4-Stroke Valve Spacing Guide

Discussion in '4-Stroke Engines' started by Earth Mechanic, Sep 18, 2007.

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  1. Hey Crew, Sorry so long since the last post, duty called. I have put serious mileage on my honda gxh50 4 stroke after regapping the valves (300+ miles) and found out that bigger valve gaps on the intake and exhaust is both easy to adjust and makes a big difference in accelaration and top speed (aka more of both). Follow the pics to regap your valves.

    I have also included pics of two gasket makers that will work, but are not recommended, as the red gasket maker has melted off my crankcase and head cover.


    Attached Files:

  2. MadPC

    MadPC Guest

    Hey Earth Mechanic, this is a great post... Thanks for being the few w/ the honda 4 stroke here.

    In fact I have the same engine too but I'm running into this "stalling problem" right now and i wonder if you have any advises for me.

    I get the engine brand new and I did not run for over 3 miles. One day I was trying to work w/ my gear box, I angled the bicycle 90 degrees up and some of the gasoline leaked out(I think it's from the carb)... then after that the stalling problem was introduced. The bike would stall while throttling...

    I then took out the the carb, cleaned it and rebuild it... the bike stalled even quicker then b4. I started it up, 2 sec later it died.

    I checked the fuel tank and filter, there is no clog..

    I checked the wiring, they are all good... the spark plug is good as well...

    So here is the question, when you get your new engine, after you connect the fuel input w/ the tank, did that take you a few days to let the fuel "soak" into the carb bowl? Or it happened instancely?

    This situation I have seems to related to low fuel in the carb bowl. So does it take the carb a few day make the gravity to push the gas down the bowl?

    I ordered and replaced the engine a new carb it's still no good. It starts for 2 sec and died. I wonder if I need to wait for the gas to soak into the carb bowl...

    Would the carb gasket blocked part of the pressure regularing holes? would that matter?
  3. HoughMade

    HoughMade Guest

    I have the GXH50 not installed yet. I was able to test run it by filling the fuel bowl with a syringe, then it would run until the bowl emptied. I did this several times. It sounds to me like your float is stuck or wedged in some way. However, it would seem that your carb rebuild would have addressed that...unless all your work was internal to the carb and not in the bowl.
  4. MadPC

    MadPC Guest

    hey where did u syringe the gasoline to? the main gas nozzle or the fuel valve?
  5. Dockspa1

    Dockspa1 Guest

    You put a whole new carb on or just the rebuild kit?
  6. MadPC

    MadPC Guest

    I did both...
    I first try to clean it and rebuild it... the problem was still there... then I order one from ebay and put the new one there
    it's still the same...
  7. dave1490

    dave1490 Guest

    this doesn.t make sence. increasing the gap would give you less lift and deration.quicker for the bottem end but not more speed.the best way is to adjust when running to just befor the ticking stop,s to compensate for thermal expantion.
  8. Alaskavan

    Alaskavan Guest

    Hey Mad, are you getting fuel from the tank to the carb? If it's gravity feed, if you pull the fuel line off the carb, there should be a good flow of fuel. It should not take days to fill the carb.
  9. MadPC

    MadPC Guest

    yea the fuel come out fine if I pull the gas pipe out from the carb...
  10. thanks for the reply dev,

    It does seam like it would decrease compression by opening up the valves. I also really didnt change the spacing by more than .5 mills, so maybe im just smokin. It does seam like tighter valve gaps would create more compression and top speed....Do you really recommend adjusting the valve gap while running, seams like it wouldbe tough to get the feeler guage in there with all the motion, but perhaps i just ditch the feeler and adjust the motor based on throttle sound?? teach me more.
  11. HoughMade

    HoughMade Guest

    Where you pull the fuel line off the carb- not directly into the carb.
  12. EM
    You will get better power with a lose adjustment on your valves. Tight valves do not let the valve to seat the whole way. It is good to have a little "tick" sound.When I got my kit it was hard to start & had low power. The valves wrer tight from the factory. I also
    added a external fuel filter. That got rid of the carb problems
    keep it between the ditches/ miky/bikey mike
  13. fredbert

    fredbert Guest

    Did MadPC get his problem fixed, I am interested in the solution, thanks.

  14. Irish John

    Irish John Guest

    That's great info Earth mechanic. Thanks. My Honda dealer told me today that the gaps fopr both valves are .07mm for the GXH 50 and I presume that they are the same for my Huangsheng. Any comment?
  15. Irish John

    Irish John Guest

    Hey MadPc, it's just a hunch but my engine was cutting out intermittently for no apparent reason. If your motor has been suddenly cutting out either long term or split-second it may be the throttle end of your kill switch. My Grubee kill switch is the same old HT crud and it was causing symptoms like you describe. The connections weren't good enough and they kept breaking the circuit until it got too bad to ride the bike.
    I wrote about it on the thread below:
    Intermittent glitches are the pits.
  16. Herrmanator8

    Herrmanator8 Guest

    Hey, i recall that you said you turned the engine a full 90 degrees. do you think that oil got up into the engine parts like the cylinder and valves? that might be the problem...or your low oil meter might be cutting the engine short...

  17. Irish John

    Irish John Guest

    Well Herrmanator I swivel it regularly to about 55 degrees to change the oil but that shouldn't matter. Oil gets up into the valves cos it is supposedto.
    If you take the valve cover off you can see tiny droplets squirting upwards into the air to keep the rockers oiled. No I don't think the motor has oil in the cylinder that hasn't burnt itself off and the plug is clean. It had no real pulling power on hills from the outset before it had ever been swivelled to half vertical with oil in it. It's just a small engine that is a bit gutless on steep hills and great on the rest of the terrain. Doesn't like carrying a heavy load either cos when both paniers are loaded with shopping I have to take the flat road home.
  18. no reply to the valve spacing. Seams like there is a range at which the spacing can be set.
  19. Irish

    i had the same experience. maybe try the felt aluminum frame? I have gone minimal on my ride and that is what keeps it fast. but really, the irritating thing is the width of the motor in the frame. I cannot really ride the bike, and i mean i have been a cyclist for 15 years. That is why i am working on mounting my 4 stroke on a rear rack and getting a nice 3 piece crank set and a rear derailler.
  20. Irish John

    Irish John Guest

    The only way we can get a suitable Felt other than the MP in Australia is to get someone in the US to buy it for us and shipo it to us. Felt importer here wants $1500 to get a cruiser in specially for someone and the lead time is a year! Felt dealers here wear stockings over their heads when they sell you the bike so you don't feel so bad about the robbery!