Honda PA50II complete fuel loss frustration

Hello all,

I recently bought a used PA50II from ~1978 (yellow in color) that was said to run well once working. Indeed when it ran it had a surprising top speed and power. However the problem is that the motor, no matter how many times I pedal to turn over the engine, doesn't seem to spray atomized fuel/air into the engine. So the procedure is Fill carb with new premix > pedal like crazy with decomp and then release decomp and continue pedaling > take out spark plug to see if there is any fuel odor or visible liquid. There is none. This entire time the muffler is off. SPARK is good, compression blows my finger off the cylinder.

I thought the problem was poor jetting cause of the crappy old carb so i bought a NEW carb of a style that I know works and hooked it up. Amazingly the moped started right up and gave me all the power i ever dreamed of. That was the only time it ever worked. I cannot get a moped working With known good Carb, Spark and Compression. Why isn't fuel getting into this thing???'

thanks in advance

Re: Honda PA50II complete fuel loss frustration

Also forgot to add that fuel system is new - petcock, filter, tubes.

Re: Honda PA50II complete fuel loss frustration

Leon Swarmer /

Mike, You said you filled the carb with new premix. Unless you've pulled off the bowl. or drained a little out from the bottom, you may not know that you filled the bowl. If the needle valve is stuck closed the fuel may not go into the carb.

Re: Honda PA50II complete fuel loss frustration

This does seem like a good place to poke at since the problem is with fuel flow... The carb as a priming button...i have held it in until fuel flooded over the float bowl into the mixing chamber, but still nothing. I have used this model carburator (4 of them!) on several bikes over the years and find them to be beyond extremely reliable - instant start ups every time. Similar to your line of reasoning I thought the needle wasnt reaching down into the bowl but when i pull the throttle assembly apart there IS ample fuel coating the needle like there should be. Its almost like there is a blockage somehow.

Re: Honda PA50II complete fuel loss frustration

Possible crusty rusty tank? rust may be pluging prior to the petcock? loos intake pipe too much air.... no gas/ just some thoughts...good luck! My pa 50 II runns perfect with original carb...but they must be spotless!!!!!!!!!!!!!

Re: Honda PA50II complete fuel loss frustration

I would go back to the starting point.

Totally clean the original carb. Even to teh point of taking out the brass mixing tube that is located in the center of the throat.

Clean everything spotless. Run a fine wire thru every orifice you can find. Then spray carb cleaner thru every orifice also.

With float bowl off, check for fuel flow by hooking up the fuel line to the carb. You should get a steady flow of fuel out of the float jet. Put the float bowl back on. the drain screw should be on the right side. It is possible to install the bowl backwards . If you do install it backwards ti will force the float closed. (been there, done that.)

Reinstall carb and you should be good to go.

Re: Honda PA50II complete fuel loss frustration

Justin Campbell /

I agree with Silverfox. The carb is the most likely suspect. I had to clean mine a few times before it ran or idled correctly. Take your time and make it spotless. I always use non-hardening hi-temp gasket maker like permatex around the intake and reed valve, just to eliminate vacuum leaks. Should run like a champ after that though.

Good luck. Hobbits rule.


Re: Honda PA50II complete fuel loss frustration

this was the first thing i tried. i spend days on that was hopelessly gunked. Plus i was frustrated cause i didnt understand the needless design. It never fired on old carb

Re: Honda PA50II complete fuel loss frustration

I like the vacuum leak might explain why a new carb would possibly fire and run fine, then vibrate out of possition somehow...The seals were made with a thin layer of plastic epoxy, they are air tight...The last noise i heard before the bike died was a you think that means anything?

Re: Honda PA50II complete fuel loss frustration

i really like this suggestion. Fuel flow is no problem, and given that the fuel and carb systems are brand spanking-new, fine rust particles from the tank would explain how this could cause the new carb to fail after 10 minutes of riding.

Do you think rust could make it through a cheap petcock filter?

sometimes i get the feeling that the engine has a very fine tolerance for fuel/air choking and that it causes startup difficulties.

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