engine spitting oil

Discussion in 'Motorized Bicycle General Discussion' started by KeysCruiser, May 2, 2011.

  1. KeysCruiser

    KeysCruiser New Member

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    taking bike for ride and noticed oil coming out of top of engine and all over my leg spurts of it not alot but enough. 3rd tme riding wondering whats going on?
     
  2. Bob Mac 18704

    Bob Mac 18704 New Member

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    You need to get a good exhaust gasket and torque it down and check it regularly
     
  3. DaveC

    DaveC Member

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    It's leaking around the cylinder head gasket. It most likely needs to have the head torqued down again, a normal procedure. Sometimes even when torqued down right they still leak due to an uneven gasket surface. Check the mating surface for dips or grooves. They can be sanded out by using 220-400 grit sandpaper fastened down to a piece of glass for flatness. Oil the head and make figure "8" passes. At regular intervals, like every 5 "8"'s turn the head a quarter turn to keep things even. Do this enough on the head it will raise the compression but that's not what we're after here :) all we want is a flat surface.

    For a more dependable seal use something like Permatex Copper Spray-A-Gasket on the gasket. It helps to seal it better. Get rid of the acorn nuts. They can bottom out and cause false torque readings or even cause you to pull the threads right out of the block. Get some good nuts from a bolt store or Lowes or Home Depot, where ever. Just don't use the stock.

    I have a new 49cc HT motor coming. Even before it gets here my new head stud set from Sick Bike Parts arrived. I also tap all the holes out. The Chinese have a bad habit of not tapping the holes to the bottom. That causes stripped threads due to there not being enough thread engagement.

    The torque differs according to the size of the bolt. A 66cc has a M8 size bolt and the head studs need to be torqued to 15 lbs as a good number and for the 49cc M6 bolts 8 pounds is enough. Use a "Z" or "X" pattern to torque the bolts, don't just go around in a circle. That causes uneven torque application and can cause a warp in the head. dnut
     
  4. fall_down_stand_up

    fall_down_stand_up New Member

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    Dave C,I think 15 pounds is a little to much,I wouldnt torque it more than 12 to 13 pounds(dont want to strip the bolts)....
    John
     
  5. DuctTapedGoat

    DuctTapedGoat Active Member

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    If you replace the studs you can hit 15 ft/lbs. But I wouldn't go past 12 with the stock.
     
  6. DaveC

    DaveC Member

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    Anyway, My Boy Go Fast motor called for 12.5 lb/sq.in. Others here have said as much as 18 which is high. I went to 15 lbs when I put on the Hi Compression Puch head on SBP studs. Plus I tapped the block to make sure the threads bottomed.

    When I torqued to 12.5 lbs I went up in 2.5 lbs stages, 2.5 to 5, 5 to 7.5, and so on until 12.5 was reached, rode for 100 then re-torqued to 15 cold.

    I'll be pulling the head today to put it on a new 49cc. I really want to look at the mating surface. Stock there's a raised ring around the combustion chamber that crushes when torqued due to the fact it's made from "dead soft" aluminum. It's very soft so it does crush but the ring feature does not exist on the Puch head, it's just flat surface to flat surface. Plus that will give me the chance to get out my combustion chamber measuring stuff and find out for sure the volume of the chamber so an accurate compression ratio can be determined. I've been running under the assumption that the C/R is around 13:1, pretty high :p. On the 49cc motor it's supposed to run at 11:1 or so but I really want to know.

    I'll be rebuilding the 66cc with guidance from Daniel Maia's and jaguar's threads on rebuilding and porting, including epoxy intake product MADE for intakes to change transfer port angles. You can look a Puch and Morini bottom cylinder gaskets and see the port angle is different than the HT one.

    oops, it's early and I ramble ;)
     

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