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,
  13. Chris L

    Chris L Guest

    I recently was riding home after work and my chain completely snapped, I immediately pulled over turned the engine off and went and got my chain off the street. It was crazy cause it literally snapped a link and not master link. So peddled myself 10 miles home. Whew!

    I have a Huasheng 49cc 4 stroke, then since the chain snapped and I don't even have 50 miles on bike yet. So decided to adjust the valves now since, it was bogging down on full throttle but would be smooth at about 75% throttle.

    Took the valve top off, moved the piston to highest point then went to adjust the valves the intake was easy but the exhaust valve seemed stuck to tight. I tried all ways of loosening it and it wouldn't loosening up at all. I then put the NGK 7 spark plug back in tightened down everything and even took the carb off with SBP air filter cleaned everything really well, made sure the jet wasn't clogged or anything put it all back together.

    I then proceeded to go take it for a test ride and seemed my pull start was super loose like almost way to easy to pull, it would retract fine. I tried putting some starting fluid in carb area and still nothing, changed spark plug back to original and same thing would turn over. Removed the pull start to check seems everything is fine minus how loosely the flywheel turns without any pressure. Last night I opened the valve top again to see if I could get the exhaust valve to adjust and still stuck really tight. Anyone have any suggestions on how to fix/repair? I'm going to contact the supplier I got the engine from and see about returning it. But more than likely anticipating they won't.
  14. gary55

    gary55 Well-Known Member

    Maybe you got that intake valve adjusted a bit to tight. Staying open to long into the compression stroke would make her spin easier on the pull start.
  15. jeff bike

    jeff bike New Member

    All u guys thanks someone mentioned going back to regular gas,my motor runs very fantastic but was knocking on preium so back on regular no pinging sound and still a strong motor
  16. Nanonevol

    Nanonevol Member

    Knocking on premium, but ok on regular? You sure about that?
  17. jeff bike

    jeff bike New Member

    Its only change I made back to regular
  18. jeff bike

    jeff bike New Member

    I run a 4 stroke, only change i made was switch gas
  19. CrazyDan

    CrazyDan Active Member

    Sounds backwards, "premium" has a higher octane so less chance of predetonation. My 144f has higher compression than a 142f so i need higher octane to not ping. I hate the term "premium" when its a less pure gasoline...more additives to raise the octane level...
  20. KCvale

    KCvale Motorized Bicycle Vendor

    Exactly correct.
    More octane is not some performance booster any more than WD-40 is a lubricant.

    A verified real performance booster you actually feel on these ~50cc HS 4-strokes is an NGK 7544 (CR7HIX) for the summer and an CR6HIX for winter spark plug.
    Beside a bigger spark they a physically longer giving you a bit more compression ;-}

    I see you are liking your 144F Dan, I know it's only 4cc larger that 142F but man, you can you feel that 4cc's difference.