Honda 50 lost compression

Discussion in '4-Stroke Engines' started by Fred Fry, Jun 24, 2010.

  1. Fred Fry

    Fred Fry New Member

    I am kinda baffled about what happened.
    I have a honda gxh 50 on a friction drive and this is my second year and it has been great.
    It probably has about 100 hrs. on it.
    It has always started on the first pull when cold with choke.
    Yesterday morning I pulled it 4 times and nothing.
    The previous day it was running great.
    I found it was getting gas and spark.
    I pulled the spark plug and put my finger over the hole and felt no compression.
    I poured a little oil into the cylinder and the compression got better.
    I put the plug back in and it started right up.
    Now it is starting again on the first pull like before.
    I have been running on synthetic oil.
    Were my rings carboned up and stuck?
    Should I put something in the motor to clean it out?

    Thank You Fred

  2. scotto-

    scotto- Member


    You may have had a valve sticking (open or closed), but a ring sticking would be a seizure of such and oil wouldn't improve the compression much in that case. Valve sticking...perhaps.
  3. GearNut

    GearNut Active Member

    I would add 1/2 a teaspoon of Marvel Mystery oil to it. It helps clean out carbon gunk from the ring lands in the piston, and any carbon or gunk built up around the valve guides.
    Do not use too much! If misused, it can do more harm than good.
  4. Old Bob

    Old Bob Member

    Stuck rings don't loosen that quick.
    I don't recommend putting marvel in that engine. It uses splash lube and has no filter. Marvel is high detergent,it will loosen particles and gunk only to have it redistributed in other places.
    Pull the valve cover and see if there any build up,varnish etc.

    Hard to beleive running syn that theres gunk built up already.
    How often do you change it?
    When was the last time you adjusted valves?
  5. Fred Fry

    Fred Fry New Member

    Hi old bob,
    I adjusted the valves about 2 weeks ago.
    They were sloppy like one was .008 and the other was.012.
    I adjusted them to .003.
    Everything looked clean under the valve cover.
    She's back to her old self starting on the first pull.
    I am thinking something caused the valves to stick open.
    I have heard running some trans fluid for a short time and then to do an oil change.
    I change the oil often. It takes very little oil and the cost is minimal.
    Thank You
  6. Old Bob

    Old Bob Member

    I've seen this on a couple of engines with some hours.
    Its possible for the exhaust valve to stick if it had been running with a lot of lash, a ring of varnish forms on valve stem, when the lash is tightened the ring is pushed into guide and can stick valve, most of the time the ring rubs off and everything is ok.
    This could be a possibility in your case.

    If the engine is fairly clean then regular cleaning with marvel or ATF will keep it clean and won't hurt it.Only when theres sludge build up that I would avoid it, in that case I pull it apart and clean it in degreaser.
  7. unior

    unior Member

    old bob:

    is the head gasket reusable on this engine and/or the huaseng 50?
  8. Old Bob

    Old Bob Member

    GXH50 does not have a head gasket,the head is integral with cylinder/crank case.
  9. unior

    unior Member

    Ooops, duh. How difficult is it to remove the valves? How much dissasembly is required?

  10. scotto-

    scotto- Member

    Complete dissasembly

    It's not that difficult to remove the valves, it's a lot more difficult putting the whole engine back together without the knowledge, the proper tools, a shop manual and a good memory. You have to split the crankcase halves to access the valves which means almost complete dissasembly of the engine.

    It's really not that hard if you know what you're doing. :whistling:
  11. Old Bob

    Old Bob Member

    I posted links to the shop manual and the IPL a while back.
  12. unior

    unior Member

    Old bob you have a shop manual for the HS?

    I searched and couldn't find it.

  13. Irish John

    Irish John Guest

    The correct clearance for the GXH50 is inlet 0.06 - 0.10mm and exhaust 0.09 - 0.13mm
    You shouldn't have to touch the valves on a Honda and certainly not in the first 100 hours of use. Are you talking Honda or are you HuaSheng? If your gearbox is one of those new Grubees it will cause your engine to rev at max just to go at a steady 25 mph and that will cause problems fairly quickly. I use the oil manual recommends. Honda recommend it for a good reason.