MOPED ARMY

Did you put the bing 15 on? What's your jetting?

It would be odd for such a mild build to slip timing but it is possible.

I would do a proper compression test. The finger test is bs. I have a feeling she soft seized it going down the hill.

Thanks all!

To answer a couple questions:

-yes, I put the 15 bing this spring on along with an estoril pipe (over built these components because I knew I'd like to kit someday). It has run just fine until the incident last night!

-I don't have a proper compression test, so sounds like I'll need to take it apart. Probably a good exercise as I haven't taken the time to do it yet.

One additional clue I thought of- I did get it to start just for no more than a 4-5 seconds. The rpms were unstable, revving up and down near idle and eventually just died.

Thanks again for the help, folks.

Not timed, tuned, Jetted correctly, not protected with a head temperature gauge, magneto not serviced , fuel flow compromised, wrong mix etc.

Basically you didn’t blueprint the whole build, Probably never changed the original seals and left every thing to chance so could’ve seized/so many things you could’ve done wrong,

Take everything apart and inspect it put everything back together with new gaskets,

Do a compression test, crank case leak down test, service the magneto, Point gap, time correctly, jet correctly, tune correctly,

bjaockx, that happened a few weeks ago, but was fortunately not the problem this time! Appreciate you asking though. Turns out I needed a new spark plug.

roffman, wouldn't it be nice to have all the time to do that! Hope to do that eventually. Thanks for the wisdom.

ggspeed, great idea! I'll have to remember that one.

Took the cylinder head off and found a rather crusty piston. I'm guessing it should not have this much carbon build up. The spark plug that fowled was an ngk b7hs, the new one I put in is a b6hs.

One one side of the spectrum, there is a carbon-y, oily b7hs and (in doing a plug chop) a much lighter colored b6hs. The ped felt faster today with the new plug. Perhaps because it is a "hotter" one. It looks as if I'll have to up-jet though because of the white-ish color. Can someone confirm I'm on the right track here for avoiding further plug fowling?

b7hs (old plug, after trying to clean it with a cloth)

b6hs (new plug after plug chop)

piston head during diagnosis, before installation of new plug

Yeah that b6 is a good color. Have fun!

Just my lame two cents worth, but I'm going with an ignition/wiring problem. If you can, replace all the ignition stuff so you can rule those things out, like your points and condenser, maybe even the coil and spark plug wire and cap. Keep the old ones, but until you know for sure about all that, the rest of any diagnosis is pretty difficult. Make sure your magneto coils are looking clean and no issues with wires grounding that shouldn't as they wind around and through all sorts of possible places for shorts to happen when wire insulation fails. Heat does a lot of weird things to ignition parts as well as induction, so double check that you have a good o-ring in your carb jammed up against the intake since heat can open up air leaks. All basic stuff, but good for all of us to say these things for the sake of others hopefully doing their research here and who have similar problems.