Huasheng 142F 49cc 4-stroke valve adjustment

Discussion in '4-Stroke Engines' started by Max-M, Jun 28, 2012.

  1. Max-M

    Max-M Member

    For the first time, I adjusted the valves on my Huasheng 142F 49cc 4-stroke. All of the information I can find leads me to believe that the proper settings for this little engine are: .003" intake, .004" exhaust.

    I've done a great many valve adjustments over the years (and all kinds of other work) on small- and large-block hot-rodded Chevy engines, so this was a pretty basic task for me. But, I was totally clueless as to which valve was the intake, and which was the exhaust!

    In the attached photo (looking at the engine from the left side of the bike), you can see the two valves. I decided that the left side valve (closest to the exhaust) was the exhaust valve, and that the right side valve (closest to the carburetor) was the intake valve.

    I made the two valve adjustments with my feeler gauge, after removing the spark plug and pulling the starter cord until the top of the piston was at its highest point in the cyclinder. Then I retightened everything.

    I replaced the valve cover, put the spark plug back in place, and drank a cold beer. Then I pulled the starter cord, and the engine fired up on that one pull. It idled as smoothly as I've ever heard it: I've got the idle set as low as possible, and it just happily rumbled with a very even tone. Previously, this engine would idle with a fair amount of variation in its RPMs. This time, it was dead-steady.

    But, when I took a test ride, I noticed a definite reduction in power. For example, pulling up a hill that never required pedal-help, I definitely needed to pedal.

    Any thoughts, anybody? Did I mix up the exhaust and intake valves? Wrong clearances?



    Attached Files:

    Last edited: Jun 29, 2012

  2. tom-fishing

    tom-fishing Member

    Max you have the valves right and the gap is right also. Just wondering if the engine was cold when you adjusted the lash?
  3. Max-M

    Max-M Member

    Yes Tom, the engine was completely cold. Could that be my problem? I just did a Google search on "cold vs hot" when adjusting valves, and it sounds like I should set the valves with a hot engine. But, that's not totally clear.

    Thanks for your help...
  4. tom-fishing

    tom-fishing Member

    You were correct to adjust them cold. Next question, are your feeler gauges metric or inch? .003 & .004 are in inch measurements. If you still are having a problem I would go back to square one again and double check everything. It wouldn't hurt the engine to lash them at .004 & .006, and try that. I'd try a new plug if you have one also.
  5. Max-M

    Max-M Member

    Thanks, Tom. My feeler gauges are marked in inches and millimeters. I'm going to try lashing the valves at .004" and .006", as you suggested.

    I installed a new NGK CR7HSA plug not too long ago, so I think I'm good there. I initially replaced the engine's original Chinese plug ("Torch" brand) with an NGK CR5HSB; the NGK plug that was listed as the correct plug for the Honda GXH50 (of which the Huasheng is a clone). The Torch plug wasn't giving me any problems, but I figured that an NGK would be better, and it's a cheap and easy upgrade. As it turns out, the engine didn't run as well with the CR5HSB. But on this forum, Quenton Guenther told me that there are some subtle differences between the carburetors on the Huasheng and Honda, and that a colder plug would likely be better in my Huasheng. So I installed the CR7HSA (with NGK, the lower the number, the hotter the plug), and I noticed a pretty positive difference from the previous two plugs.

    I'll report back after my new lash settings!
  6. The_Aleman

    The_Aleman Active Member

    Adjusting the valves is, IMHO, the most important thing you can do with these, as far as getting the most power and reducing engine noise.

    In the last 2 years, I've had my HS set from anywhere between .010./0.14 to 0.003/0.004 (it was in the 0.20s from the factory) and I think .003/0.004 seems tight on hot days.

    0.004/0.006" is what I set mine at now, seems to be the most consistent with Sacramento Valley weather (40-110 degrees).
  7. Max-M

    Max-M Member

    Thanks, Aleman. Yes, the loss of power that I experienced a couple of days ago after setting my valves to .003/.004 was pretty dramatic. I neglected to check the factory settings beforehand, but I guess I can assume they were more open than .003/.004.

    I'm going to reset to .004/.006 this morning, and we'll see what happens. We're expecting a real scorcher of a day here today in Connecticut; high heat and humidity. I wasn't really thinking about that additional engine-performance factor until you mentioned it. These forum "conversations" are quite valuable.
  8. Max-M

    Max-M Member


    Well, I readjusted my valves to .004" intake / .006" exhaust.

    This bike has never run better; pulls the hills nicely, and it seems a bit quieter and throatier in tone.

    Thanks for your help, gents.

    Attached Files:

  9. zwebx

    zwebx Member

    i got mine at 0.04 and 0.06 and whatnot its still knocking sound from the head, is it because i run premium fuel?
  10. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    That should be
    0.004" intake
    0.006" exhaust

    If 0.04" and 0.06" is what you set them at they are knocking
    because they are way too loose.
  11. zwebx

    zwebx Member

    i miss typed that... my bad .006 and .004 is what i have.
  12. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Try using regular gas, as higher octane requires a higher compression ratio to be of any help.

    When testing my Whizzers on the DYNO, all but one ran better on regular gasoline. The only one that was helped with the hi test fuel was a motor with 165 pounds of compression.

    Have fun,