Tighten your bolts!

Discussion in 'Frame Mounted Engines' started by likearock111, Jul 22, 2008.

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  1. likearock111

    likearock111 Guest

    Hey MBers,

    I just wanted to put a little note up here regarding my own difficulties with my 70cc 2-stroke, so maybe other people can learn from my mistakes. Always Always ALWAYS check your bolts for tightness after every ride. I used to be in the habit of checking them every 8-10 rides or so (most of mine are short, ~5 mile joyrides). Not only was this bad for performance, it was also probably pretty unsafe. Well, I've changed my ways.

    A while back, my engine started having the typical "bogging" symptom after a certain amount of time spent at WOT. The threads on here pointed me toward checking the carb and checking for air leaks. So, I took apart the carb, cleaned it, rebuilt it, replaced the black rubber o-ring I had installed between the intake manifold and the carb, and sealed it all up extra tight. I also replaced the intake and exhaust gaskets.

    None of this worked. And, on top of everything, it started leaking black semi-burnt fuel/oil. In the process of trying to figure out where the heck the black stuff was leaking from, I discovered that one of the bottom 4mm bolts that holds on the left-side front cover had completely fallen out, and the other three bolts were pretty loose. I don't know what you call this cover, but it's just in front of the cover that goes over the drive gear. So, long story short, I replaced the missing bolt, LocTited all of the main bolts on the engine, and now my engine runs better than ever!

    So, moral of the story: check your bolts! It might save you some frustration, money, or even some road rash.


    PS: Mods, this may go better in the 2-stroke section, since it has to do with HT performance. I was just thinking that tightening bolts is more generally applicable than just 2-strokes. Either way.
    Last edited by a moderator: Jul 22, 2008

  2. likearock111

    likearock111 Guest

    I decided to replace my fuel line today. When I went to twist off the auto-grade rubber fuel line from the petcock (using very little force), the stock petcock literally broke in half at the base of the threads, next to the gasket. :( Must've been a hairline crack there, or something. At least it didn't take too much effort to fish the threaded portion out of the hole, though. Now I need to try to hunt down a 10mm, 1.0 thread pitch fuel petcock before this weekend.

    Any suggestions? Do moped stores carry these things?
  3. BradJ80

    BradJ80 New Member

    Might be a bit difficult to find a M10x1.0 threaded petcock quickly. Perhaps you could locate a M10x1.0 barbed hosetail fitting from a industrial fittings/plumbing supplier, and buy an in-line petcock?

    Hopefully you can get the broken off section out of the tank.

    Also, I used loctite on EVERYTHING. Be careful which loctite you use because some loose strength with heat.
    I also replaced most bolts and nuts with quality locally made parts.

  4. Mountainman

    Mountainman Active Member

    Kind of wondering about these petcocks -- my friends broke in the same place -- not even a hundred miles on his MB... Anyway -- if needed an easy-out should make for quick removal of broken part in tank -- handy tools to have around... Your local lawn mower shop may be the fastest place to find a new petcock - or Napa Auto Parts -- if you are not wanting to wait for UPS from the web... Happy Riding from - Mountainman
  5. I believe reading other posts from Pablo the petcock is 1/8'' npt...
  6. likearock111

    likearock111 Guest

    There's a lot of good input here. Thanks, Brad, Mountain, and Mister! I think I'll see what my local Napa can do for me, and maybe go the hosetail + in-line petcock route.
  7. Skyliner70cc

    Skyliner70cc Active Member

    The stock petcocks often break if overtorqued. It often is necessary to overtighten the petcock to get that stock junk gasket to seal properly. I use a softer gasket and use threadseal so I can tighten the petcock to a reasonable level without worry of a leak.
  8. D_M

    D_M Member

    When I went to Lowe's yesterday to hunt down a chain (no luck), I looked through their small engine aisle (the one with the chainsaws in my local store). They have a selection of small engine repair/maintenance parts, like Briggs-Stratton filters, etc. They also have some fuel filters and a package that says something like "universal fuel hose with shut-off." Looked like it would work.