Bad Head for sale on Amazon

J

Joeltrain1973

New Member
I wanted to let y'all motorized bikers know about a purchase I made that turned out BAD. I purchased a cnc aluminum cylinder head, spark plug and banana expansion chamber on Amazon for $21. I did not immediately realize that I had a problem as I also installed some new electrical parts at the same time, but my 66cc Jet motor developed a pretty major misfire under load. I changed every single replaceable part on the thing trying to get rid of the misfire, except the head. Carburetor air filter fuel filter magneto cdi spark plug wire kill switch intake manifold and muffler as well as carb jets had no effect. I put my old head on and viola back to normal. I'm not upset at all as what i really wanted was the muffler and that was a good deal alone for $21. I have attached a picture of the culprit to save you guys some grief. I don't kmow why this thing caused such a misfire as I cannot find anything physically wrong with it. It is not cracked and was seated to the gasket perfectly. I guess it could be my head was a slant plug head originally and this is a straight plug config but ??
 

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I have that head on one of my engines and it runs good, the problem may be the sparkplug, I run a ngk 7 range.
 
One thing I’ve learned over the years is no two engines are exactly the same or run the same. I’ve built four bikes exactly the same and one is always better.
 
I had a similar problem with one head running badly and another perfectly on the same engine. Turns out the bad running head has a larger combustion chamber which caused all sorts of grief with the lower compression. Bet yours is the same.
 
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