burnt oil on top of piston.

Discussion in 'Engine, Fuel and Exhaust' started by fattyboy, Jan 23, 2014.

  1. fattyboy

    fattyboy Active Member

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    Hi,All Its been awhile been alittle under weather.Still working on 03 fat boy.Rebuilt motor put a 100 miles on it and pulled plugs and took a bore scope and looked at pistons,Front piston lookes like it has some what burnt and wet oil on top and back piston not as bad.Plugs are a light brown.Is this noemal for a new motor? Please Help!!!
     
  2. Jack Klarich

    Jack Klarich Expert Member

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    Do you have Screaming Eagle air cleaner or after market one directing the breather hoses into the throttle body?
     
  3. fattyboy

    fattyboy Active Member

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    no i have the arlen ness where the breathers go into the head.
     
  4. Jack Klarich

    Jack Klarich Expert Member

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    OK, but the oil mist goes where? to the backing plate or directed to the throttle or do you have hoses hanging down to a seperate filter or catch can? Reason I ask is the oil mist can get sucked in to the intake and end up on top of the pistons and glazed over in the intake also, open up the throttle plate and have a peek inside the intake just for grins
     
  5. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

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    If its a Big Sucker, it vents into the air cleaner via the hollow bolts.
     
  6. BUBBIE

    BUBBIE Well-Known Member

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    Only 100 miles on a fresh top end WILL have a little oil on the pistons. Usually after 500 miles it should have seated all and no further by-pass should be there. I would suggest to try to get the engine intake venting changed soon. On my 09, it showed a lot of Un-necessary carbon build-up also before my new build on my 09 King to 103" and Lazy me..... No Change yet. Soon Though. :s

    signed....BUBBIE
     
  7. fattyboy

    fattyboy Active Member

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    Hey Bubbie, It is a arlen ness big sucker,You said i should think about changing the venting on this motor,It does vent threw the bolts that screw into the heads.What do you suggest??? Thanks Bubbie.
     
  8. Jack Klarich

    Jack Klarich Expert Member

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    The breather bolts on the heads are hollow and transfer the oil mist thru the backing plate via a channel in the backing plate. The head breather bolts also known as banjo bolts could probably be modified with brass elbows and hoses routed down the back of engine to a catch can or a remote vent filter on the end of the hose. This to me would be a lot of extra work, J M O
     
  9. fattyboy

    fattyboy Active Member

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    Thanks Jack for the input,Do you think thats where the oil on the pistons is coming from,From the breathers?The motor has a new cvo crank,Bigger bore cyls.that are 20 over new pistons rings bearings seals gaskets.the heads are se cnc ported,when we tore the motor apart the old pistons were pretty clean like it was running lean.So i dont think it could be a valve proublum or guide proublum.I think the old pistons would have the same proublum.
     
  10. dolt

    dolt Senior Member Contributor

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    If you hadn't looked, you wouldn't know and you are comparing pistons in "broken in" condition to pistons with 100 miles on them. If the motor wasn't head cycled and/or a good break in run hasn't been done, don't worry about it. Get the motor up to temp, out on the road and get several hard pulls through the gears up to 4th, let the motor decal, down shift to second and to it again; rinse and repeat. It takes heat and compression to seat the rings and it sounds like they haven't seated yet. Rings can be seated in 50 miles if done properly.

    Or get the bike on a dyno and do the pulls on the dyno so AFR can be checked, and adjust as required.

    Don't look again until you have about 500 miles on the motor. The only way you can judge the condition of a top end is with compression and leak down testing. I think it premature to start thinking there is a problem but, if you do, do the testing; looking proves nothing.

    Venting to the atmosphere is not a lot of extra work and well worth whatever work is required. Starting point is drilling and tapping the backing plate for some barbed fittings, or finding some of the early breather bolts and fittings designed to attach hoses like on the early models. Block off the holes in the backing plate where the head breather hoses enter the backing plate and connect new hoses to the barbed fittings and route them to wherever you want to vent; a catch can, filter of just vent them to the atmosphere. Lot's of different ways to do it.

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