Neptune Mighty Mite stalls when given gas

[lindy46]

I bought this little motor about a year ago and just now started working on it. It’s a single cylinder model WC1 from the 60’s. Looks like new. Has good spark, compression 65psi+. I cleaned the carb and she fires right up, and idles fine. However, when I push the throttle lever to speed it up, she dies. Seems like a link and sync issue. I looked at the throttle cam and it almost looks like its mounted wrong with the gradual increase part of the cam trailing instead of leading if that makes sense. When I advance the throttle from idle, it only takes a small push of the throttle to completely open the carb butterfly. Pictures attached. It looks like there is no adjustments on the cam, and I tried turning it around but there is no other way to mount it. Anyone have any experience with this motor?

[lindy46]

First pic shows it at idle, and second pic shows throttle nudged a little to the right.  Note carb roller butterfly goes from closed to wide open. The blunt edge of the cam is leading and immediately pushes the carb throttle lever all the way open.

[frankr]

I agree the butterfly looks wonky.  But I notice something else.  Could the spark plug wire be arcing out to ground when it goes up against the crankcase?

[lindy46]

frankr wrote:

I agree the butterfly looks wonky.  But I notice something else.  Could the spark plug wire be arcing out to ground when it goes up against the crankcase?

Good thought. The wire looks original and casing has some small cracks. Probably time to replace it.

[dave-bernard]

to lean on the idle?????

[jeff-register]

If you need spark plug wire it can be had at a neon shop called G.T.O. wire. It looks like plug wire & rated at 15,000 volts. Comes in many colors & get Hi-flex wire. Ut has many small strands of copper wire easy to solder & can be bought by the foot. Bet your wire is leaking like Frank spoke of.

P.S. If you get an arc to ground by the fuel line you are asking for a fire on the water, Please replace the wire to be safe.

[lindy46]

dave-bernard wrote:

to lean on the idle?????

Have it set at 1 turn out, the recommended start setting for Tillotson AJ carb. And I tried varying that setting with no success.

[lindy46]

I put a new plug wire on and that didn’t solve the problem. The moment the carb butterfly opens she dies. Time to pull the carb again. I may have to install an in-line gas filter as there was rust in the tank which I cleaned out as best I could. Possibly junk still getting through.

[jeff-register]

You can go to a chain saw store & get a 2 stroke filter.I bet you are correct. My motor home had a rusty tank & I added filters. It worked for a while but starting backfiring thru the carb & a 440 big block shot up a three foot flame inside the motorhome & I was trapped in the drivers seat, Scary big flame! Replaced the tank & filters to cure.

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