Re: 15hp won't start on it's own
Howdy,
The automatic enrichment valve or "bystarter assembly" (as Honda calls it) COULD be stuck but I've never seen one fail in almost six years. The valve is defaulted in the START (retracted) position and is then extended against spring pressure as the engine runs and charges. If it were to fail electrically, it would allow easy starting but then would cause the engine to bog on a rich mix. Exactly the opposite of your problem. You can check it's operation by removing it and applying 12vdc to the plug terminals and verifying that it slowly extends after about a minute and then slowly retracts as it cools down after the current is taken away.
My guess is that you will find it working ok. My guess is that your carb still has dirt in it somewhere.
You have to take the carb off to check the bystarter anyway so disassemble the carb again and look really hard at all the circuits. Find the accelerator circuit in the main body, prop the throttle plate wide open and spray carb spray into the accel pump passage and verify that about a 4FT. stream of spray exits at the rear of the carb.
Take the JET SET out and, using the plastic straw that came with the can, insert it into the passage at the top of the carb throat and verify that all three orifices at the top of the throttle bore are "gushing". Closely examine the drilled portions of the jet set tube as well as the interior "tunnelway" and make sure you see light. That tube can be clogged by some pretty tiny particles.
The only real way to properly clear the idle circuit passage ( orifice on the engine side of the closed throttle plate) is to remove the idle mix screw and back flush several times. This may be your problem area as the engine starts and runs after an ENGINE KILLING spray of ETHER. As a mechanic, I HATE that stuff! Should only be used if you're SINKING. I digress.
Getting the idle screw out usually requires that you break the screw head to get the limiter off so you should have a new one on hand before you start. Sometimes you can heat the limiter cap with a soldering iron and get the screw out without breaking it though.
If you re-used the oring at the top of the JET SET tube, bAAAAAd. Always use a new one there and re-install with a coat of WD-40 and much care. That is a critical junction.
If you don't regularly drain your carb USING THE DRAIN SCREW provided for that purpose, you passages in the bottom of the float chamber may be plugged. Study them and make sure they are open and will pass a shot of carb spray through the "tunnel" easily.
If you do all this, that puppy will start right up after you bolt her back on.
Good luck,
jimmyd
