drilled hole too far to mount head and jug

Discussion in '2-Stroke Engines' started by bob123, Sep 21, 2016.

  1. bob123

    bob123 New Member

    any repair for this?

  2. Frankenstein

    Frankenstein Well-Known Member

    What on earth did you drill holes into preventing jug and heads from being installed?
  3. zippinaround

    zippinaround Active Member

    Curious about this too haha you drilled into the crankcase? Are you trying to put a 48 cc top end on a 66 cc bottom?
  4. bob123

    bob123 New Member

    going to install a heli-coil because of a stripped
    hole but went too far. I guess the crankcase is toast?
    Last edited by a moderator: Sep 22, 2016
  5. zippinaround

    zippinaround Active Member

    Sorry I don't know what that is , you mean the jug rods cross threaded the holes in the crankcase? Some pics would be good * just Google heli coil and reason I didn't know is because I call those threaded inserts
  6. bob123

    bob123 New Member

    Just 1 hole was stripped. I was going to install a thread insert but went a little too far
    with my drill. I wonder if I can go ahead with my plan and maybe use some Loctite or Jb weld to seal
    the hole. Any suggestions would be appreciated. If anyone has another idea that'd be great. I wouldn't mind buying a new crankcase if they're not too expensive. Just the case. And yes, they are the four very long studs that go through the head, jug and then in to the crank case.
  7. zippinaround

    zippinaround Active Member

    that'll prob be ok the bolt should seal it if you loctite it into the thread insert maybe loctite the thread insert into the crankcase too?
  8. Frankenstein

    Frankenstein Well-Known Member

    No no no, don't lock tight it, you really shouldn't lock tight a helicoil. As far as drilling too far just get some jb weld and a bit of grease on the end of the bolt, drive the bolt almost all the way in, stop where it normally stops, use another bolt in another hole to figure that out. You will need to split the case for this part. Put jb weld into the hole from the back, and try to avoid letting air bubbles form. The grease keeps the epoxy from grabbing the bolt.

    Option 2: if you don't care about being able to remove the bolt in the future, put strong tape like gorilla tape on the underside of the hole inside the crankcase, this is way easier without a crank in the way but do as you see fit, put a blob of epoxy the size of a quarter into the hole and torque the bolt in but not farther than it would normally go. Once it is set its set forever but won't leak.

    Final option is put a tiny bit of tissue or toilet paper into the bottom of the hole, then fill only the bottom of it with a milliliter or 2 of epoxy. To do it accurately get one of those cheap baby medicine or pet medicine dispensers, looks like a syringe. They even have milliliter marks on them how great! So put a drop of water, A SINGLE DROP, down into the hole to wet the tissue, pack it down with a smaller bolt, put epoxy in and wait for cure, afterwards you can use the helicoil as normal and remove the bolt if needed, leave the tissue it will disintegrate in time harmlessly.
  9. bob123

    bob123 New Member

  10. bob123

    bob123 New Member

    Thanks for the very detailed repair ideas. Have you tried any of these? I really appreciate
    it. I have one more problem I didn't mention, because I didn't notice till recently. When I
    drilled the hole too far, I scored the top side/corner of the crank. Maybe this will help with the balance issues I keep reading about. The glass is half full, until I drink the rest of my beer.
  11. crassius

    crassius Well-Known Member

    my main concern would be tailings that fell into the case - they might be stuck in the bearing cage where they could lock up the motor at some point when they work loose

    consider a new motor with the old one just for parts
  12. bob123

    bob123 New Member

    I turned the motor upside down and sprayed a whole can of brake
    kleen in there and now my plan is to fill it with gas/oil mixture, swoosh it around a bit
    and do that again dump it out and cross my fingers. I have a new motor I ordered yesterday
    that hopefully will arrive shortly, so I have everything covered except Murphy's Law.
  13. Frankenstein

    Frankenstein Well-Known Member

    Oh yeah that damn Murphy getting his dirty gremlins in everything.

    I don't think the crank is a problem but I also didn't know you drilled a hole the far into the crank, I used the tissue idea on a helicoil in a transmission case that had been drilled too deeply, far as I know they haven't had problems with leaks, and that hot atf can dissolve some pretty tough stuff with time.

    I think that you will have problems with the shavings being in the motor unless you litteraly split the case and do a full scrub. It is your motor however, I just know the wrist pin bearing is really rather delicate to contaminants, once it starts failing it can take the rest of the motor down with it pretty quick, imagine the shrapnel of half a dozen hardened steel pins being dragged through your main bearings, con rod big bearing, and across your piston, rings and cylinder at 5000 rpm... A few seconds of that and the engine's toast.
  14. Steve Best

    Steve Best Well-Known Member

    Hey Bob, the spraying Brake Kleen into the cylinder is 50% likely to be successful in my experience.
    A cast iron cylinder will swallow aluminum chips without worry but these chromed aluminum cylinders will score easily.
    For the effort and expense, good idea to disassemble and clean out the bottom end if you are ever in doubt if anything is in there.

    I have locktited and epoxied helicoils in for various reasons, however never on one of these motors.
    Some of our industrial situations had helicoils in places that had fasteners in and out on a regular basis. The helicoi would often "walk" out and be exposed. We'd cut them off with a die grinder, clean out with spray cleaner and seal it in place with locktite or "crazy glue". Epoxy was reserved for the spots where the threads were likely to leak some sort of gas or fluid. The usual method was tap it out with the Helicoil tap, spray it clean with Brake Kleen or similar, putty it up with the epoxy and ram the helicoil in place. Clean up the coil driver well. Normally allowed 24hr cure time with a greased bolt in place. Never relied on a plug of epoxy to seal the bottom unless it was 2 thread diameters deep or more. Any less will be pushed out by the stud or hydraulic/pneumatic pressure.

    Helicoil it, epoxy or locktite it if you wish, and/or daub a little RTV or similar on that stud when you assemble it. You will be fine.

    Be more careful in the future, I am now! :)