Honda PA50 II engine sounds

After a long-overdue carb cleaning, I was quite pleased to have the engine turn

over quite easily. But I am just a little concerned about the sound it's making...

I'm unfamiliar with what a properly tuned two-stroke should sound like (anyone have a reference audio recording they want to post?) , but I don't think 'putt putt _miss_ putt putt _miss_ ' is the correct sound an idling engine should make, and 'vroom vroom _putt_ vroom vroom _putt_' is right at high RPMs.

Now, it could just be due to splash fouling - I did a plug chop after running the engine slightly above idle for 5 minutes or so, and the plug was definitely splash fouled - and if so that should go away after a good long ride and a new plug, right?

Any pointers on how a moped engine should sound when properly tuned up?

Especially what idle should sound like.

PS: Easiest way to get to the carb is the "remove the hanger bolt and drop the engine on a block of wood" technique. The hardest way is to follow the machine shop manual and do a full separation of the front and back halves. Guess which one I tried first...

PPS: I discovered the hard way that the carb can be reassembled in two ways, one of which (reversed lower cover) leads to the float valve being stuck up and fuel spilling out the overflow. Of course, I found this out _after_ having put the engine hanger bolt back in...

Honda PA50 II engine sounds

.. oh, and one other thing:

PPPS: Don't wear a platinum ring while working with carb cleaner - the platinum appears to catalyze some sort of reaction with the acetone and other chemicals in the carb cleaner and form a corrosive. (acid or caustic I don't know, I just know it hurt like hell 'till I pulled my ring off).

Re: Honda PA50 II engine sounds

The putt putt miss putt putt miss deal at idle is normal for a two stroke. They all do this when not pullung a load.

Re: Honda PA50 II engine sounds

Ah. Thanks for the info. I was dreading tearing it all apart again.

Especially now that it starts so nicely.

Re: Honda PA50 II engine sounds

this engine's got reed valve intake.. So, a piston ported intake 2-stroke's "normal" four-stroking and misfiring at low rpm is eliminated.

There's no missing at idle if it's set up right .. my bike idles steady at very low RPM... And no misfiring at higher RPMs either. The stock bike is about as smooth and quiet as a sewing machine if it's in perfect tune.

Since you already went through the carb/fuel system, i'd first suspect a vacuum leak, particularly where the carb meets the reed valve intake block.. That joint tends to leak. It did on mine. Gaskets dry out and shrink and crack..

Spray a bit of Starter Fluid around the area.. a change in rpm indicates a vacuum leak.

A coating of Permatex 2 (non-hardening gasket sealant) on the offending gasket / joint will cure it.. but there's no cure for this freakin design where you gotta drop the engine to get to it.

Or it may be reed trouble.. I've played with the reeds and they are very simple.. easy to diagnose.

Either the stainless steel petals lay perfectly flat against their seals or they don't. If they don't, the misfire-symptom could be the result (some fuel mix is regurgitted backwards into the carb causing a rich-misfire). I haven't seen cracked petals but it does happen.. A close inspection will reveal whatever may be wrong with them. If you remove the petal screws for any reason, be sure to use LocTite on them when reassembling.

Lastly (should be firstly) try a new spark plug..

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