HT cylinder head bolt problem

Discussion in '2-Stroke Engines' started by fishhead, May 4, 2009.

  1. fishhead

    fishhead New Member

    One of the bolts on the cyclinder head is not secured down in the engine case. When I try to tighten the nut on the head the bolt will pop up....
    The other 3 are good and the engine is running OK.
    I removed the head and tried to tighten the bolt into the case, but it keeps popping up. I suppose it need to be tapped out, but that would take a real long tap.....

    Has anyone seen this before ?

    Wondering how this happened. Any fix ideas ?


  2. Shadeslay

    Shadeslay Member

    Sounds like it's striped, you could try the next size bolt. But are likely better off re-threading to the next size. I've even read you could jb weld it in, but if you do that make sure it's a high grade bolt, if it breaks you're in bad shape.
  3. heathyoung

    heathyoung Member

    The tap doesn't need to be too long - you remove the head and cylinder and tap into the block.
  4. machiasmort

    machiasmort Active Member

    I bought a motor off of flea bay and it had a stripped head bolt ,remedy:

    Go to home depot and buy a length of 1/4 X 20 threaded rod...

    Remove the cylinder head (jug), the thing the piston rides up and down in.
    While doing this be careful not to hurt the gasket between the block (lower end) and the jug. Do this by slowly trimming arround the edge with a sharp razor knife! Work the knife between the jug and gasket (leaving the gasket attached to the block).

    Remove the bad rod and with a flat bottom tap, tap the stripped hole out 1/4x20 and thread your new rod in after adding loc tite.

    The 1/4 20 rod should fit right up through the hole in the jug. Reassemble being careful not to bust the piston rings! They might have little nobs in the ring groves, so make sure the groves line up with the ring. Busting a ring is easy!

    Good luck!
  5. machiasmort

    machiasmort Active Member

    PS - don't forget to wash the chips out! Use pre mix gas but be careful (fires).
  6. Pablo

    Pablo Motored Bikes Sponsor

    Just a FYI. 1/4-20 rod won't work if you have 8mm studs.

    fishhead - Not sure exactly what you mean by "popping up" - are you using the cap nuts? Does the stud just spin in the engine case blind hole?
  7. Junster

    Junster Member

    Are you familiar with Heli-coils? It's a kit that comes with a special tap and a precut steel coiled thread. You tap the hole then using the threadlocker you screw the steel "thread" into the hole. The new thread in the hole matches the old thread. They work great. I just don't know for sure if they make them for metric threads. I'd have to question heat expansion. Having one bolt that was a different material or different size then the others and not "growing" in length the same as the other 3. But maybe these motors just aren't precise enough for that to matter.
  8. machiasmort

    machiasmort Active Member

    I did it to mine Junster (works fine) w/ old head gasket also!

    Good thought tho!