My bike is not running smooth - advice needed

Discussion in 'Softail Models' started by Piotra, Aug 10, 2012.

  1. Piotra

    Piotra Active Member

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    My motorcycle (100 inches RevTech engine, Mikuni carb HSR42) broke down. It drove 1100 km with no problems. And then after one night motorcycle did not want start. I used the choke but I needed also increase revs beacuse it did not want to run. Since then the bike runs bad, I can not adjust revs, I have to set it high than proper because if it is correct than engine stops.
    I think that it can be carb. I found that screws that hold intake manifold to heads were loose. Between intake flange mountings were abuot 0,5-1 mm of space. I inserted allen wrench and I could screw the bolts with just one finger.
    I tightened it but the bike is still running bad. What to do??
     
  2. fin_676

    fin_676 Well-Known Member Staff Member Moderator Contributor

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    Where the manifold connects to the head there is a seal that prevents air being drawn in at that join with the screws being loose then the seals may have got damaged
    if air is drawn in at that point it would create a weak mixture and the engine may run as you have described
    remove the carb and manifold replace the seals and use some loctite on the manifold screws so that they do not get loose again

    Brian
     
  3. Dr. Dolittle

    Dr. Dolittle Experienced Member Staff Member Moderator Contributor

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    Bad gas?

    Did you fill up just prior to this happening?
     
  4. xcavater

    xcavater Member

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    Intake manifold gaskets did not seal when you tightened. Remove and replace gaskets.
     
  5. Piotra

    Piotra Active Member

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    Ok, so I will replace the gaskets. I have to order it.

    First I was thinking that it can be bad gas so I drained all gas from tank and filled it with other from other gas station. It didn't help.

    Is any easy way to check if the gaskets are damaged? I read about spraying WD40 close to the manifold while engine is running. It should change revs. Is it good idea to check it using WD40 or if I will do this test and nothing happen it not really mean that gaskets are good?

    Last question. If I will install new gaskets should I use any lubricant on them or maybe silicone???
     
  6. xcavater

    xcavater Member

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    Most any aerosol sprayed in the vicinity of the gaskets will work. WD40, carb cleaner, etc sprayed with engine running. You are listening for a change in engine rpm. Be sure that the overspray isn't going through the air cleaner or it will give you a false reading.
    I don't like silicone unless it's called for. I use Permatex aviation gasket sealer on any gasket but the cylinder head.
     
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  7. 89stroker

    89stroker Active Member

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    Just finished getting a problem dealt with recently, my bike did have different symptoms than you but in the end a leaking intake manifold seal was found. I had used carb cleaner to diagnose but could not get much if not any of a change in RPM. When I finally tapped and said "uncle" and took to the dealer, they used a non flammable brake cleaner to check the seals. Stalled the bike immediately when they hit the back flange. This will me the method I used from now on. Just sharing what worked for me.......:s
     
  8. Piotra

    Piotra Active Member

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    I checked manifold with WD40 and nothing happened. But I have one more idea what can be a problem.
    I watched this video (it's not my bike):
    98 Harley fxd mikuni hsr 42 problem - YouTube
    I looked at comments under video and I'm thinking that I can have a problem not with carb but with the coil. I have single fire Drag Specialities coil. During my use of the bike during last 300-400 km two times I feel something like breakdown current when I rode a bike. And during last ride when the bike was warking bad I feel breakdown current few times. It looks that when a bike is running coil is not giving the spark each time. When there is missing spark than next spark can give louder explosion because there is more gas mixture in cylinder.
    So let me know. Is any way to test this type coil. It wouldd be easy to test if the coil is working or not working. But it seems that coil also can work not correctly. Of course I can buy new coil but I would prefere to test it before.
     
  9. Hoople

    Hoople Account Removed

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    So let me know. Is your coil Single fire? Dual fire coil? Does your engine use a cam sensor? Who's ignition module are you using. If HD, what year is it.
     
  10. Piotra

    Piotra Active Member

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    My coil is single fire and ignition is Ultima, I do not have cam sensor. It is very simple wiring and it worked correctly more than 1000 km.