stumbling Idle

Discussion in 'Engine, Fuel and Exhaust' started by blueharley, Apr 1, 2009.

  1. blueharley

    blueharley Member

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    this what I got just bought the bike for the wife Bike had a miss in it thur all rpms Changed out the worn out Carb with an S&S .072 main .295 inter jet ran better but still had the miss and didnt idle any better so changed out the total Igintion system back to stock, wiring harness and all the rest went to time it and couldnt get a stable timing mark due to the rough idle now checked VOS switch found it was bad replaced it now I can see the timing mark but it is still not a good idle runs real rough on idle but above 1500 rpm smooth as a new borns butt when I pull the Vac line on idle engine smooths out I guess the ? is no telling how long this bike was running with the vos switch bad did it do some damage to the top end valves are semi carboned up the new plugs are sooty black after and the engine seems to be running on the rich side there is nothing wrong with the carb or the ingnition system took all that and tried it on my other fxr ran fine did the valves burn from running with no advance for god knows how long Did a compression test shows 110 to 120 psi

    PS its an 1985 FXR 1340 evo motor
     
    Last edited by a moderator: Apr 1, 2009
  2. glider

    glider Veteran Member

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    Running without the VOES probably didn't do any damage in itself but with the vacuum line open the mixture was lean and the possibility of burning a valve is pretty good although you have decent compression. Not quite sure if there was another question in there :D
     
  3. blueharley

    blueharley Member

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    well the next step is pulling the heads I know the compression is "ok" on the old vos switch it was bad but why it was bad it wouldnt hold a vac so this engine was sucking air from the switch running lean for god knows how long which makes me think by putting the new carb, the new igintion system now that all is working up to par that I uncovered another problem just trying to keep heading in the right direction ,this bike has been trying to say the least, no matter what I do it just wont idle steady and is very rough except when it is over the 1800 rpm range but then it still has a miss in it
     
  4. glider

    glider Veteran Member

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    Have you checked the intake for leaks?
     
  5. KingHeritage

    KingHeritage Junior Member

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    It seems you still have a vacuum leak somewhere
     
  6. blueharley

    blueharley Member

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    yep checked the intake for leaks even pulled it apart and installed another set of gaskets even spayed wd 40 on the outside while running nochange with the stumbling rechecked the compression again with full open carb hot motor have 150 to 160 psi so I dont think its valve Maybe have a bad cam or lifter this problem is driving my nuts also this is rubber mount engine have checked ALL the grounds and added and extra 1 from the -on the battery to the frame and engine just for grins and giggles
     
  7. 7ender

    7ender New Member

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    is the stock camshaft still mounted in that engine ?,...sometimes it will give problems to adjust for a smooth idle .
    You better take the VOES out , otherwise it's very hard to adjust a low rpm steady idle.
     
  8. Dan89FLSTC

    Dan89FLSTC Banned

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    Do you have adjustable pushrods? It may be that a pushrod is adjusted wrong, preventing a valve from seating properly.