Small Engine Repair: Honda GX31 Motorized Bicycle Engine Walbro Diaphragm Carburetor Rebuild


**Always follow the instructions in your repair manual when doing repair or maintenance work on Outdoor Power Equipment. Manuals can be found at the manufacturers website.**

In this video I rebuild the Walbro carburetor on a Honda GX31 4 stroke engine.

Thank you for watching!



38 thoughts on “Small Engine Repair: Honda GX31 Motorized Bicycle Engine Walbro Diaphragm Carburetor Rebuild

  1. Good job
    I didn't realize the repercussion of carb cleaner in the little carbs I'm guilty of over cleaning w it
    Lesson learned forgotten tomorrow lol

  2. Excellent video, very well explained, keep up on the great videos. I would like to see you
    rebuild one of those small motors.

  3. The only two things I see that I would do differently, I would have a nurse look at that booboo on my hand, and I would change out that purg bulb. Thanks.

  4. Hi enjoyed your great illustration video. I recently installed a carb kit on my gx22.
    but it did'nt help with my problem. It idles great but really hesitates or bogs and quits on throttle up.

  5. Great video. Recently cleaned out my carby after the motor was submerged in a flood. The fuel pump diaphragm spring fell out without me noticing. Noticed the extra on assembly. Where did it come from? Your video showed me where to return it. Thanks.

  6. Thanks to your video, you probably saved me from countless wasted hours of my life, helped me to not learn 10 more cuss words and several shotgun shells from blowing up Walbro Carburetor. I watched it twice, only the second time with a beer. I took it all apart, which really wasn't that much but I had the confidence from watching your video. Breezed right thru it all. Can't wait to crank it up, can't do it now, its about 2am, ??? on the other hand. hehehe Hey thanks….You Da Man!!!

  7. I'm Still working on this thing. rebuilt the Carb exactly to your specs. New carb kit, fuel lines, bulb, fuel filter, air filter, adjusted the valves, put in new spark plug, new fuel and still idles ok but BOGS upon acceleration. Today while it was running, I sprayed the black throttle body with the adjustment screw and the engine would instantly die. Throttle body doesn't seem worn out, so I took it all apart again for the 6th time, put all back and still the same. Bogs on acceleration. help?

  8. Which was why the tines weren't turning, not enough acceleration to turn them. Checked out a friend with same model and his sounds like a Chain Saw. I soaked the carb bodies, blew can air through all the holes and ports. double checked the float level. 61 on the nose. I really hate to buy a new carb because I really want to troubleshoot this one. Any advise?? Thanks …Ron

  9. Great video. Really knows his stuff. I found my problem in the small filter screen which was totally clogged … don't ignore this vital part when you rebuild your carburetor.

  10. Great video. I much appreciate the effort and detail. I have an exploded diagram of the WYL carb, but nothing like seeing exactly where the springs are, or should be, and seeing how to deal with the needle valve. Helped me rebuild a WYL on a Honda Harmony tiller with a lot less anxiety. Even better: I did not have to remove the throttle stop; I was able to slip the line off the throttle lever by just moving the throttle lever down.

  11. Thank you for posting this video, found it incredibly helpful! You may want to change the title to "Honda GX31 carburetor overhaul" so people can find it.

  12. If you look at the carb at 9:02 and look at the fuel intake hole (where the mesh screen/filter is). That's where the gas goes in from the gas line. Afterwards it goes into the smaller hole directly under it. After that it goes into the slightly bigger hole that is located under and to the left (7:30 a clock). From that hole the gas goes into the slightly smaller hole that is located under and to the right (5 o'clock). What baffles me is that that last hole is covered by a little tab on the black gasket. How does the gas get into that hole if the hole is covered? Put the gasket on and see for yourself, a little tab sticks out and covers that last hole.

  13. I also did a test to see if the gas can somehow get through even though the hole is covered. I put the gasket in between the two carb halves and blew air through the fuel intake fitting and it was all sealed up, no air escaped any where. ???

  14. Another excellent video. I believe that is a Walbro WYC rotary style carb. Unlike many such units, WYC's have no accessible hi and low speed screws. Where there would be such screws on other rotary carbs, there are what look like little "bb'.s" blocking access to what may be said adjustment screws. I suppose this to prevent the consumer from making adjustments. Do you know how to remove the bb's so that the adjustment screws (if there are any there) can be accessed? 

  15. very helpful. a guy at work let me borrow his tiller with one of these, and when it bogged and wouldn't crank i was scared i'd have to buy a $300 replacement. took it apart, cleaned it up(i think a port was clogged with trash), cranked right up, returned it immediately 😛

  16. How do you know which kit to buy? I have the very same carburetor as the one shown. I tried search online with the numbers on it, they are WYL 70A025 any thoughts?

  17. Thanks for the video.
    A question: I lent my Gx31 weedeater out, and premix got ran through it. It now bogs under load. Tried the plug- no go.
    Could a carb rebuild be in order?


  18. Great help! That's a WYL? Very close to my WYC-27-1. I wonder if the L stands for 'lip' on the air intake?

    You can buy an aftermarket carb replacement for this on eBay from China for less than $13. I just swapped my Walbro on a Hitachi RB24EAP blower for a RuiXing I had sitting on dead equipment and it works fine.

  19. Actually there is a smal flat headed adjustment screw where the gas wire is located, it's inside the center hole of the plastik. Adjusts the fuel ratio.

  20. Hi small engine shop, i have a GX 35, and people say that if you drill the main jet bigger, it would increase the power, is this true? Will there be any disadvantages? thanks.

  21. On the fuel pump spring side of the carburetor body there's a small recess with a square shaped material that has a hole in the center. It can barely be seen at 15:03. You don't mention it in the video and parts diagrams don't mention it. Any idea what it is?

  22. My issue with this style of carburetor is the throttle ramp that lifts the rotary valve as it turns. It is there to lift the metering pin out of the main nozzle at the throttle is opened thus allowing more fuel flow. As that ramp and plastic pin wears down there will be less lift and the engine will eventually run lean.

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