Spark Plug Burning Too Hot - Hole In Piston

Discussion in '4-Stroke Engines' started by Mountainman, Jul 27, 2008.

  1. Mountainman

    Mountainman Active Member

    If spark plug is replaced with one that burns much hotter can it burn a hole in the piston ? I was looking for a replacement plug for my Subaru 33cc and the gentleman working at a small engine repair shop did not have the exact plug - so he attempted to cross reference - nothing came up. He said that it would not be a good idea to just put any plug in my engine (even though it may look the same) if a plug burns to hot for said engine -- IT MAY BURN A HOLE IN PISTON. Well - I also worked in a small engine shop - for a short time - some 25 years ago - and don't remember any such problems. But - I am thinking - best - to get the correct plug. Happy Riding from - Mountainman

  2. Skyliner70cc

    Skyliner70cc Active Member

    Unlikely, that it will but your main problem will be preignition due to fact plug doesn't dissipate heat as well. Preignition/detonation can cause engine damage (you know, the pinging rattling sound you hear sometimes when you step on the gas in your car).

    I'd use the plug but this is one of the rare times you may want to use a higher octane fuel.
  3. jesse8931

    jesse8931 New Member

    actually it will i had an old suzuki 50cc dirtbike and replaced the junk spark plug with a ngk br8es and it put a huge hole in piston
  4. Mountainman

    Mountainman Active Member

    Hi Skyliner -- I have noticed some of this going on - on the lower end of my revs - engine rattling.. Subaru said to use regular gas. Suffering from - slight loss of power and occasional missing - with carb air filter getting somewhat wet with gas ?? Mountainman
  5. What plug you need? I had a time searching for a plug and I found mine at my local Harley dealer. Under 2 bucks for a resistance plug with a 5 number.
    Check out your local motorcycle shop. You might be surprised.
    And it's a great conversation starter if you pull up on your bike.
  6. Skyliner70cc

    Skyliner70cc Active Member

    I'm assuming you have a 2 stroke? If so, its not unusual for differences in performance at certain rpms due to the fact that 2 stroke porting/timing is optimized for a certain rpm and desired engine characteristic. This means operation at all other speeds is compromised a slight degree.

    It wouldn't hurt to try a new (colder heater range) plug or higher octane. If it works, then that is awesome. If it doesn't then try something else. I believe in ruling out the simple stuff first before looking for complex solutiosn to engine issues. Good luck w/ your ride.


    PS As time goes by, carbon build up on a piston can cause preignition. This is why older cars often have "spark knock" when accelerating. Higher octane fuel or breaking the carbon loose by spraying water into intake are some options to try. Note: spraying water into intake on any engine is dangerous and risks engine failure and should only be done by someone mechanically experienced. Nothing worse than breaking a rode from hydrolocking an engine. Small engines would require nothing but a very thin and fine mist of water sprayed into the engine intake while it is revving very high. I have doen this dozens of times on my high mileage cars with no problems but it can be catastrophic if you don't do it right.
  7. BigDaddyT

    BigDaddyT Member

    Yeah a tablespoon or so of water down a carbureter while revving the engine on a car was fine. Wonder how much you could put into a little 2 stroke.
  8. Skyliner70cc

    Skyliner70cc Active Member

    I would probably use a spray bottle that squirts a fine mist of water. When the water hits the piston, it instantly boils which is supposed to knock out the carbon. You can technically put gallons of water, total amount is not important, what is important is the rate of water going into the engine.
  9. BigDaddyT

    BigDaddyT Member

    The way I was told was it explosively turns to steam and in doing so can remove carbon buildup.
  10. nsideus

    nsideus Guest

    Couldn't the loose carbon score the cylinder? I use to decarbon the exhaust ports on my lawn equipment and was always very careful as not to let any slip back into the cylinder. I ran a crew for a lawn company and told the owner his exhaust ports were probably clogged he decided to clean them himself and scored the cylinders.
  11. Mountainman

    Mountainman Active Member

    for heavy buildup -- head should be removed

    so as to get that carbon stuff out

    ride that clean MB thing
  12. Baverian

    Baverian Member

    Back to the sparkplug

    The plug will not burn a hole in a piston! This would be caused from the
    air/fuel mixture being too lean due to wrong jet size or a vacuum leak.
  13. Mountainman

    Mountainman Active Member

    I don't know ????

    just can't buy that -- till I hear more

    admitted -- when I worked in a small engine repair shop years ago
    seems that at times different plugs were put in
    and -- never saw an engine come back in for repair with hole in piston
    but -- I didn't work there that long

    anyway -- while down the mountain a while back at the local small engine shop
    wanting to buy a plug -- the guy had one that would fit
    but -- said that it also may burn a hole in piston
    this guy's been repairing small engines for a very long time

    I am going to hold back until we know more

    ride those things
  14. Baverian

    Baverian Member

    Last edited: Feb 4, 2009
  15. Mountainman

    Mountainman Active Member

    good information Baverian

    thanks for that information Baverian regarding plugs

    that's what was needed so as to bring some light to this subject

    when I posted this thread -- that was the reason -- wanting to hear more

    sounds like -- it is important to get the correct plug THING in there

    burning holes in pistons -- seems not
    when the guy told me that though -- I didn't want to play around

    put the PLUG in the JUG -- never thought about it -- double meaning

    rather get down and ride that motor bike THING