent Very Rough Running

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  1. #1
    Registered User richardak's Avatar
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    Intermittent Very Rough Running

    Looking for some help from the airhead gurus on this site.

    Three times this in the last two months, my '83 R100RT has ran really rough. In all three cases, the temperature was around +5F. The first time, I was accelerating down the road and when I reached about 45 in 3rd, there was a sudden loss of power and a vibration. It almost felt like maybe it was running on one cylinder. I made it home at 40 mph as there wasn't really any traffic. An hour later, it ran fine. I was guessing possible water in the gas since it had sat outside for 9 hours. BTW, no problem starting at these temperatures. I added some Heet to the gas tank. The next day, I rode it to town and at about the same speed, a smaller loss of power and some vibration within a mile of starting. I turned the enrichener to full and it went away. After another 1/4 mile, I turned the enrichener off and all was just fine.

    Yesterday, it happened again and turning on the enrichener again, allowed me to get home but it wouldn't idle and would alternate between low power and normal. Very unnerving when riding uphill on snow as the pusher would start spinning when the power came on. As would be expected, it was running very rich when I arrived home but would barely run when the enricheners were turned off. Before it happened, no problems and even stopped a few times to take pictures.

    This morning, everything normal again. Hard to debug as the engine won't idle. Normal running, the plugs are a nice light brown. After one of these incidents, very black but not wet. Lots of fuel running through the engine as my last gas mileage check was only 21 versus the normal 28.

    Any thoughts? I was wondering if a bad bean can, ignition module or coils would behave like this? The carbs were rebuilt last winter and I've put on about 4,500 miles since then. They were rebuilt since it was behaving like this last winter and I assumed carbs. After the rebuild, it didn't happen again until October when it started getting cold again.

    Valves are adjusted, heat sink compound redone on the ignition module, carbs rebuilt, new fuel filters, tank clean. All of this checked or done this past 6 months and none right before any of this started happening. I did check the coils for cracks last year and couldn't find any but I wasn't really sure what I was looking for. The bike has been in regular if not daily use since last April.
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  2. #2
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    I am guessing, but my vote goes for something in the fuel system - water in carbs? I don't see how it could be ignition if using the enricher changes things.

    Drop the fuel bowls, and let fuel flow freely through and see if anything could be causing it.

    Have you purchased fuel lately? Bad fuel?

    Hmmmm?

  3. #3
    #4869 DennisDarrow's Avatar
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    OK........To me, it is definately fuel related. Can you isolate which side this is happening on? When you remove the bowls of the carbs any globs of water? If you remove the main jets any globs of oil/water yuck?..................More in a bit and there will be lots of folks on this........But for me it is temp/water related and water is in one of the many passages and freezing?..........God bless.....Dennis

  4. #4
    Registered User richardak's Avatar
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    I will drop the fuel bowls this afternoon and report back.

    I believe the enricheners draw fuel from a different circuit in the Bings. Is this correct?
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  5. #5
    Administrator 20774's Avatar
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    Yes, the enrichener is a small carb stuck on the side of the bigger carb.

    I'd be sure your valves are set properly before going any deeper. You have the '83 model which is in the middle of the range where the seat metallurgy was lousy for transferring heat. Result was valve face damage over time. Poor idling is one of the symptoms of valve clearance closing up. It could translate to some of the other issues, but it's really noticeable at idle.
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    I would also check for intermittent air leak. Like a vacuum tube that has a crack and only periodically leaks.

    Also the suggestion above is great - try to isolate which side is causing the problem. Or both sides. If both sides it would sound like fuel because it is affecting both. If one side, probably something on that one carb.

    Tight valves usually show when engine is warmed up as everything expands due to heat, and valve gap is taken up. This is really evident when starting after hot. Loss of compression - doesn't suck fuel.

  7. #7
    Registered User richardak's Avatar
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    Quote Originally Posted by 20774 View Post
    Yes, the enrichener is a small carb stuck on the side of the bigger carb.

    I'd be sure your valves are set properly before going any deeper. You have the '83 model which is in the middle of the range where the seat metallurgy was lousy for transferring heat. Result was valve face damage over time. Poor idling is one of the symptoms of valve clearance closing up. It could translate to some of the other issues, but it's really noticeable at idle.
    The heads were already done by Ted Porter a couple of years ago and rarely do they need even a minor adjustment since then. About 15,000 miles on the bike since then.

    Quote Originally Posted by jimmylee View Post
    I am guessing, but my vote goes for something in the fuel system - water in carbs? I don't see how it could be ignition if using the enricher changes things.

    Drop the fuel bowls, and let fuel flow freely through and see if anything could be causing it.

    Have you purchased fuel lately? Bad fuel?

    Hmmmm?
    That was it! I dropped the bowls and there was water in each bowl. From the right side of the tank. I drained about a cup of gas from each petcock and got a little water from the right side. I generally only switch the left petcock to reserve before getting to the gas station.

    Thank you all for the help! Now just need to wait until the "winter storm" passes through. A foot of snow is a bit much for this 1WD airhead hack.

    carb.jpg
    Last edited by richardak; 11-14-2013 at 12:01 AM. Reason: Added photo
    1983 R100RT hacked w/Cozy Rocket My blog
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  8. #8
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    I suspect you still have water in the tank below the level that is drained by the fuel taps.

    Suggest you drain the tank completely and sponge out all the gas/water remaining in the bottom using perhaps a piece of rag firmly attached to wire of coathanger or similar.

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