GY6 Valve Adjustment Guide

Valve “lash” is the technical name for the gap between the valve and tappet.  The lash is critical to a healthy running engine.  Too little lash and you’ll see starting problems and reliability issues.  Too much lash will reduce power and potentially ruin the valve.

Adjust the valve tappets to a clearance of:

  • Intake 0.002″ – 0.004″
  • Exhaust 0.003″ -0.006″

How-to: Adjust your Valves

If you’ve just replaced the camshaft, make sure it’s properly timed.  You’ll need a set of 0.004″ and 0.005″ feeler gauges, and a 9mm wrench.

Start by getting familiar with your valve and rocker assemblies.


  1. Loosen the tappet locking nut on the top of the tappet and turn the tappet out several turns.
  2. Sandwich the 0.004″ feeler gauge between the bottom of the tappet and the top of the valve.
  3. Tighten the tappet while moving the feeler gauge back and forth until you can feel a slight drag on the feeler. Then carefully re-tighten the locking nut.  You may need a set of pliers to keep the head of the tappet from turning.
  4. Repeat for the remaining valve.

Check your work!

It’s important now to recheck the lash of each valve.  Rotate the crankshaft a couple times and run the 0.004″ feeler gauge through again.  Then try to insert 0.005″ feeler.  If it doesn’t fit, you’re set properly.

12 thoughts on “GY6 Valve Adjustment Guide

  1. Ron Brown

    Is the gap set at .05mm on the 50cc engine?

    • Buggy Depot

      Hey Ron, we don’t have lash gap data here on the 50cc version of the GY6, as we deal solely with the 150cc.

      A quick search on Google did suggest 0.002″ Intake and 0.0025″ Exhaust for the 50cc, but I recommend more research before breaking out the wrenches.

      • mark Lizama

        I have a 162QMK gy6 motor does this apply to mine aswell?…
        Please contact me through my email thanks

        • Travis @ Buggy Depot

          Yes, it’s the same process and spec.


      thank u alot for the help i tryed 6 different timing methods and yours was the only one that helped me i have a bintelli havoc gy6b 150cc bike got it from a friend and he striped the spark plug threads so i rebuilt the top end and replaced the piston and rings rebuilt the carb it had 14.000 miles on it again thank you

  2. John

    I have a yerf-dog 150 cc I have spark and its getting but will not start. Do I need to dig deeper into engine?

  3. TKeagle

    John, I had the same problem. Couldn’t figure it out. I just put in a big bore kit, and cam. I had spark. And had gas going into the carb. If I remember right, I gave it a shot of starter fluid. And it turned over. Little more looking, and found out that the brand new spark plug I put in, was defective. It gave spark. But not enough. Put my old spark plug back in, and fired right up. (took a few weeks to figure out. ) 🙂
    However, I would suggest that your carb is good and clean. A shot of starter fluid might let you know if your missing something in the Gas/air/ spark mixture.

  4. TKeagle

    Have question of my own. As stated ealier, I installed 58.5 bore kit, and A12 cam in 150cc. I set both gaps at .004. It seems to run good. But I do have some back fire in it when I run with a open header. When I put on the muffler, it doesn’t back fire anymore. Does the engine need the muffler’s back pressure? Or do I have my gap’s set wrong? And of course, I could be light on my gas mixture. Just some fine tunning I would like to do, if can. And wondering if my gaps are wrong. Really cant find anythig soild on what to set them at.

  5. Gary Headlee

    I’ve been doing this whit for. 50 + years, perfect example and explanations.
    I get so tired of those time streched time waisting YouTube videos. Kudos for the good teaching work!

  6. Ben

    Awesome sight by the way! What I need to know is exactly what I have. I got this from a neighbor and I just don’t know what the name of it is how to find out .
    obviously it’s chinese-made and I believe the company that made the this particular model is no longer in business or has changed its name and it’s making something different. problem is I don’t know how to send you a picture of what I have without having an actual email address.

  7. Jim Herbert

    I have a Ledgen 2019 – 150cc with 7000km on it and want to check valve lash. Do your measurements apply to this engine as well? Do you also do it with engine cold or hot ? Might sound like a silly question but I have heard both. Thanks

    • Travis @ Buggy Depot

      If your 150 is GY6-based, the valve lash specs above will apply. Definitely cold engine only.

Leave a Reply

Your email address will not be published. Required fields are marked *