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Thread: Intermittent Very Rough Running

  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.
    1983 R100RT hacked w/Cozy Rocket My blog
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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?
    1983 R100RT hacked w/Cozy Rocket My blog
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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.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
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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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    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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    Quote Originally Posted by 44006 View Post
    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.
    If I am not mistaken, when the fuel taps are on "reserve" setting, they are draining from the very bottom.

    Since water sinks to the bottom, it will come out that way.

    Also, a little "dry gas" will absorb water and allow it to be burned along with the gas.

    I think the best is to remove the petcocks from the tank, and flush out tank, clean petcocks, and re-install.

  10. #10
    Administrator 20774's Avatar
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    Quote Originally Posted by jimmylee View Post
    If I am not mistaken, when the fuel taps are on "reserve" setting, they are draining from the very bottom.
    Maybe, maybe not. A "normal" petcock has two straws that stick up inside the tank. The taller straw is the main tank; the shorter straw is the reserve tank. Below the shorter straw is gas/debris/water you rarely get too unless you clean the tanks or take the tank off and roll one side gas into the other, thus making it higher than the shorter straw.

    Now, if a PO removed the shorter straw, then you are getting to a point where it does actually drain from the very bottom. Typically, that's not the way the tank is set up.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Quote Originally Posted by 20774 View Post
    Maybe, maybe not. A "normal" petcock has two straws that stick up inside the tank. The taller straw is the main tank; the shorter straw is the reserve tank. Below the shorter straw is gas/debris/water you rarely get too unless you clean the tanks or take the tank off and roll one side gas into the other, thus making it higher than the shorter straw.

    Now, if a PO removed the shorter straw, then you are getting to a point where it does actually drain from the very bottom. Typically, that's not the way the tank is set up.
    You are right. I forgot about the two straws!

  12. #12
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    Only way to get ALL the gas/oil/water/crap out of the tank is to wipe out with something or take inside and wait for about a week for it to evaporate

    I have experience with commuting in very cold weather in northern wis - long time ago but some things you
    do not forget. My rig at that time was R69S/PopDryerHack With 5/30 oil it was good to go when neither my truck or wife's car would start at -20F or a little colder and was near impossible to get stuck seriously because you could just pick up the sidecar wheel and drag the outfit 180 deg and drive out the way you came (much younger and stronger then!!)

    Water in the gas/carb was a regular irritation
    Water freezing the throttle cables was another problem - cables much better now with plastic liner

    I looked at OPs Blog and see pic indicating that he has inline fuel filter (not needed) and this MAY cause a problem with water freezing in the filter - I do not want to start the filter arguement over again - we all said what we think but in this case for very cold weather the OP must also somehow make sure fuel flows freely through the filter

    It is not so easy at subfreezing temps to pull the rubber hose off the carb and check this - so again in my opinion best get rid of the filter which only adds another potential complication in the cold

  13. #13
    #4869 DennisDarrow's Avatar
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    Been gone a couple of days; but YES.....the ONLY way to clean the tank of both debris and WATER is to take off the petcocks, remove the tank, blow it out, and let it dry out a couple of days. I guess one could hurry this up with the wife's old fashioned hair dryer hose.........

    Also.......to me, in cold weather like +5 degrees, the water that was in the bowl is drawn up into the enricher/choke system. Remember a couple of weeks ago with the split tube that feeds the choke system? Supposedly water freezing did that, and for me, the OP is riding in cold weather, the water in the carb freezes in places and also causes the stumbles..............For sure, water is clinging to any oil that is gathered in that right side carb around the main jet........Perhaps blowing out the passages and for sure put the whole thing back together with some good "Techron" in the tank and ride for a hundred miles or so.........God bless.......Dennis

  14. #14
    Registered User krpntr's Avatar
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    If there is water in the bowls, you might want to go one extra step and inspect your main jets. I always get a bit of oil/water slime clinging to the atomizer in the winter from condensation mixed with blow-by, and I find a quick cleaning of the jets whenever it starts to stumble a bit clears the stumble up.
    If you can see water flowing out of your reserve tap, then there is a lot of water in the bottom of the tank and you may want to pull the tank and give it a good cleaning and inspect for rust in the bottom seam.



    82 R100s, 92R100RT

  15. #15
    Registered User richardak's Avatar
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    Thank you everyone for the responses and great recommendations. I did remove the main jets and blow compressed air through them and the jets were clean, i.e. no gunk behind them. I added Heet to the tank and shook the tank to mix it in. I had drained and cleaned out the tank last year to check for rust and I will do it again once I'm done for a while i.e. when the temperature drops below maybe -20F. I need to do all my annual maintenance anyway.

    I rode the bike in to work yesterday -6F, and it sat outside all day. When leaving, it started right up and exhibited none of the symptoms that I had earlier in the week. It ran great.

    BTW, the bike starts and runs great at these temperatures though I do run a much larger battery (group 24) and use 5w30 oil.

    Thank you again!
    1983 R100RT hacked w/Cozy Rocket My blog
    2012 Ural Patrol
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